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General => General Chat => Topic started by: Homer J Simpson on October 29, 2018, 07:54:41 pm

Title: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Homer J Simpson on October 29, 2018, 07:54:41 pm
Will be interesting to see where this goes.

"A technical log obtained by the BBC from the plane's previous flight suggests that the airspeed reading on the captain's instrument was unreliable, and the altitude readings differed on the captain's and first officer's instruments."

"Identified that CAPT [captain's] instrument was unreliable and handover control to FO [first officer]," the log reads. "Continue NNC of Airspeed Unreliable and ALT disagree."


https://www.bbc.com/news/world-asia-46022390 (https://www.bbc.com/news/world-asia-46022390)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rx8pilot on October 29, 2018, 08:06:21 pm
The level of redundancy and fault handling automation in a brand new 737 is pretty amazing -, especially on airspeed and altitude.

Patiently waiting to see what happened. I could have been similar to the Air France crash where a relatively minor malfunction led to auto-pilot disconnect and the pilot reacted inappropriately to the situation. Failing gauges in real life are really challenging to understand and react properly.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on October 29, 2018, 08:23:48 pm
I see 737's have issues with their five(!) pitot tubes as well, going back a few years.
http://aviationweek.com/awin/boeing-addresses-pitot-tube-anomaly-its-737s (http://aviationweek.com/awin/boeing-addresses-pitot-tube-anomaly-its-737s)

I don't understand why heating a pipe is so difficult to engineer, redundancy doesn't help and there are still crashes happening from a corrupted sensor.

Pic "thermal imaging of a partially shorted pitot probe {heater?} shows that heat (red) does not reach the tip, where ice can form and corrupt airspeed measurements". (Credit: Irish Air Accident Investigation Unit)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SiliconWizard on October 29, 2018, 08:34:11 pm
Have not yet enough info on this to get an idea of what would have happened, but I don't agree with the general claim that crashes "happen from a corrupted sensor."

That's sometimes the starting point, but almost never the real cause. Unless the plane is already at a very low altitude (on approach for instance) with low visibility, a bad airspeed indication doesn't itself cause a crash. An experienced pilot knows 1/ how to spot a defective pitot when it happens and 2/ that the best way of dealing with it is usually not to do anything until the measurement gets back to normal. Unfortunately, a lot of airline pilots are not as experienced as they used to be or as they should be, and sometimes they will act irrationally on commands until the plane stalls. That's pretty much what happened with the (in)famous Rio-Paris flight, for instance. The reports are all publicly available.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rx8pilot on October 29, 2018, 08:58:11 pm
Unconfirmed information suggests this crew was rather experienced.

I had a pitot tube clog on an IFR flight in a single-engine airplane about 10 years ago. The hard part of identifying the problem is that it came on rather slowly. The aircraft only had a single tube, but the pitch, power, altitude, and temp of the aircraft did not agree with the number I was seeing. My reaction was to keep the wings level, the pitch level, and the power constant while I tried to understand what was happening. Once I was pretty sure there was no fixing it - I called ATC to help get me out of the clouds with a very slow decent. All ended well, but much more confusing and intense than my training ever suggested.

The systems in a 737 are massively more complex and I believe they have an automatic reversion when a single system is out of agreement. Even if it does not, the identification and response to a pitot/static error or total failure is among the most rehearsed emergency in my experience. Perhaps less so in the heavy iron aircraft with all the redundancy.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on October 29, 2018, 09:09:57 pm
Air France 447 was a night flight in heavy rain.

Lion 610 was a morning flight in what appears to have been VFR conditions. Yes, there were clouds, but weather was reported good enough (2000-and-5) that student pilots could have been out soloing airplanes in it. You can't comfortably fly a transport jet solely by visual references, but you ought to be able to keep it out of the water, IMO.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on October 29, 2018, 09:26:03 pm

I had a pitot tube clog on an IFR flight in a single-engine airplane about 10 years ago. The hard part of identifying the problem is that it came on rather slowly. The aircraft only had a single tube, but the pitch, power, altitude, and temp of the aircraft did not agree with the number I was seeing. My reaction was to keep the wings level, the pitch level, and the power constant while I tried to understand what was happening. Once I was pretty sure there was no fixing it - I called ATC to help get me out of the clouds with a very slow decent. All ended well, but much more confusing and intense than my training ever suggested.

Keep flying the plane in a configuration you know works.  That was the experience I was given by two very high time old timers that were my instructors.  AFR447 was an example of doing the opposite.

I'm sure we'll find out why this plane went down, but all of the people  immediate jumping to conclusions is just silly
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: nctnico on October 29, 2018, 09:29:52 pm
Have not yet enough info on this to get an idea of what would have happened, but I don't agree with the general claim that crashes "happen from a corrupted sensor."

That's sometimes the starting point, but almost never the real cause. Unless the plane is already at a very low altitude (on approach for instance) with low visibility, a bad airspeed indication doesn't itself cause a crash. An experienced pilot knows 1/ how to spot a defective pitot when it happens and 2/ that the best way of dealing with it is usually not to do anything until the measurement gets back to normal. Unfortunately, a lot of airline pilots are not as experienced as they used to be or as they should be, and sometimes they will act irrationally on commands until the plane stalls. That's pretty much what happened with the (in)famous Rio-Paris flight, for instance. The reports are all publicly available.
Same here: https://en.wikipedia.org/wiki/Turkish_Airlines_Flight_1951 (https://en.wikipedia.org/wiki/Turkish_Airlines_Flight_1951) and also a Boeing 737 with faulty sensor readings.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on October 29, 2018, 09:39:50 pm
There's so many pitot tube incidents. I question the airplane's software algorithms, a pitot tube reading wrong seems to generate alarms that confuses the crew and causes a lethal panic. The software should be able to estimate from the other sensors or roll back to GPS for speed, or just stop issuing a fake airspeed if you know the sensors have failed and can't make a concensus.
 
737
"Three of the probes are on the nose for airspeed measurements—for the pilot, the co-pilot, and as a backup—and two are on the vertical stabilizer for the elevator feel-and-centering unit. If the airspeed difference between the pilot and co-pilot probes is greater than 5 kt. for 5 sec. consecutively, the pilots receive an “IAS (indicated airspeed) Disagree” alert. "

"A man with a watch knows what time it is. A man with two watches is never sure." (https://en.wikipedia.org/wiki/Segal's_law)
You can't take a concensus with two sensors.
So captain and co-pilot are lost as to the airplane's true speed but the backup sensor does nothing?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: jpanhalt on October 29, 2018, 10:15:18 pm
Unconfirmed information suggests this crew was rather experienced.

I had a pitot tube clog on an IFR flight in a single-engine airplane about 10 years ago. The hard part of identifying the problem is that it came on rather slowly. The aircraft only had a single tube, but the pitch, power, altitude, and temp of the aircraft did not agree with the number I was seeing. My reaction was to keep the wings level, the pitch level, and the power constant while I tried to understand what was happening. Once I was pretty sure there was no fixing it - I called ATC to help get me out of the clouds with a very slow decent. All ended well, but much more confusing and intense than my training ever suggested.

The systems in a 737 are massively more complex and I believe they have an automatic reversion when a single system is out of agreement. Even if it does not, the identification and response to a pitot/static error or total failure is among the most rehearsed emergency in my experience. Perhaps less so in the heavy iron aircraft with all the redundancy.

Almost same thing happened to me in 1975 or so.   Piper Arrow.   Moral is that airspeed, while very important, is not the only indicator of the aircraft's airspeed.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Macbeth on October 29, 2018, 10:32:13 pm
This plane was brand new, just entered service in August.

Apparently Lion are considered shit - possibly even worse than Ryanair if that is even possible, like they actually charge budding pilots money to fly their planes instead of paying them!!  :palm:

But the pilot of this plane was a pro and had at least 6000 hours flying experience.

Terrible incident for all involved. Damn. We need answers.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: jpanhalt on October 29, 2018, 10:40:27 pm
This plane was brand new, just entered service in August.

Apparently Lion are considered shit - possibly even worse than Ryanair if that is even possible, like they actually charge budding pilots money to fly their planes instead of paying them!!  :palm:

But the pilot of this plane was a pro and had at least 6000 hours flying experience.

Terrible incident for all involved. Damn. We need answers.

Sure, just like we got for MH370!   Complete disinformation from the authorities who are more interested in their jobs than saving lives.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rx8pilot on October 29, 2018, 10:52:50 pm
Boeing may be the best source of answers on this one. Since the plane is so new - ALL of Boeings customers and the NTSB are going to be asking a pile of questions.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on October 29, 2018, 10:56:00 pm
For those interested in this stuff I highly recommend the book QF32
The captain takes you blow by blow through what it's like to get multiple conflicting warnings and whatnot

https://www.amazon.com.au/QF32-author-Life-Lessons-Cockpit-ebook/dp/B007KTLQ5W (https://www.amazon.com.au/QF32-author-Life-Lessons-Cockpit-ebook/dp/B007KTLQ5W)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Mr. Scram on October 29, 2018, 10:56:28 pm
Sure, just like we got for MH370!   Complete disinformation from the authorities who are more interested in their jobs than saving lives.
They found the aircraft, so that seems unlikely. The stakes are much too much for it to be brushed under the carpet.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on October 29, 2018, 11:29:41 pm
... or roll back to GPS for speed, or just stop issuing a fake airspeed if you know the sensors have failed and can't make a concensus.
GPS shows ground speed, not air speed. Not entirely useless, but they're usually not the same number.

The IAS alert will tell the pilots the left and right numbers don't agree. Odds are one of them is correct, so letting the pilots know the readings is still useful. They have airspeed unreliable procedure, which involves turning off the autopilots and putting the plane in a particular power and pitch setting to maintain airspeed, at least until they evaluate the problem.

Quote

737
"Three of the probes are on the nose for airspeed measurements—for the pilot, the co-pilot, and as a backup—and two are on the vertical stabilizer for the elevator feel-and-centering unit. If the airspeed difference between the pilot and co-pilot probes is greater than 5 kt. for 5 sec. consecutively, the pilots receive an “IAS (indicated airspeed) Disagree” alert. "

"A man with a watch knows what time it is. A man with two watches is never sure." (https://en.wikipedia.org/wiki/Segal's_law)
You can't take a concensus with two sensors.
So captain and co-pilot are lost as to the airplane's true speed but the backup sensor does nothing?
The aux pilot tube is for the ISFD, the backup flight instrument that's self-contained, including internal backup-power in the event the cockpit goes dark. So that's a third airspeed report available to the pilots.

I suspect we'll find the cause of the crash is something else entirely. They will find the black boxes, so we will know eventually.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on October 30, 2018, 04:42:11 am
For those interested in this stuff I highly recommend the book QF32
The captain takes you blow by blow through what it's like to get multiple conflicting warnings and whatnot

https://www.amazon.com.au/QF32-author-Life-Lessons-Cockpit-ebook/dp/B007KTLQ5W (https://www.amazon.com.au/QF32-author-Life-Lessons-Cockpit-ebook/dp/B007KTLQ5W)

Worth watching the episode of "Mayday" about QFA32 too.
 
https://www.youtube.com/watch?v=1eSiEFDBtvg (https://www.youtube.com/watch?v=1eSiEFDBtvg)

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on October 30, 2018, 04:59:03 am
There's so many pitot tube incidents.
Yep, especially when the pilots and ground crew on their pre-flight walk arounds can't/don't/won't see the socks placed on them to keep the various mason wasps from building nests in them.
Not all parts of the world have this problem but it's bad enough in some locations that covering the pitot tubes is mandatory but easily overlooked in pre-flight checks.  ::)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on October 30, 2018, 05:08:02 am
... or roll back to GPS for speed, or just stop issuing a fake airspeed if you know the sensors have failed and can't make a concensus.
GPS shows ground speed, not air speed. Not entirely useless, but they're usually not the same number.

I'm no pilot, but I would suggest GPS speed determination would be pretty much useless unless you know the direction and speed of the winds in your location at your flight level.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: NiHaoMike on October 30, 2018, 05:09:13 am
Yep, especially when the pilots and ground crew on their pre-flight walk arounds can't/don't/won't see the socks placed on them to keep the various mason wasps from building nests in them.
Not all parts of the world have this problem but it's bad enough in some locations that covering the pitot tubes is mandatory but easily overlooked in pre-flight checks.  ::)
They should make the covers striped fluorescent pink/orange/glow in the dark green balls that are hard to miss, and designed to tear away at typical flight speeds should one be forgotten.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on October 30, 2018, 06:07:45 am
Yep, especially when the pilots and ground crew on their pre-flight walk arounds can't/don't/won't see the socks placed on them to keep the various mason wasps from building nests in them.
Not all parts of the world have this problem but it's bad enough in some locations that covering the pitot tubes is mandatory but easily overlooked in pre-flight checks.  ::)
They should make the covers striped fluorescent pink/orange/glow in the dark green balls that are hard to miss, and designed to tear away at typical flight speeds should one be forgotten.
Well they do have ribbons on them but apparently that isn't always enough.

(https://www.aircraftspruce.com/cache/370-320-/catalog/graphics/1/13-02738.jpg)

https://www.aircraftspruce.com/menus/fb/covers_pitot.html (https://www.aircraftspruce.com/menus/fb/covers_pitot.html)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on October 30, 2018, 06:17:32 am
Yep anything that must be removed before flight is tagged bright red. This includes inside the cockpit (Small lanes often physically lock the controls so prevent the wind banging the directly connected control surfaces around)

And there have been cases where a pressure sensing port on the side of a plane was covered up with tape to protect it while the plane was washed. But then someone forgot to remove it and nobody noticed it so it caused all sorts of strange readings on the instruments once the plane has taken off.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on October 30, 2018, 07:19:03 am
... or roll back to GPS for speed, or just stop issuing a fake airspeed if you know the sensors have failed and can't make a concensus.
GPS shows ground speed, not air speed. Not entirely useless, but they're usually not the same number.

I'm no pilot, but I would suggest GPS speed determination would be pretty much useless unless you know the direction and speed of the winds in your location at your flight level.

That was my point. On the other hand, often one does have at least a ballpark idea of that information, especially when it comes time to land the plane. And ground speed remains useful for navigation purposes.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: station240 on October 30, 2018, 04:51:30 pm
Something really has gone wrong with this flight soon after take off.

Data from https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/ (https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/)

Graph of entire flight altitude/rate of climb
(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=559546;image)

Graph of takeoff altitude/rate of climb
(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=559552;image)
Flight is not a smooth climb to flight level, altitude and rate of climb are all over the place.
Indicates flight being flown manually.

Graph of last minute of flight altitude/rate of climb
(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=559558;image)
This is at what appears on radar maps (and radio comms) to be at the point where the plane was to turn around to return to the airport.
-33,000 ft/minute, no chance of survival.
I think the altitude values don't show the true horror of what occurred
My guess is the plane in fact attempted the turn while descending rapidly, this caused it to roll over and become impossible to recover from.

Various theories about causes, we can rule out engine problems, as planes with no working engines can still fly to some extent.
That just leaves:
A) pilot actions (combined with faulty instrumentation).
B) flight control malfunction or mechanical failure.
A is looking very likely, but B could also be involved or the main cause.

The crash people should be looking at is Air France Flight 447, where inconsistencies between the airspeed measurements were involved.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: edy on October 30, 2018, 05:20:41 pm
I'm not a pilot and have only rudimentary knowledge about this. Hopefully not too much of a noob question.... but if a Pitot tube or aircraft speed sensor was blocked or malfunctioning, it would tell the pilot the aircraft is going too slow? So wouldn't they speed up the airplane? Wouldn't speeding up help keep it flying in the air? I would imagine the reverse would be worse, where the sensor is telling you that you are going fast and you slow down and stall.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: station240 on October 30, 2018, 05:56:05 pm
I'm not a pilot and have only rudimentary knowledge about this. Hopefully not too much of a noob question.... but if a Pitot tube or aircraft speed sensor was blocked or malfunctioning, it would tell the pilot the aircraft is going too slow? So wouldn't they speed up the airplane? Wouldn't speeding up help keep it flying in the air? I would imagine the reverse would be worse, where the sensor is telling you that you are going fast and you slow down and stall.

The sensors give erratic readings, if one is bad you have to figure out which one it is. They work on air pressure within the sensor tube, the tube could be partially blocked, slow to respond etc.
Lets say there is an unwanted item (dead bug) inside the pitot tube, and it's rolling around inside. Changes in angle/altitude of the plane will give all sorts of crazy readings.
If you have more than one sensor malfunction, it becomes a very tricky task.

Planes fly within an envelope where too fast or too slow results in it falling out of the sky, or at least trying to.
Faster = more lift, climbing too fast results in reduced airspeed, which then results in almost no lift (a stall)
Slower = less lift, descending too slow results in increased airspeed, decreased lift, which then results in inability to climb back up.

If you don't trust the instruments, there are procedures to fly just with particular throttle and stick positions. There is a whole table to look at.

In other words, fly the plane carefully, ask the tower for altitude information on your plane, don't use instruments if you don't believe them.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: janoc on October 30, 2018, 06:02:03 pm
If you are interested how it works when there is an unreliable airspeed situation, here is an explanation from an actual 737 captain:

https://youtu.be/xiB1eejdgdQ?t=489

Basically annoying but, if correctly handled, a non-event. He explains that they even have tables that allow him to fly the plane without any airspeed indicator at all, only using known combination of pitch and power to achieve certain airspeeds (e.g. for landing). Furthermore, most of the procedures for this are memory items (i.e. something the pilot needs to know from memory, without having to rely on a checklist).

So should this happen the pilot flying is supposed to fly pitch and power, wings level. The crew cross-checks the instruments, see that two sets (e.g. backup + first officer's) agree and the third set (captain's) is wrong, the captain hands control over to the first officer and problem solved - exactly what happened on the flight the day before the crash.

And even if all three sets go out there is no reason for the plane to go down unless there is some other problem. Of course, that requires some hand-flying skills because autopilot is of no use in such situation. E.g. there has been an Airbus A330 in Brisbane that took off with the pitot covers still in place. The crew declared emergency and safely returned back to the airport.

I'm not a pilot and have only rudimentary knowledge about this. Hopefully not too much of a noob question.... but if a Pitot tube or aircraft speed sensor was blocked or malfunctioning, it would tell the pilot the aircraft is going too slow? So wouldn't they speed up the airplane? Wouldn't speeding up help keep it flying in the air? I would imagine the reverse would be worse, where the sensor is telling you that you are going fast and you slow down and stall.

When a pitot malfunctions, it could indicate basically anything. Pitot works by comparing the pressure of the oncoming air with pressure from a static port (usually at the bottom of the plane, not facing the airstream) and the airspeed indication is derived from that.

So if e.g. the pitot tube gets clogged you may not get any airspeed data at all (e.g. because someone forgot to remove the covers!), the data between the different tubes could be different (airliners have usually at least 3 pitots - one for captain and one for the first officer + one for the backup instruments), you may get lower than usual speeds if the tube is clogged partially.

Then you can have problems with the static port too. That is much more insidious because that causes a cascade of failures in the cockpit and it is not always immediately apparent what the problem is - you will lose airspeed indication, altimeters will go haywire, also vertical speed indication. Basically anything that depends on atmospheric pressure. There have been several accidents caused by clogged/covered static ports too.

That was my point. On the other hand, often one does have at least a ballpark idea of that information, especially when it comes time to land the plane. And ground speed remains useful for navigation purposes.

You have the ground speed available. However, ground speed is of little use for actually flying the plane - your lift (and thus the ability to stay aloft and not make a smoking crater on the ground) depends on the airspeed (the speed of the plane relative to the air) and not on ground speed.

Worse, the difference between indicated airspeed and ground speed grows the higher you are (and the lower the air pressure is) and also with any wind - if you have ever seen a plane land into a strong headwind by dropping down almost vertically on the runway with little forward movement that is why. The ground speed was low but the airspeed was still sufficient to maintain lift and to not stall (and crash) thanks to the headwind. Also the opposite has happened - e.g. if a plane encounters a strong windshear it could lose enough airspeed that it would stall and crash despite moving fast relative to the ground.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Jr460 on October 30, 2018, 06:08:02 pm
I'm not a pilot and have only rudimentary knowledge about this. Hopefully not too much of a noob question.... but if a Pitot tube or aircraft speed sensor was blocked or malfunctioning, it would tell the pilot the aircraft is going too slow? So wouldn't they speed up the airplane? Wouldn't speeding up help keep it flying in the air? I would imagine the reverse would be worse, where the sensor is telling you that you are going fast and you slow down and stall.

Simple.  You need two things for Indicated Air Speed, IAS, the ram air dynamic pressure and the static air pressure.   Block one or the other and changes in altitude will change your IAS.

Depending on the plane the Pitot tube might have the static port as part of the same structure, in other cases it is a flat hole on the side of the plane.


Had my static port freeze over once in the clouds when I picked up a tad of ice.   The Pitot heat had been one for the past hour or more.   I pulled a tad of power and started down as I called ATC and told them what I was doing.   I only needed about 1000 feet to get into above freezing air.  The ice broke loose and the airspeed and altimeter quickly snapped into place.  Done a bit more and broke out o the clouds into snow.  I knew what MEA and the ceiling so I knew I could breaking to VMC safely.  2 hours after getting the ice, landing in 50F weather and still had ice stuck to wingtip nav lights.   It comes on quick and stays put.

One other time, and we had a cover on the Pitot tube while parked, took the plane out, run up, takeoff, altimeter is not right, slow moving, doing odd things.   Nice VFR day, just came right around the pattern and landed based on eyes and feel of the plane.  Long story short, a spider had partly blocked way up into the static port with eggs.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: edy on October 30, 2018, 07:55:53 pm
Thanks for the explanations. I assumed like most smaller/simpler airplanes of the past you would just fly based on feel and feedback and what you saw, but that could be difficult at night or bad weather conditions (when you need to rely more on instruments). I guess it is very hard to tell how fast you are going or whether you are going up or dropping when you are far up from the ground. With enough experience in a particular aircraft you would have an intuitive sense of what kind of pitch and engine throttle is needed and when you are low to the ground you may be able to see if it is doing what you want the airplane to do.

With this particular new airplane, with fly-by-wire systems and computers automating a lot of the conditions (and perhaps, if I am to assume correctly, over-riding perhaps pilots in certain situations?) then could this be a case of AI or "smart algorithms" gone wrong? Or are pilots pretty much in control. I know it is too early to assume anything, we still don't know.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on October 30, 2018, 08:13:13 pm
On a slight side note, it takes next to nothing to receive ADS-B transmissions.  I have a Raspberry Pi + $12 USB Software Defined Radio in my garage uploading data to Flightradar24 (and by being a source node, you get full business level access to fr24)


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kleinstein on October 30, 2018, 08:52:48 pm
As the a not working pitot tube seems to be a rather common problem, the pilots should have regularly seen such a scenario in the simulator during training.

If the standard procedure is as simple as flying by setting power and other settings to a standard value depending on altitude, weight and whatever, I would even expect the auto-pilot to be able to do such a simple calculation / look in the table. At least for the first few seconds to minutes I would prefer this over a sudden turn over to manual control.


Still a lot of speculations to what causes the accident - just wait a few more days to get more info.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Jr460 on October 30, 2018, 08:58:30 pm
Thanks for the explanations. I assumed like most smaller/simpler airplanes of the past you would just fly based on feel and feedback and what you saw, but that could be difficult at night or bad weather conditions (when you need to rely more on instruments). I guess it is very hard to tell how fast you are going or whether you are going up or dropping when you are far up from the ground. With enough experience in a particular aircraft you would have an intuitive sense of what kind of pitch and engine throttle is needed and when you are low to the ground you may be able to see if it is doing what you want the airplane to do.

Even low to the ground your sense of airspeed is way off.   The problem is we see ground speed.   Other factors to into play, for example at night for some reason venting on the ground seems to be going by much faster.   But the biggest is that the plane and the wings perform based on IAS, Indicated airspeed, you then have TAS, true airspeed which corrects for air density, and then from that winds give you ground speed.  Now estimate IAS to better that +/- 5 knots based on all of that.   And even 5 knots fast or slow is not good.

That said, yes once you get good in a model and have been in and out of the same airport a lot, you know I need X power to hold altitude right at the top of the white arc with one notch of flaps.  Drop the gear abeam the numbers and touch nothing else, add flaps as you come base and then final.  In a PA28-200R that put me setup great for final.

I got a chance to try it by "feel" with a complete electrical failure at night, couldn't see any instruments, no time to reach and grab my flashlight.  I was already entering the pattern, just did what I always did hundreds of times.  Ended up down with no problems, I suspect maybe was  a tad slow.  I will say the pucker factor was very high.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on October 30, 2018, 09:03:20 pm
Looking at Air France flight 447:
"The loss of airspeed indications caused the autopilot, flight director, and autothrust to disconnect, as they require airspeed information to operate. The airplane’s handling characteristics also changed, as the airplane’s fly-by-wire flight controls degraded from its Normal to Alternate law. This led to the loss of many automatic protection mechanisms built into Normal law, including stall protection."
https://risk-engineering.org/concept/AF447-Rio-Paris (https://risk-engineering.org/concept/AF447-Rio-Paris)

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on October 30, 2018, 09:11:21 pm
Looking at Air France flight 447:
"The loss of airspeed indications caused the autopilot, flight director, and autothrust to disconnect, as they require airspeed information to operate. The airplane’s handling characteristics also changed, as the airplane’s fly-by-wire flight controls degraded from its Normal to Alternate law. This led to the loss of many automatic protection mechanisms built into Normal law, including stall protection."
https://risk-engineering.org/concept/AF447-Rio-Paris (https://risk-engineering.org/concept/AF447-Rio-Paris)
Yep.
Adding to this, if you then only have ground speed (GPS) to work with and a 100kt tailwind things won't end well.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rx8pilot on October 30, 2018, 09:32:41 pm
Yep.
Adding to this, if you then only have ground speed (GPS) to work with and a 100kt tailwind things won't end well.

Pitch + Power = Performance.
Any pilot can get rather close to a target airspeed with a known pitch+power (adjusted for altitude and temp).

The real trick is to understand that the system is in a state of failure and stop flying the airplane based on the potentially erroneous information. Identifying that a problem exists can easily be more challenging than dealing with it.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on October 30, 2018, 09:59:47 pm
I hope the black boxes survived.
I know they are tough, but it's not unlimited tough, and this was about as fast an impact as you can get. And the water is only approx 30m deep, so it might as well have just hit the ground.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on October 30, 2018, 10:02:41 pm
I hope the black boxes survived.
I know they are tough, but it's not unlimited tough, and this was about as fast an impact as you can get. And the water is only approx 30m deep, so it might as well have just hit the ground.
At the relevant impact speed, water is pretty damned hard. I doubt that the aircraft impacted the bottom with any kind of significant speed (meaning 30m, 100m, and 500m would be essentially "the same" wrt impact forces).

From another aviation forum that I waste spend a lot of time, aircraft might have impacted ~475 knots TAS and 40° nose down.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: alsetalokin4017 on October 30, 2018, 10:15:15 pm
This thread reminds me of when pilots start discussing electrical engineering on PPRuNe. 

This tragic loss of life MAY have been caused by faulty instrument indications which in turn caused the pilots to act inappropriately in some way. Maybe. They clearly struggled with the aircraft for many minutes before finally losing control and diving into the sea at very high speed.

"Unreliable airspeed" is something that airline pilots are supposed to be practicing in simulators regularly. Pitch and power settings to establish a gentle climb at a reasonable airspeed despite faulty indications are supposed to be embedded in the pilot's memory and trained regularly in sim. This flight was in daylight, good visibility and good weather, so nothing at all like AF447. The 737 MAX has mechanical primary flight controls, it is not totally "fly by wire" like Airbus.

Faulty instrument indications could be caused by many things, all of which would have the same outcome, supposedly manageable safely by the crew if they had time, and it appears this crew did have time but didn't manage safely. The case of the B2 at Guam that had the blocked pitot system on takeoff did not allow the pilots enough time to do anything but eject; it was out of control from the moment of liftoff.


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on October 30, 2018, 10:31:24 pm
I hope the black boxes survived.
I know they are tough, but it's not unlimited tough, and this was about as fast an impact as you can get. And the water is only approx 30m deep, so it might as well have just hit the ground.
At the relevant impact speed, water is pretty damned hard.

Yep, I have experience drop testing stuff onto water, it can be as hard as a rock. But it has a lot to do with how surface areas impact etc.

Quote
I doubt that the aircraft impacted the bottom with any kind of significant speed (meaning 30m, 100m, and 500m would be essentially "the same" wrt impact forces).
From another aviation forum that I waste spend a lot of time, aircraft might have impacted ~475 knots TAS and 40° nose down.

Possibly. If it was very nose down, then the bottom would have impacted in some way I suspect. But at 40deg that kinda flat-ish in the scheme of thing, so may not have hit bottom in that case.
In any case, it they haven't located the black box by now (which have transponders), then it's likely they are damaged. Although it's also possible the transponder could have sheered off the recorder housing, so they may not be together.
They are located in the tail, so hopefully are just sitting on the bottom somehow instead of buried in the sand.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on October 30, 2018, 10:59:53 pm
For those interested in this stuff I highly recommend the book QF32
The captain takes you blow by blow through what it's like to get multiple conflicting warnings and whatnot

https://www.amazon.com.au/QF32-author-Life-Lessons-Cockpit-ebook/dp/B007KTLQ5W (https://www.amazon.com.au/QF32-author-Life-Lessons-Cockpit-ebook/dp/B007KTLQ5W)

Better up the ATSB report is like a Agatha Christie multiplied by the Lord of the rings! Hairy, quite close to total death!
Many detailed pictures.
http://www.atsb.gov.au/publications/investigation_reports/2010/aair/ao-2010-089.aspx (http://www.atsb.gov.au/publications/investigation_reports/2010/aair/ao-2010-089.aspx)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Lord of nothing on October 30, 2018, 11:03:23 pm
Quote
I have a Raspberry Pi + $12 USB Software Defined Radio in my garage
o you share? I use a proper Equipment for.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on October 30, 2018, 11:04:53 pm
Quote
I have a Raspberry Pi + $12 USB Software Defined Radio in my garage
o you share? I use a proper Equipment for.

I wouldn't mind setting up a receiver, but i can't find a map of existing installations?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: edy on October 31, 2018, 05:37:14 am
Not to derail the main thread, but I just noticed this article on CNN and thought :wtf::

https://www.cnn.com/travel/article/electric-easyjet-planes-intl/index.html (https://www.cnn.com/travel/article/electric-easyjet-planes-intl/index.html)

I think it is mostly a marketing strategy the company concocted to get more media coverage, but I am concerned about the 10-15 years timeline they expect these to be viable, tested and practical. I know they have small airplanes on short routes already in operation but is it something that paying passengers are willing to risk? If an electric car fails vs. electric plane, your chances of surviving may vary quite a bit.

We are just on the heels of this 737 tragedy which is a brand new plane, but I don't know the history of electric planes well enough to say if they are as reliable and safe at this point. From a small Cessna-style 2 seater to 9 seater electric with maybe 500km range (short flights) seem to be already on the near horizon, but I can't imagine yet seeing anything like the picture below without a major breakthrough:

(https://dynaimage.cdn.cnn.com/cnn/q_auto,w_1351,c_fill,g_auto,h_760,ar_16:9/http%3A%2F%2Fcdn.cnn.com%2Fcnnnext%2Fdam%2Fassets%2F181030130218-easyjet-wright-electric.jpg)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Lord of nothing on October 31, 2018, 09:41:22 am
Quote
I wouldn't mind setting up a receiver, but i can't find a map of existing installations?
depend on the national law you could end in Jail for but on the other end there are so many People go get them all is impossible.
There arent any Maps because you must/ can/ have to share from IP to IP.
Its like a Black Marked Business you need to know someone to get he Data.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: nfmax on October 31, 2018, 09:55:44 am
Of course, the previous day's problems may have had nothing at all to do with the cause of the accident. It is also possible that knowledge of the previous failure may have misled the aircrew into inappropriate response to the actual failure, whatever that may turn out to be. There is a term for this, I can't remember - getting locked into a wrong interpretation of the situation causing you to disregard evidence (that you are interpreting wrongly).
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: janoc on October 31, 2018, 10:38:17 am
With this particular new airplane, with fly-by-wire systems and computers automating a lot of the conditions (and perhaps, if I am to assume correctly, over-riding perhaps pilots in certain situations?) then could this be a case of AI or "smart algorithms" gone wrong? Or are pilots pretty much in control. I know it is too early to assume anything, we still don't know.

737 is not a fly-by-wire, it has classic flight controls (hydraulics for the most part).

There is also no "AI" or "smart algorithms" overriding the pilots, not even on the Airbuses. The electronics is designed in a way that whenever something seems out of whack, the automation will warn the crew and disconnect, handing the entire mess to the human sitting there to sort out.

What some planes (Airbus, not the crashed 737) have are things like the "alpha floor" protections (it prevents stalling under certain conditions) but these are typically the first ones lost/disabled when the computers detect some kind of anomaly - that's what Airbus refers to as "laws" (normal vs alternate when something is wrong for ex).

And when the pilot feels the automation is doing something it shouldn't for whatever reason, there is a disconnect button on the yoke/sidestick and for the worst case there is always a circuit breaker that can be pulled. Even on the Airbus you can fly the plane without the computers - it is going to be difficult but it is still possible.

Looking at Air France flight 447:
"The loss of airspeed indications caused the autopilot, flight director, and autothrust to disconnect, as they require airspeed information to operate. The airplane’s handling characteristics also changed, as the airplane’s fly-by-wire flight controls degraded from its Normal to Alternate law. This led to the loss of many automatic protection mechanisms built into Normal law, including stall protection."
https://risk-engineering.org/concept/AF447-Rio-Paris (https://risk-engineering.org/concept/AF447-Rio-Paris)


Guys, AF447 is not a comparable situation. AF447 was first and foremost caused by relatively inexperienced crew mishandling the controls in a major way - newer attempting the "pitch and power" stable configuration and causing the plane to stall by keeping pulling at the side stick almost all the way down. The crew has never recognized the stall and never attempted to correct it, despite the warnings and buffet they were feeling. It was also not clear who (if anyone) was actually flying - both crewmen were trying to make control inputs at the same time.

The plane was perfectly flyable the entire time, though. At the time of crash it was flown by two rather inexperienced first officers (captain went to sleep after the departure from Rio, I believe, as it was supposed to be a rather uneventful part of the trip). The failure has also occurred at night, at high altitude and in turbulence. None of that was the case for the Lion Air flight (experienced crew, daytime, low altitude, good weather).

Also, since then a lot of training since the AF447 has been focused on both manual flying and recovery from similar failures (the AF447 pilots except of the captain apparently didn't have any training of dealing with unreliable airspeed in a "manual" plane, both having been trained directly on the Airbus).

Here is the AF447 report:
https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf (https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf)

Given the (few) data we have about the Lion Air flight, it would surprise me if there was any similarity at all to the AF447 flight. The Lion Air crew was obviously not in a stall, they were trying to maintain level flight but ultimately failed.

This entire pitot discussion is very likely a red herring caused by the maintenance log from the day before and there had to be some other major mechanical problem on board  (uncontained engine failure, explosion, decompression, whatever) to cause a crash like this. This kind of speculation is pretty pointless until there is more data available, e.g. from the black boxes.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: amyk on October 31, 2018, 11:54:50 am
This entire pitot discussion is very likely a red herring caused by the maintenance log from the day before and there had to be some other major mechanical problem on board  (uncontained engine failure, explosion, decompression, whatever) to cause a crash like this. This kind of speculation is pretty pointless until there is more data available, e.g. from the black boxes.
Something like https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261 ?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: janoc on October 31, 2018, 03:47:38 pm
This entire pitot discussion is very likely a red herring caused by the maintenance log from the day before and there had to be some other major mechanical problem on board  (uncontained engine failure, explosion, decompression, whatever) to cause a crash like this. This kind of speculation is pretty pointless until there is more data available, e.g. from the black boxes.
Something like https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261 ?

Flight 261 was an MD83, not a 737, the rudder is driven in a different way. And given that this was a brand new plane, the chance that something has worn out already (in the 261 crash the rudder jackscrew threads were worn off due to poor maintenance) is minimal.

It could be literally anything at this point. Even something like losing the rudder fin or even an entire vertical stabilizer (happened in Japan before bcs of poorly repaired tailstrike - the plane flew for a while before hitting a mountain, also old models of 737,  not NG or MAX, had a history of rudder problems). Or an engine blowing up and taking out the hydraulics lines (Sioux City crash landing - landed using differential engine thrust and manual trim because main flight controls were inop). Or a bomb going off. Or even a fight in the cockpit for all we know. I am not saying that any of these are likely but until we know more it is a speculation equally good as any other.

Could it be that the crash was related to a poorly repaired failure from the day before and the crew stuffing it up? Sure. But it could have also been a completely different problem.

So far the only information are rather inaccurate Flightradar data, crew requesting a return to Jakarta (suggesting a mechanical problem on board) and the information that there has been an avionics failure the day before. Nothing else. Trying to conclude anything from only that is a fool's errand.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on October 31, 2018, 04:54:07 pm
Something like https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261 ?
Flight 261 was an MD83, not a 737, the rudder is driven in a different way. And given that this was a brand new plane, the chance that something has worn out already (in the 261 crash the rudder jackscrew threads were worn off due to poor maintenance) is minimal.
Alaska 261 was a horizontal stabilizer (controls pitch trim) jackscrew issue, not a rudder (controls yaw) defect.

That it is almost surely unrelated is 100% true (other than both flights ending in water with loss of all aboard).
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on October 31, 2018, 05:29:05 pm
There's so many pitot tube incidents.
Yep, especially when the pilots and ground crew on their pre-flight walk arounds can't/don't/won't see the socks placed on them to keep the various mason wasps from building nests in them.
Not all parts of the world have this problem but it's bad enough in some locations that covering the pitot tubes is mandatory but easily overlooked in pre-flight checks.  ::)

Worked Avionics Instruments in the USAF late 70's early 80's and we had a couple occasions where we needed to replace a pitot tube because the cover wasn't removed and burned up in-flight.  I don't know how that could be missed during takeoff roll as the IAS for that circuit would be AFU.  I kind of doubt this crash was due to a covered pitot tube as it should have been obvious pretty early.  OTH, the crash did happen shortly after takeoff.  The FDR and CVR should clear things up.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: janoc on October 31, 2018, 05:29:41 pm
Alaska 261 was a horizontal stabilizer (controls pitch trim) jackscrew issue, not a rudder (controls yaw) defect.

That it is almost surely unrelated is 100% true (other than both flights ending in water with loss of all aboard).

Ah right, not sure why I wrote "rudder". D'oh. Thanks for the correction.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on November 01, 2018, 04:01:07 am
Latest update from local news by the reporter that on the SAR ship, black box recovered today at 10 am local time, and apparently undamaged, and it was buried under the mud at about 30m from the surface.

The signals were detected at these coordinates S 05 48 48.051 - E 107 07 37.622 and S 05 48 46.545 - E 107 07 38.393.

(https://akcdn.detik.net.id/community/media/visual/2018/11/01/2ad1a972-6560-43a9-a3df-1ec6fedeecaa_169.jpeg?w=780&q=90)
(https://akcdn.detik.net.id/community/media/visual/2018/11/01/8e56e3f3-d424-46a9-bbd4-02729c4660e8_169.jpeg?w=780&q=90)



Transferred into proper & safe container.

(https://akcdn.detik.net.id/community/media/visual/2018/11/01/bb4341e0-dec4-49c6-b495-da4d6e57100e_169.jpeg?w=780&q=90)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on November 01, 2018, 05:30:06 am
Latest update from local news by the reporter that on the SAR ship, black box recovered today at 10 am local time, and apparently undamaged, and it was buried under the mud at about 30m from the surface.

I'm surprised the pinger worked under the mud, but then again, 30m of water makes it vastly easier
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: amyk on November 01, 2018, 12:15:35 pm
Something like https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261 ?
Flight 261 was an MD83, not a 737, the rudder is driven in a different way. And given that this was a brand new plane, the chance that something has worn out already (in the 261 crash the rudder jackscrew threads were worn off due to poor maintenance) is minimal.
Alaska 261 was a horizontal stabilizer (controls pitch trim) jackscrew issue, not a rudder (controls yaw) defect.

That it is almost surely unrelated is 100% true (other than both flights ending in water with loss of all aboard).
I meant related as in "sudden failure of control surface". The fact that the plane was so new means it could be a manufacturing defect.

Good they recovered the recorders, we should get the answer soon.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Homer J Simpson on November 01, 2018, 12:36:15 pm

Scanning the Wikipedia article on the 737 Max...........

https://en.wikipedia.org/wiki/Boeing_737_MAX

Seems to have been / is a lot of pressure to produce as many planes as possible.



"On August 13, 2015, the first 737 MAX fuselage completed assembly at Spirit Aerosystems in Wichita, Kansas, for a test aircraft that would eventually be delivered to launch customer Southwest Airlines.[26] On December 8, 2015, the first 737 MAX—a MAX 8 named "Spirit of Renton"—was rolled out at the Boeing Renton Factory.[27][28]

Because GKN could not produce the titanium honeycomb inner walls for the thrust reversers quickly enough, Boeing switched to a composite part produced by Spirit to deliver 47 MAXs per month in 2017. Spirit supplies 70 percent of the 737 airframe, including the fuselage, thrust reverser, engine pylons, nacelles, and wing leading edges.[29]

A new spar-assembly line with robotic drilling machines should increase throughput by 33 percent. The Electroimpact automated panel assembly line sped up the wing lower-skin assembly by 35 percent.[30] Boeing plans to increase its 737 MAX monthly production rate from 42 planes in 2017 to 57 planes by 2019.[31]

The rate increase strains the production and by August 2018, over 40 unfinished jets were parked in Renton, awaiting parts or engine installation, as CFM engines and Spirit fuselages were delivered late.[32] After parked airplanes peaked at 53 at the beginning of September, Boeing reduced this by nine the following month, as deliveries rose to 61 from 29 in July and 48 in August.[33] "



Interesting if it turns out to be related to manufacturing.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on November 01, 2018, 05:55:36 pm
The rate increase strains the production and by August 2018, over 40 unfinished jets were parked in Renton, awaiting parts or engine installation, as CFM engines and Spirit fuselages were delivered late.[32] After parked airplanes peaked at 53 at the beginning of September, Boeing reduced this by nine the following month, as deliveries rose to 61 from 29 in July and 48 in August.[33] "

Hard to imagine there's room for 40 unfinished jets at Renton, it's a pretty small airport.  There's 27 parked there (all over the airfield) in the Google Sat image; and they're spread out all over the place, not sure where you'd find the room to double that.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on November 01, 2018, 05:59:20 pm
I'm reading that it's the Flight Data Recorder (there are two 'black boxes' the FDR and the Cockpit Voice Recorder)..

In the past there have been issues with 737 rudders (https://en.wikipedia.org/wiki/Boeing_737_rudder_issues) , but that was completely redesigned  with the previous generation of the 73.  Until they start looking at what's on that recording, we really wont know.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 01, 2018, 06:20:25 pm
As a Avionics Instruments tech while working in the USAF back in the day the reports from a previous flight that also had a problem shortly after takeoff that cleared and they continued on there flight it's looking to me that rather than a cover on a pitot tube it looks like a fitting in the system maybe lose giving erratic readings but then stabilize later.  The pitot static system consists of two lines: the static line that monitor atmospheric pressure used for altitude and vertical velocity, and a ram pressure that's used for indicated airspeed and used in combination with the static pressure and temperature for TAS.  I suspect that the static line had a lose fitting and if that's true it's also possible a ram pressure line may also have been lose.

During maintenance of the pitot static system lines are opened to hook up test equipment to provide calibrated pressures to check the altimeters and airspeed indicators for correct readings.  Of course, when the tests are done the equipment is disconnected AND the lines must then be reconnected.  I've seen it happen where this is done but the fittings are not tightened -- they are snugged up but not immediately tightened so at some point down the road the back off a bit and...

The FDR should reveal this even of the pilots didn't properly identify it.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Wolfgang on November 02, 2018, 01:20:37 pm
one of the more trivial reasons for a Pitot failure is an insect stuck in the inlet.
The incoming air then never reaches the heater, icing could occur and the readings are nonsense.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 02, 2018, 06:20:09 pm
one of the more trivial reasons for a Pitot failure is an insect stuck in the inlet.
The incoming air then never reaches the heater, icing could occur and the readings are nonsense.


Yes, that's true, however the previous flight reported similar issues so you would THINK they would do an inspection of the pitot tubes before the next flight.

But, erratic readings could be explained by an inspect or other FOD in the pitot tube.

Again, this should be plainly obvious in the FDR data.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: IanMacdonald on November 02, 2018, 07:11:10 pm
I'm not a pilot and have only rudimentary knowledge about this. Hopefully not too much of a noob question.... but if a Pitot tube or aircraft speed sensor was blocked or malfunctioning, it would tell the pilot the aircraft is going too slow? So wouldn't they speed up the airplane? Wouldn't speeding up help keep it flying in the air? I would imagine the reverse would be worse, where the sensor is telling you that you are going fast and you slow down and stall.

No. The ASI measures the difference in pressure between the pitot and static vents. The pitot pressure would remain as it was before it was blocked, so the instrument would likely read the same regardless of a speed increase or decrease in level flight. Although as you gained altitude the indicated speed would increase due to the reducing pressure on the static side. That's maybe what happened, and lead to a stall.

In fact, for VMC flying anyway, most of the stuff on the instrument panel is eye candy. The one thing you really need is to know your airspeed, as it's hard to judge visually.  The rest you can tell with the Mk1 eyeball.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on November 02, 2018, 07:23:48 pm
Is there no sanity check built into the system for the airspeed indication (other than the duplicated pitots and instruments)?

I would have though that the system ought to be able to combine engine thrust, altitude, attitude, control surface settings, takeoff weight, fuel used etc. to calculate and generate an airspeed display plausibility warning. Maybe even to provide a emergency backup 'estimated' airspeed indication?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: cdev on November 02, 2018, 07:49:42 pm
One would think that after the accident over the Atlantic several years ago, that the pitot tube icing issue would have been solved by installing multiple redundant pitot tubes, as well as multiple redundant everything else. the same thing with the satellite data link. Every multimillion dollar aircraft that flies should have one tied to a pair of redundant GPS receivers, one at the nose and one near the tail. Using the two it should be possible to get the exact position and heading anywhere in the world of every one of those planes, in seconds. They get a very good quality of data simply from GPS of their airspeed. The pitot tubes might be good to have but they should all be looked at at the same time and if any of the readings is wildly divergent, it should be eliminated as such an outlier its almost certainly wrong.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 02, 2018, 07:53:59 pm
Is there no sanity check built into the system for the airspeed indication (other than the duplicated pitots and instruments)?

I would have though that the system ought to be able to combine engine thrust, altitude, attitude, control surface settings, takeoff weight, fuel used etc. to calculate and generate an airspeed display plausibility warning. Maybe even to provide a emergency backup 'estimated' airspeed indication?

Of course there is, and it's been well established in this thread already. If two completely independent systems don't agree on airspeed, the pilots are going to be alerted. If they follow their training, they'll go to pitch and power settings to ensure a proper airspeed, then they can reference the backup instrument for a third independent reading. If there's no consensus, they can fly pitch and power settings all the way to a safe landing.

If machines were good enough to be trusted to do the job all the time, there wouldn't be pilots on board at all.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 02, 2018, 07:57:18 pm
One would think that after the accident over the Atlantic several years ago, that the pitot tube icing issue would have been solved by installing multiple redundant pitot tubes, as well as multiple redundant everything else. the same thing with the satellite data link. Every multimillion dollar aircraft that flies should have one tied to a pair of redundant GPS receivers, one at the nose and one near the tail. Using the two it should be possible to get the exact position and heading anywhere in the world of every one of those planes, in seconds. They get a very good quality of data simply from GPS of their airspeed. The pitot tubes might be good to have but they should all be looked at at the same time and if any of the readings is wildly divergent, it should be eliminated as such an outlier its almost certainly wrong.

GPS doesn't give airspeed, it gives ground speed. Great for navigation, but very inaccurate as an airspeed replacement. Could differ by as much as 250mph if the plane is in a jet stream.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on November 02, 2018, 08:00:02 pm
One would think that after the accident over the Atlantic several years ago, that the pitot tube icing issue would have been solved by installing multiple redundant pitot tubes, as well as multiple redundant everything else. the same thing with the satellite data link. Every multimillion dollar aircraft that flies should have one tied to a pair of redundant GPS receivers, one at the nose and one near the tail. Using the two it should be possible to get the exact position and heading anywhere in the world of every one of those planes, in seconds. They get a very good quality of data simply from GPS of their airspeed. The pitot tubes might be good to have but they should all be looked at at the same time and if any of the readings is wildly divergent, it should be eliminated as such an outlier its almost certainly wrong.
GPS derived ground speed means shit for flying a plane, you need airspeed which can be influenced by prevailing winds that could be all over the place at different altitudes.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on November 02, 2018, 08:08:34 pm
Is there no sanity check built into the system for the airspeed indication (other than the duplicated pitots and instruments)?

I would have though that the system ought to be able to combine engine thrust, altitude, attitude, control surface settings, takeoff weight, fuel used etc. to calculate and generate an airspeed display plausibility warning. Maybe even to provide a emergency backup 'estimated' airspeed indication?

Of course there is, and it's been well established in this thread already. If two completely independent systems don't agree on airspeed, the pilots are going to be alerted. If they follow their training, they'll go to pitch and power settings to ensure a proper airspeed, then they can reference the backup instrument for a third independent reading. If there's no consensus, they can fly pitch and power settings all the way to a safe landing.

If machines were good enough to be trusted to do the job all the time, there wouldn't be pilots on board at all.

So there's a nice big indicator saying one or both of your airspeed indications may be implausible, without relying on the pilots constantly visually cross-checking their indicators?

Edit: Sorry, I missed the reference to a third, backup, instrument. Is that Pitot too?... and is it linked into the automatic comparison warning too?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: cdev on November 02, 2018, 09:11:07 pm
I bet!

 the speed of the gulf stream etc, adds a substantial boost/slow down to planes flying in it, you can see that happening when they change their heading in relation to it.
GPS derived ground speed means shit for flying a plane, you need airspeed which can be influenced by prevailing winds that could be all over the place at different altitudes.

Multiple, heated pitot tubes would be good, I wonder what other kinds of air speed sensors exist.

Anything mechanical that I can think of right now at least, besides a pitot pressure indicator would likely fail at a typical jets speed though.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Mr. Scram on November 02, 2018, 09:23:45 pm
Multiple, heated pitot tubes would be good, I wonder what other kinds of air speed sensors exist.

Anything mechanical that I can think of right now at least, besides a pitot pressure indicator would likely fail at a typical jets speed though.
Mechanical measures aren't completely infeasible. A small propeller device is deployed when all engines and the APU fail to power the bare essentials. This device is obviously capable of dealing with fairly substantial forces, even though a gliding jet liner will be slower than at cruising speeds.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Wolfgang on November 02, 2018, 09:24:09 pm
I bet!

 the speed of the gulf stream etc, adds a substantial boost/slow down to planes flying in it, you can see that happening when they change their heading in relation to it.
GPS derived ground speed means shit for flying a plane, you need airspeed which can be influenced by prevailing winds that could be all over the place at different altitudes.

Multiple, heated pitot tubes would be good, I wonder what other kinds of air speed sensors exist.

Anything mechanical that I can think of right now at least, besides a pitot pressure indicator would likely fail at a typical jets speed though.

When I took my flying lessons (AS350B3) the procedure for a suspect Pitot was to fly a circle and to look at the difference of TAS and ground speed.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: khs on November 02, 2018, 10:13:44 pm
here a link to an Austrian website (English) discussing crashes & accidents..

http://avherald.com/h?article=4bf90724&opt=0 (http://avherald.com/h?article=4bf90724&opt=0)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 02, 2018, 10:26:19 pm
When I took my flying lessons (AS350B3) the procedure for a suspect Pitot was to fly a circle and to look at the difference of TAS and ground speed.

Perfectly reasonable for a helicopter, for which low airspeed by itself typically isn't an emergency. Maneuvers that cause low rotor speeds/blade stall are the real killers, as I understand it. Not that I've had any rotor training.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Wolfgang on November 02, 2018, 10:37:13 pm
When I took my flying lessons (AS350B3) the procedure for a suspect Pitot was to fly a circle and to look at the difference of TAS and ground speed.

Perfectly reasonable for a helicopter, for which low airspeed by itself typically isn't an emergency. Maneuvers that cause low rotor speeds/blade stall are the real killers, as I understand it. Not that I've had any rotor training.

You would run this maneuvre at a medium power setting (80% MCP) and a level flight, and try a 2 minutes turn. Bank angle should be very moderate then.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on November 03, 2018, 08:33:20 am
Quote
Lion Air sent engineer on board fatal flight as ‘anticipatory measure’
https://thewest.com.au/news/aviation/lion-air-sent-engineer-on-board-fatal-flight-in-anticipatory-measure-ng-b881011084z
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on November 03, 2018, 08:36:57 am
Surprised at how intact the black box is, pinger still attached:

(https://cdn.newsapi.com.au/image/v1/76f362b38beebd6b3e7b79540873d024?width=1024)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on November 03, 2018, 08:52:17 am
Then again the black box is a solid metal block. Crashes on land are probably harder for it, especially if the impact is something like straight into a mountain, topped off with the fuel catching fire.

Also why are they called black boxes if they are never actually painted black?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 03, 2018, 05:33:19 pm
Press is saying the flight data recorder is damaged or needs parts for repair or it was found in deep water. Load of bollocks.

A few professionals speculating the airplane was going around 600MPH at impact, explaining why it basically shattered into pieces. This is using the FlightData numbers and it would have to be nose down with engine power to get that fast.

old Boeing article: (http://www.boeing.com/commercial/aeromagazine/aero_02/textonly/s01txt.html)
"Beginning in 1965, FDRs (commonly known as "black boxes") were required to be painted bright orange or bright yellow, making them easier to locate at a crash site. "

15GB for a 787 flight, 1,675 sensors 0.2-20Hz. (https://conf.slac.stanford.edu/xldb2018/sites/xldb2018.conf.slac.stanford.edu/files/Tues_15.50%20Ian%20Willson%20XLDB%202018%20Boeing%20IOT.pdf)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 03, 2018, 05:53:47 pm
If they were going 600mph at impact something else has to be going on -- they never got that high so unless they did a powered dive at high angle it's hard to see how they could have been going that fast.  At this point I'm beginning to wonder if maybe the CVR won't be more telling.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: amyk on November 03, 2018, 06:27:28 pm
The FDR is still very intact because it would've had the whole length of the plane to decelerate (probably while punching through materials softer than it) as it hit the water, so the G forces it experienced weren't that high.

On the other hand, everything in the nose is probably crushed beyond recognition.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Lord of nothing on November 03, 2018, 07:11:38 pm
Quote
600mph
a What?!  :palm:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 03, 2018, 08:37:41 pm
Knots (https://en.wikipedia.org/wiki/Knot_(unit)) are not SI and not far from MPH as a layman's comparison I guess. American aerospace people were doing the speed numbers.

OK FDR is totally ripped off the base with power supply and I/O, all they pulled is the 'crash survivable memory unit' out of the water?
That seems very strange to have all the metal nicely ripped off, leaving a more or less handheld FDR for press pictures. Those divers must use tin snips  :o
Lion Air possibly chose the L3 tech FDR FA2100.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SeanB on November 03, 2018, 09:53:46 pm
It ripped off the base sheet, probably part of the design to reduce the impact on the inner memory stack. That it is all nice and intact with the pinger is not a surprise, it is designed to do that.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 03, 2018, 10:18:36 pm
If they were going 600mph at impact something else has to be going on --

33,000 ft/min = 167 meters/second = 600 kilometers/hour = 375 miles/hour. Someone got their numbers and units mixed up.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: cdev on November 03, 2018, 10:39:13 pm
Did the accident happen during a storm or unusual weather of any kind?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Mr. Scram on November 03, 2018, 10:41:57 pm
Did the accident happen during a storm or unusual weather of any kind?
It's on the first page somewhere near the top.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 03, 2018, 10:59:38 pm
If they were going 600mph at impact something else has to be going on --

33,000 ft/min = 167 meters/second = 600 kilometers/hour = 375 miles/hour. Someone got their numbers and units mixed up.
I believe it was 31K fpm vertical velocity and something like 360 knots of ground speed (horizontal velocity).
Solves to something around 475 knots (about 550 mph) 40° below horizontal.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 03, 2018, 11:21:15 pm
Kill me for starting with Bloomberg numbers (https://www.bloomberg.com/news/articles/2018-11-03/lion-air-jet-s-final-plunge-may-have-reached-600-miles-per-hour) supposedly backed up by:
Expert 1: "Scott Dunham, a former National Transportation Safety Board investigator, who combined the distance the plane traveled horizontally and vertically to arrive at a speed estimate." {600mph}
Expert 2: "John Hansman, a Massachusetts Institute of Technology aeronautics and astronautics professor, estimated the plane was flying at 540mph in the final moments..."
Expert 3: Jasenka Rakas, a lecturer in engineering and aviation at the University of California at Berkeley "...the speed could have been between 586 and 633 mph."
added Bloomberg hype? "At the end, it fell 1,025ft in 1.6 seconds."

I thought the ~600mph was vector sum of vertical and horizontal velocities.

Flightradar24 data (https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/) looking at timestamps, it was at 28,000ft and took minutes to drop, so -33,000ft/min seems wrong too.
2018-10-28 23:31:56Z.030 last two samples do say it fell 1,025ft in 1.6 seconds.

edit: confused flight JT610 with JT43.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SiliconWizard on November 04, 2018, 02:50:18 am
Quote
600mph
a What?!  :palm:

Almost breaking the sound barrier! :-DD
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 04, 2018, 02:56:13 am
Flightradar24 data (https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/) looking at timestamps, it was at 28,000ft and took minutes to drop, so -33,000ft/min seems wrong too.
You're confusing the data for the prior flight with that of the fatal flight. On it's last flight, it never got much over 6000 ft.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 04, 2018, 04:49:32 am
Flightradar24 data (https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/) looking at timestamps, it was at 28,000ft and took minutes to drop, so -33,000ft/min seems wrong too.
You're confusing the data for the prior flight with that of the fatal flight. On it's last flight, it never got much over 6000 ft.
Fixed, it is 1,025ft in 1.6 seconds at the end.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Lord of nothing on November 04, 2018, 06:55:54 am
Why not put some SD Cards across the Aircraft when the Crash the have some additional infos when the get found.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: donotdespisethesnake on November 04, 2018, 07:22:47 am
Kill me for starting with Bloomberg numbers (https://www.bloomberg.com/news/articles/2018-11-03/lion-air-jet-s-final-plunge-may-have-reached-600-miles-per-hour) supposedly backed up by:
Expert 1: "Scott Dunham, a former National Transportation Safety Board investigator, who combined the distance the plane traveled horizontally and vertically to arrive at a speed estimate." {600mph}
Expert 2: "John Hansman, a Massachusetts Institute of Technology aeronautics and astronautics professor, estimated the plane was flying at 540mph in the final moments..."
Expert 3: Jasenka Rakas, a lecturer in engineering and aviation at the University of California at Berkeley "...the speed could have been between 586 and 633 mph."
added Bloomberg hype? "At the end, it fell 1,025ft in 1.6 seconds."

Ah yes, Bloomberg, the well known purveyor of fake news. I wouldn't trust them to tell me the right time.   :palm:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: imo on November 04, 2018, 10:55:46 am
480mph
https://www.youtube.com/watch?v=zPe-bKIid8w (https://www.youtube.com/watch?v=zPe-bKIid8w)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on November 05, 2018, 07:44:50 pm
Apparently the plane had airspeed indicator problems on its final FOUR flights! Surely enough opportunities for someone to check the pitot tubes and do some sort of investigation?  :-\

https://www.bbc.co.uk/news/world-asia-46094495 (https://www.bbc.co.uk/news/world-asia-46094495)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on November 05, 2018, 08:11:01 pm
Well they do have ribbons on them but apparently that isn't always enough.
Why not some kind of lockout/tagout system then? Put a code in the box which requires keys from all the tags to open (or a bolt cutter for eventualities) and which needs to be transmitted to the pilot.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on November 05, 2018, 08:21:54 pm
Well they do have ribbons on them but apparently that isn't always enough.
Why not some kind of lockout/tagout system then? Put a code in the box which requires keys from all the tags to open (or a bolt cutter for eventualities) and which needs to be transmitted to the pilot.
Yes it certainly wouldn't be hard to add some sort of fail-safe system so that pilots had live info on their displays on the status of pitot condoms.
Even near proximity RFID tags linked to the flight systems so the aircraft couldn't taxi under its own power would eliminate all stuff ups.

Ain't hard, only the willingness to do so is.  :palm:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: glarsson on November 05, 2018, 08:31:12 pm
Even near proximity RFID tags linked to the flight systems so the aircraft couldn't taxi under its own power would eliminate all stuff ups.

Ain't hard, only the willingness to do so is.  :palm:
Not so easy. The manufacturer has to certify that this mechanism will not be a hazard, e.g. will never disable the aircraft during normal operation.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on November 05, 2018, 08:37:51 pm
Even near proximity RFID tags linked to the flight systems so the aircraft couldn't taxi under its own power would eliminate all stuff ups.

Ain't hard, only the willingness to do so is.  :palm:
Not so easy. The manufacturer has to certify that this mechanism will not be a hazard, e.g. will never disable the aircraft during normal operation.
Yer what ? ? ?
No different to any other sensor or system code in the modern aircraft !

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: glarsson on November 05, 2018, 09:14:12 pm
They are also not easy, but a device that can disable the aircraft (even designed to do it) is something else. Can you guarantee that these RFID sensors can't fail and disable the aircraft during takeoff, cruise or landing?
What is worse; a failed pitot tube or one sensor that disables the aircraft?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 05, 2018, 09:37:19 pm
Aircraft manufacturers have probably figured pitot safety out better than random EE enthusiasts brainstorming here.
There's an airspeed alive callout and an 80-knot cross-check to catch gross pitot errors. It's extremely unlikely that this airplane took off with pitot covers installed (if that's the case, RFID tagged covers are a non-solution).

They have the FDR; they can hear roughly where the CVR is and are likely to recover it. That will tell a lot more than all the internet speculation combined.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 05, 2018, 09:38:32 pm
Apparently the plane had airspeed indicator problems on its final FOUR flights! Surely enough opportunities for someone to check the pitot tubes and do some sort of investigation?  :-\

https://www.bbc.co.uk/news/world-asia-46094495 (https://www.bbc.co.uk/news/world-asia-46094495)

Not looking good for Lion Air, sadly it looks like the techs are going to take the fall even though you can bet it was management saying 'no delays, keep flying'. 

So. the two most likely causes appear to me to be either debris (insect etc) clogging the pitot tube or a leak (lose fittings) in the pitot-static system.  Of the two I suspect the later is more likely given the fact that the problem came and went on previous flights which I'd argue is less likely to happen with a clog than with a lose fitting.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 05, 2018, 09:42:30 pm
Aircraft manufacturers have probably figured pitot safety out better than random EE enthusiasts brainstorming here.
There's an airspeed alive callout and an 80-knot cross-check to catch gross pitot errors. It's extremely unlikely that this airplane took off with pitot covers installed (if that's the case, RFID tagged covers are a non-solution).

They have the FDR; they can hear roughly where the CVR is and are likely to recover it. That will tell a lot more than all the internet speculation combined.


I think pitot covers are completely ruled out as that would be glaringly obvious even if it was missed on the first flight with the problem -- how likely is it that they'd miss a pitot cover on four flights in a row?  It is possible a cover may have been on during the first flight and they chose to attempt to clean/repair the pitot tube rather than replace it.  Again, I think that's very unlikely. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on November 05, 2018, 09:56:36 pm
Not so easy. The manufacturer has to certify that this mechanism will not be a hazard, e.g. will never disable the aircraft during normal operation.
Lockout/tagout would make no functional change to the plane though, you just tie a key to the cap.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 05, 2018, 09:59:41 pm
Apparently the plane had airspeed indicator problems on its final FOUR flights! Surely enough opportunities for someone to check the pitot tubes and do some sort of investigation?  :-\

https://www.bbc.co.uk/news/world-asia-46094495 (https://www.bbc.co.uk/news/world-asia-46094495)

Not looking good for Lion Air, sadly it looks like the techs are going to take the fall even though you can bet it was management saying 'no delays, keep flying'.
I'm not trying to be flippant here, but the flight crew already took the fall and is likely to take the fall in the official findings as well.
This probably will not get an NTSB report due to where it happened (outside US and non-N carrier), but if it were an NTSB report, it would likely read:

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot's loss of airplane control due to spatial disorientation during the initial climb after takeoff in day visual meteorological conditions.
Contributing factors to the accident were confusing PFD displays due to unreliable airspeed measurements from the pitot-static systems, broken/layered clouds over water, providing a difficult horizon to use as an alternate visual reference for orientation. Additional factors in the accident were flat morning light conditions and inadequately addressed maintenance squawks on prior flights of the pitot-static system.

It's hard to say exactly what they're going to find, but the probable cause is almost certain to start with "The pilot's loss of control..."
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 05, 2018, 10:06:18 pm
Pitch + Power = Performance.
Any pilot can get rather close to a target airspeed with a known pitch+power (adjusted for altitude and temp).

I'm coming to this thread pretty late, but this is the whole ball of wax right here. I don't fly big iron, but the the laws of physics are the same for them as anybody else. The AF447 crew screwed up. If it was a pitot problem, this crew screwed up, too. The plane is flyable without IAS.

In fact, in the AF447 situation where all the plane's automatic systems punted, that was (and probably remains) a design defect IMO, because the computers hand the airplane back to the captain at the worse possible moment. A better approach would be for the computer itself to start flying the aircraft by attitude and notify the pilot accordingly.


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: glarsson on November 05, 2018, 10:38:51 pm
Aircraft manufacturers have probably figured pitot safety out better than random EE enthusiasts brainstorming here.
I'm not random.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: eugenenine on November 05, 2018, 10:47:48 pm
Not so easy. The manufacturer has to certify that this mechanism will not be a hazard, e.g. will never disable the aircraft during normal operation.
Lockout/tagout would make no functional change to the plane though, you just tie a key to the cap.

I was going to say the ignition key and then post the ignition key from Airplane II but I couldn't find a clip of it.

seems like they could just put a string on the tube cover and have a little suction cup on the other end that sticks to the front window of the airplane.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on November 05, 2018, 10:56:27 pm
So. the two most likely causes appear to me to be either debris (insect etc) clogging the pitot tube or a leak (lose fittings) in the pitot-static system.  Of the two I suspect the later is more likely given the fact that the problem came and went on previous flights which I'd argue is less likely to happen with a clog than with a lose fitting.
Brian
Yes, insects nesting in pitot tubes have caused crashes before and they cant bee seen by external visual check i heard.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: eugenenine on November 06, 2018, 02:13:36 am
sounds like they need a way to divert the jet engine thrust into the tube for a second to clear it.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 06, 2018, 02:31:16 am
sounds like they need a way to divert the jet engine thrust into the tube for a second to clear it.
The pitot tubes are generally up front by the nose on multi-engine aircraft. They need to be in undisturbed air to sense properly.

They're nowhere near the engines and a blast of jet engine thrust would only serve to destroy the tubing and sensors behind. (The system measures the stagnation pressure and relates that back to airspeed. That stagnation sensing loop is closed [or very nearly closed].)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: amyk on November 06, 2018, 03:21:39 am
https://patents.google.com/patent/US3380298

"Device for purging pitot tubes" patented 1968-04-30. Essentially a valve that can disconnect the sensors and then connect the pitot to a compressed air source to blow out any obstructions from behind. Do planes have something similar?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 06, 2018, 06:24:14 am
https://patents.google.com/patent/US3380298

"Device for purging pitot tubes" patented 1968-04-30. Essentially a valve that can disconnect the sensors and then connect the pitot to a compressed air source to blow out any obstructions from behind. Do planes have something similar?


I don't think any such devise has been employed outside of testing.  Here's the concern...  First, it may not work and second, if anything goes wrong you could destroy a lot of expensive avionics.  Also, such a devise would be limited to ground use and could never be trusted in-flight.  A competent service technician or team of such would know what to do to isolate the problem and fix it -- this happens ALL THE TIME!  I suspect the ground crew were told they have 30 minutes before the next flight and if it isn't fixed before then they'd fly just as they did the previous three flights with the problem.  A bit like NASA being pressured to launch the Challenger because they wanted there teacher in space.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: eugenenine on November 06, 2018, 12:26:57 pm
https://patents.google.com/patent/US3380298

"Device for purging pitot tubes" patented 1968-04-30. Essentially a valve that can disconnect the sensors and then connect the pitot to a compressed air source to blow out any obstructions from behind. Do planes have something similar?

someone should patent this for cleaning pilot tubes

(https://images.prod.meredith.com/product/3c5286530722e9bcc6c69ac524bbe39b/1524025801742/l/yoassi-16-long-bottle-brush-cleaner-tube-bottle-washing-brush-for-washing-baby-bottle-water-bottles-mugs-wine-stemware-narrow-neck-brewing-bottles)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Homer J Simpson on November 07, 2018, 10:36:06 am


Boeing and FAA to issue advice to airlines on 737 Max jets AoA sensor.


"potentially suspect flight-control software that can confuse pilots and lead to a steep descent of the affected aircraft model"



https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339 (https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on November 07, 2018, 12:16:56 pm
Boeing and FAA to issue advice to airlines on 737 Max jets AoA sensor.
"potentially suspect flight-control software that can confuse pilots and lead to a steep descent of the affected aircraft model"
https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339 (https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339)

That sounds like it's ultimately going to be pilot error.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: PA0PBZ on November 07, 2018, 02:06:53 pm
https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339 (https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339)

Paywall  :--
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BradC on November 07, 2018, 02:40:39 pm
https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339 (https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339)

Paywall  :--

Worked here.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: PA0PBZ on November 07, 2018, 02:57:18 pm
Worked here.

Strange...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Koen on November 07, 2018, 05:07:21 pm
Googling "Boeing Issues Safety Alert Following Lion Air Crash" did the trick for me.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: station240 on November 07, 2018, 06:32:39 pm
https://www.abc.net.au/news/2018-11-08/lion-air-flight-had-crucial-sensor-replaced-prior-to-fatal-crash/10475468 (https://www.abc.net.au/news/2018-11-08/lion-air-flight-had-crucial-sensor-replaced-prior-to-fatal-crash/10475468)
Quote
A crucial sensor that is the subject of a Boeing safety bulletin was replaced on a Lion Air jet the day before it plunged into the Java Sea and possibly worsened other problems with the plane, Indonesian investigators have revealed.

Indonesia's National Transportation Safety Committee (NTSC) said it had agreed with Boeing on procedures that the airplane manufacturer should distribute globally on how flight crews can deal with "angle of attack" sensor problems following the October 29 crash that killed all 189 people on board.

Experts say the angle of attack is a crucial parameter that helps the aircraft's computers understand whether its nose is too high relative to the current of air.

The sensor keeps track of the angle of the aircraft nose relative to oncoming air to prevent the plane from stalling and diving.

But a Boeing statement said a safety bulletin, sent to airlines this week, directs flight crews to existing guidelines on how they should respond to erroneous "angle of attack" data.

"The point is that after the AOA [sensor] is replaced the problem is not solved, but the problem might even increase. Is this fatal? NTSC wants to explore this," he said.

So in other words, simply replacing the sensor can not only not work, but can make the problem worse.
I assume as you then have an un-calibrated sensor.

Quote
Transport safety committee chairman Soerjanto Tjahjono said airspeed indicator malfunctions on the jet's last four flights, which were revealed by an analysis of the flight data recorder, were intertwined with the sensor issue.

So they have bad readings from both the Angle of Attack and Airspeed sensors, this sounds more like a wiring/electronics issue to me.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Homer J Simpson on November 07, 2018, 06:33:42 pm

Boeing jet crashed in Indonesia a day after key sensor replaced

"Lion Air's first two attempts to address the airspeed indicator problem didn't work and for the Boeing 737 MAX 8 plane's second to last flight on Oct. 28, the angle of attack sensors were replaced, Tjahjono said.

On that flight, from Bali to Jakarta, the pilot's and copilot's sensors disagreed. The 2-month-old plane went into a sudden dive minutes after takeoff, which the pilots were able to recover from. They decided to fly on to Jakarta at a lower than normal altitude."



https://komonews.com/news/nation-world/boeing-jet-crashed-in-indonesia-a-day-after-key-sensor-replaced


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: alsetalokin4017 on November 07, 2018, 07:42:18 pm
Boeing and FAA to issue advice to airlines on 737 Max jets AoA sensor.
"potentially suspect flight-control software that can confuse pilots and lead to a steep descent of the affected aircraft model"
https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339 (https://www.wsj.com/articles/boeing-faa-to-issue-safety-alerts-following-lion-air-crash-1541562339)

That sounds like it's ultimately going to be pilot error.

Well, sure, but it all depends on how far back you go to "ultimately". Myself, I'd say that the major pilot error was to accept the aircraft for flight in the first place, after maintenance on the sensor system. Let a test pilot crew test such critical systems without pax on board first!

But once off the ground, the situation is something like this: you are driving along, fat dumb and happy, at night on a smoothly paved road. Suddenly the pavement ends and you are bouncing along on ruts and potholes, and suddenly a thunderstorm starts dumping hail on you, and your windshield wipers short out, your headlights fail and your horn inexplicably starts blaring. Right at that moment a kangaroo leaps out onto what's left of the road, your brakes fail and you run into it, destroying your vehicle and killing all on board. Ultimately... it's driver error, for not avoiding the 'roo. Innit?

I am not disagreeing though. The pilots evidently did not perform the correct actions for dealing with unreliable air data, therefore "pilot error", but you really have to consider the environment and the demands of the task at hand. The "roo in the road" above doesn't even come close to the disorientation and distractions that must have been happening in that cockpit.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 07, 2018, 07:58:22 pm
That sounds like it's ultimately going to be pilot error.
Well, sure, but it all depends on how far back you go to "ultimately". Myself, I'd say that the major pilot error was to accept the aircraft for flight in the first place, after maintenance on the sensor system. Let a test pilot crew test such critical systems without pax on board first!
You seriously believe that airliners are commonly flown by test pilots without pax after maintenance items? No way that happens after minor maintenance. It gets a signoff from maintenance and the next flight has pax on board. Ultimately, it's the crew's discretion whether or not to take an aircraft, but not taking an aircraft because maintenance was just performed is a short road to unemployment at an air carrier.
But once off the ground, the situation is something like this: you are driving along, fat dumb and happy, at night on a smoothly paved road. Suddenly the pavement ends and you are bouncing along on ruts and potholes, and suddenly a thunderstorm starts dumping hail on you, and your windshield wipers short out, your headlights fail and your horn inexplicably starts blaring. Right at that moment a kangaroo leaps out onto what's left of the road, your brakes fail and you run into it, destroying your vehicle and killing all on board. Ultimately... it's driver error, for not avoiding the 'roo. Innit?

I am not disagreeing though. The pilots evidently did not perform the correct actions for dealing with unreliable air data, therefore "pilot error", but you really have to consider the environment and the demands of the task at hand. The "roo in the road" above doesn't even come close to the disorientation and distractions that must have been happening in that cockpit.
That is a pretty reasonable description of the hand that the Air France 447 crew was handed (and that they were unable to handle).

Lion Air was a daytime flight, with largely visual conditions prevailing. I'm going to fully withhold judgment until more information (including CVR transcripts) is available, but based on the information available, this seems a lot closer to "speedometer was covered up by a piece of paper fluttering around the cabin and operator couldn't keep the car between 40 and 80 mph without that reference" than the scenario you describe (which I'd argue was still salvageable by fully-qualified crew, on an average day, but not by that crew on that evening).
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 07, 2018, 09:56:24 pm
A new player in this crash is the AOA indicator, or more accurately, the AOA probe.  For some reason the AOA transmitter was replaced and I'm kind of wondering how this relates to the pitot/static system.  The AOA indicator should indicate the angle the aircraft is flying relative to the air they're flying in and if the new transmitter was not installed properly it could give an erroneous AOA indication.

Additionally, since they appear to have been flying with autopilot the flight control outputs would have been determined by the flight computer taking into account the data from the sensors.  It appears that there maybe an issue in the software as it relates to the AOA sensor data and on a previous flight the plane went into a dive that the pilots were able to recover from.  Ultimately, with as many issues as they had in the previous flights it is unacceptable that the plane remained in service until the problem was nailed down. 

So, the lawyers will have a field day with everyone to blame.  The pilots, the ground crew, the airline management, and Boeing.  I can well imagine a bunch of lawyers are at this very moment placing orders for new cars and a second home.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 07, 2018, 11:03:45 pm
AOA seems to be a second pressure port on the pitot probe. One for airspeed, another for critical (stall) angle.
There is a cal file specific to the aircraft. I'm not sure if it was a generic pitot part that was swapped out and cal file left alone or corrupted...

How was the autopilot working for the previous flights?
With a pitot discrepancy, Airbus goes to manual mode.
It seems odd previous flights had issues after takeoff and somehow did fine afterwards.

There are billions of dollars at stake here, I doubt the blame will be proper between parties.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on November 08, 2018, 01:44:47 am
Time for a AirFrance thread reminder, so whatever potentially disastrous during flight always:
1:Aviate , 2:Navigate , 3:Communicate. Also for pilots taking off is optional, landing is mandatory.
Just sayin!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on November 08, 2018, 02:00:04 am
Lion Air was a daytime flight, with largely visual conditions prevailing. I'm going to fully withhold judgment until more information (including CVR transcripts) is available, but based on the information available, this seems a lot closer to "speedometer was covered up by a piece of paper fluttering around the cabin and operator couldn't keep the car between 40 and 80 mph without that reference" than the scenario you describe (which I'd argue was still salvageable by fully-qualified crew, on an average day, but not by that crew on that evening).

At this stage that's my guess too (with my obvious in-depth knowledge of aviation with one flight and 3hrs flying time under my belt  ::) ).
No bad weather, daytime, maybe some clouds making horizon reference a bit tricky, but with no actual fault in the plane control systems, it should have been work-aroundable and completely flyable.
But of course one small thing can often send you down a path that doesn't end well.
They did report issues and were returning to the airport at the time of the incident, so should have been in super-alert troubleshooting mode fresh into the lfight, and not half way across the atlantic 8 hours in and tired and shit suddenly hits the fan.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 08, 2018, 05:43:16 am
Lion Air was a daytime flight, with largely visual conditions prevailing. I'm going to fully withhold judgment until more information (including CVR transcripts) is available, but based on the information available, this seems a lot closer to "speedometer was covered up by a piece of paper fluttering around the cabin and operator couldn't keep the car between 40 and 80 mph without that reference" than the scenario you describe (which I'd argue was still salvageable by fully-qualified crew, on an average day, but not by that crew on that evening).

At this stage that's my guess too (with my obvious in-depth knowledge of aviation with one flight and 3hrs flying time under my belt  ::) ).
No bad weather, daytime, maybe some clouds making horizon reference a bit tricky, but with no actual fault in the plane control systems, it should have been work-aroundable and completely flyable.
But of course one small thing can often send you down a path that doesn't end well.
They did report issues and were returning to the airport at the time of the incident, so should have been in super-alert troubleshooting mode fresh into the lfight, and not half way across the atlantic 8 hours in and tired and shit suddenly hits the fan.

Modern commercial fly by wire AC don't let the pilot have full control even when the autopilot is disengaged.  The AOA factor is critical and I expect Boeing will be releasing updated flight control software sometime in the not too distant future. 

In order for a pilot to override the control decisions of the computer the pilots must deactivate a number of systems and until they do this the computer is still in charge.

Beyond what I've already posted on this I think what Boeing did today was the first step in addressing an actual control problem that can occur when the right, or wrong, set of airspeed, altitude and AOA data is presented to the computer.  The fact that the previous flight had pretty similar problems, issued a Pan-Pan and asked to return, but then the problem went away and they decided to continue with the flight would not be permitted most places in the world but Lion Air appears to operate with the schedule being more important than safety.

There are many at fault here and the consequence is going to be expensive.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 08, 2018, 06:57:20 am
However, the Boeing 737 is NOT a fly-by-wire aircraft.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: IanMacdonald on November 08, 2018, 08:00:27 am
1:Aviate , 2:Navigate , 3:Communicate.

4: M....bate.

Though  if you are flying a Dalek mothership you may have more success with:
1:Aviate , 2:Navigate , 3:Exterminate 4: Communicate.
Than with 3 and 4 in conventional order. By which time The Doctor has gotten away.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 08, 2018, 08:02:30 am
The fact that the previous flight had pretty similar problems, issued a Pan-Pan and asked to return, but then the problem went away and they decided to continue with the flight would not be permitted most places in the world but Lion Air appears to operate with the schedule being more important than safety.
The captain/pilot-in-command has significant discretion as to the conduct of the flight. I can think of several valid reasons a flight may initially decide they need to return only to overcome the problem and elect to continue. A mis-programmed FMS/FD may very well give the crew reason for concern and then the crew may overcome that and safely continue the flight. Weather is another. An abnormal or emergency may crop up that is subsequently remedied by reference to the QRH/checklist procedures. Continuing may very well be the safest (or equally safe and more economical) choice.

BA268 is a classic example of that. They lost an engine (with external flames) 300 feet into the climb off LAX en route to Heathrow. ATC declared an emergency on their behalf (also permitted by their job orders (https://www.faa.gov/documentLibrary/media/Order/7110.65X_ATC_w_chg_1_and_chg_2.pdf) (section 10-1)). Crew shut the engine down, continued the climb, and did an assessment to continue the flight rather than dump fuel and return. Passing the east coast of the US, another assessment by them allowed them to continue for England. Ultimately, crew declared an emergency for fuel and landed in Manchester, short of Heathrow.

The first actual section of Federal law governing aviation in the US is 14 CFR 91.3 (https://www.law.cornell.edu/cfr/text/14/91.3), which reads:
Quote
§ 91.3 Responsibility and authority of the pilot in command.
(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.

(b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

(c) Each pilot in command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator.
Airline Ops are additionally governed by part 121, which includes 14 CFR 121.557 (https://www.law.cornell.edu/cfr/text/14/121.557), with substantially similar text. Of course there is pressure in the airline world to complete trips as planned. Because the pilots are generally the first ones to arrive at the scene of the crash, there's also a high degree of pressure to complete flights safely.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: IanMacdonald on November 08, 2018, 08:16:25 am
"Ultimately, crew declared an emergency for fuel and landed in Manchester, short of Heathrow."

Which underlines that in aviation, once you are in an unfamiliar situation you may encounter other unfamiliar situations. In this case an increased fuel burn. 
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: khs on November 08, 2018, 08:19:25 am
The AOS sensor sounds harmless.

But it is not.

As I've learned, the AOS sensor controls the trim system of the aircraft.

The trim system of the aircraft sounds harmless.

But it is not.

As I've learned (from the comments from avherald.com), trimming is not a little bit nose up or down.
In the worst case, trimming cannot be compensated by the pilot's input, because the range of the trim system is greater(!!) than the range of the stick.

If the AOS sensor is faulty, the STAB TRIM CUTOUT switches must be set to CUTOUT by the pilot.

I do not understand why Boeing does not turn off the trim system by software when the AOS sensor generates bad data.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 08, 2018, 08:32:18 am
IIRC, the issue was the flight crew's uncertainty that they could access all the fuel onboard during one-engine-INOP operations, not that they didn't have enough overall fuel onboard.
IOW, they were concerned about fuel starvation, not fuel exhaustion.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 08, 2018, 09:42:47 am
IIRC, the issue was the flight crew's uncertainty that they could access all the fuel onboard during one-engine-INOP operations, not that they didn't have enough overall fuel onboard.
IOW, they were concerned about fuel starvation, not fuel exhaustion.

Then the FAA tried to fine them for not being airworthy. A UK aircraft in international or UK airspace when the fuel emergency was called. The UK CAA (their equivalent of the FAA) disagreed and said the plane was certified airworthy with only 3 engines. I gather the FAA accepted that in the end.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 08, 2018, 02:02:05 pm
They did. The FAA concern was over the engine out in California, not the later emergency in Manchester. But the FAA backed down as the aircraft was certified to operate on 3. (Uncomplicated loss of engine in a 747 is an "abnormal" procedure, not an "emergency" procedure.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: IanMacdonald on November 08, 2018, 03:41:34 pm
Large airliners undergo substantial changes in elevator trim, particularly when landing flaps are deployed. It is often marginal as to whether the pilots could exert enough force on the controls to maintain attitude without the help of the trim tabs. Conversely if a trim tab goes to an extreme position and cannot be reset, this can be a mission critical situation.

Interestingly, in the event of elevator drive failure it is often possible for a skilled pilot to make a safe landing by flying the plane with the trim control.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 08, 2018, 11:23:32 pm
However, the Boeing 737 is NOT a fly-by-wire aircraft.


It's not a 100% fly by wire AC but it does have fly-by-wire control of spoilers.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 09, 2018, 12:22:55 am
However, the Boeing 737 is NOT a fly-by-wire aircraft.


It's not a 100% fly by wire AC but it does have fly-by-wire control of spoilers.


Brian

I learned something new. You're right, but ONLY for the ~200 737-MAX's that have been delivered. Most of the thousands of 737's out there are 0% fly-by-wire. So for the MAX, let's call it 5% to be generous? Spoiler use in normal flight is limited to descents and landings. Most of its advanced features have to be enabled by the pilots, and most features are locked out when the flaps are not extended, even if turned on.
http://www.b737.org.uk/max-spoilers.htm (http://www.b737.org.uk/max-spoilers.htm)

I'd be pretty surprised if the spoilers were a negative factor in this crash.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Bratster on November 09, 2018, 03:14:11 am
Quote
I have a Raspberry Pi + $12 USB Software Defined Radio in my garage
o you share? I use a proper Equipment for.

I wouldn't mind setting up a receiver, but i can't find a map of existing installations?

https://flightaware.com/adsb/coverage#feeder-sites

I just got the stuff to set up a receiver and came across this page that shows the existing feeder sites and coverage.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: alsetalokin4017 on November 09, 2018, 03:31:11 am
Lion Air was a daytime flight, with largely visual conditions prevailing. I'm going to fully withhold judgment until more information (including CVR transcripts) is available, but based on the information available, this seems a lot closer to "speedometer was covered up by a piece of paper fluttering around the cabin and operator couldn't keep the car between 40 and 80 mph without that reference" than the scenario you describe (which I'd argue was still salvageable by fully-qualified crew, on an average day, but not by that crew on that evening).

At this stage that's my guess too (with my obvious in-depth knowledge of aviation with one flight and 3hrs flying time under my belt  ::) ).
No bad weather, daytime, maybe some clouds making horizon reference a bit tricky, but with no actual fault in the plane control systems, it should have been work-aroundable and completely flyable.
But of course one small thing can often send you down a path that doesn't end well.
They did report issues and were returning to the airport at the time of the incident, so should have been in super-alert troubleshooting mode fresh into the lfight, and not half way across the atlantic 8 hours in and tired and shit suddenly hits the fan.

Actually the weather was very hazy so, over the water, the horizon would have been very indistinct and maybe even invisible. And the aircraft was undergoing radical pitch excursions resulting in wildly varying g-forces, and several different audible alarms were going off in the cockpit. Cabin crew, unsecured in seats, may have been injured or having to deal with passenger injuries due to the aircraft's attitude changes during the struggle to maintain control. This is why I described the "roo" situation as I did. In many ways this event was _worse_ than AF447, which was in a stable "mushing stall" all the way to the water and could have been flown out to normal flight had the pilots actually flown it out by simply lowering the nose and adding power. This aircraft was broken, and even if the pilots could have recovered it, it would still be broken and causing problems all the way until landed -- or crashed.

So yes -- pilot error, but in an environment where it was incredibly easy to make errors and be distracted, and at an altitude that did not allow time for evaluation -- or mistakes.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 09, 2018, 08:16:17 am
When the cabin crew is seated in their jumpseats, they are typically secured by shoulder straps. This plane was in trouble so soon after takeoff, I doubt the cabin crew was ever given clearance to move around, nor are they likely to do so on their own when things are clearly going wrong. Not that it mattered in the end, dead is dead.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 09, 2018, 11:02:39 pm
However, the Boeing 737 is NOT a fly-by-wire aircraft.


It's not a 100% fly by wire AC but it does have fly-by-wire control of spoilers.


Brian

I learned something new. You're right, but ONLY for the ~200 737-MAX's that have been delivered. Most of the thousands of 737's out there are 0% fly-by-wire. So for the MAX, let's call it 5% to be generous? Spoiler use in normal flight is limited to descents and landings. Most of its advanced features have to be enabled by the pilots, and most features are locked out when the flaps are not extended, even if turned on.
http://www.b737.org.uk/max-spoilers.htm (http://www.b737.org.uk/max-spoilers.htm)

I'd be pretty surprised if the spoilers were a negative factor in this crash.


All aircraft have autopilot and this is true for more than 50 years -- these system permit the computer to control the aircraft even in AC that are not fly-by-wire.  So, the fact remains that modern aircraft place a computer between the pilot and the control surfaces even when the plane is not fly-by-wire in the technical sense.  In operation the computer fly's the plane most of the time including climb-out and descent.  If the pilots are not well versed in the methods to arrest control from the computer they are in trouble -- and again, this also applies to non fly-by-wire AC though to a lessor extent. 

It will be interesting to find out which system, the pilots or the computer, were responsible for the dive that doomed them!


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 11, 2018, 05:35:01 pm
But of course one small thing can often send you down a path that doesn't end well.

Just a nit here, but few aviation accidents are caused by one thing going wrong. There is usually a rather long accident chain. In this case, we already know that there is a) potentially a design error b) definitely a flight manual documentation error (this is what the AD that Boeing put out modifies) c) a known sensor issue that was sent for repair d) a plane that was not test-flown after a sensor repair and then e,f,... whatever happened in the cockpit that we do not know about yet, but I'm willing to bet that more than one mistake was made.

I'm not an airline pilot, but I am an instrument-rated private pilot with about 500 hours and I'm also a voracious consumer of accident reports.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 11, 2018, 05:45:06 pm
Just for reference, this is the actual emergency Airworthiness Directive that Boeing has sent out:


https://c-3sux78kvnkay76x24znkgox78iax78x78ktzx2eius.g00.flyingmag.com/g00/3_c-3ccc.lreotmsgm.ius_/c-3SUXKVNKAY76x24nzzvyx3ax2fx2fznkgox78iax78x78ktz.iusx2fcv-iutzktzx2favrugjyx2f8674x2f77x2fH393-SGD-GJ-7763.vjl_$/$/$/$/$/$?i10c.ua=1&i10c.dv=14 (https://c-3sux78kvnkay76x24znkgox78iax78x78ktzx2eius.g00.flyingmag.com/g00/3_c-3ccc.lreotmsgm.ius_/c-3SUXKVNKAY76x24nzzvyx3ax2fx2fznkgox78iax78x78ktz.iusx2fcv-iutzktzx2favrugjyx2f8674x2f77x2fH393-SGD-GJ-7763.vjl_$/$/$/$/$/$?i10c.ua=1&i10c.dv=14)

It is, in its entirety, an update to the flight manual.

I see three basic elements to it:

 1. x, y, and z are signs of a AOA sensor failure, with certain confusing instrument indications, including a potentially erroneous and changing minimum speed bar on the ASI
 2. pilots should respond to such failures by disconnecting the auto stabilizer trim system
 3. pilots should expect to need to use extra control force to overcome the auto stab system until it has been disconnected

Based on this, it would seem that Boeing suspects that the airplane was flyable, but that the crew did not react as they should, perhaps due to poor training or lack of awareness of this particular failure mode. Of course, that's what Boeing would say. OTOH, crashes are really bad PR and they'd ground the planes if they suspected there was areal system problem.






Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 12, 2018, 05:20:56 pm
Just for reference, this is the actual emergency Airworthiness Directive that Boeing has sent out:


https://c-3sux78kvnkay76x24znkgox78iax78x78ktzx2eius.g00.flyingmag.com/g00/3_c-3ccc.lreotmsgm.ius_/c-3SUXKVNKAY76x24nzzvyx3ax2fx2fznkgox78iax78x78ktz.iusx2fcv-iutzktzx2favrugjyx2f8674x2f77x2fH393-SGD-GJ-7763.vjl_$/$/$/$/$/$?i10c.ua=1&i10c.dv=14 (https://c-3sux78kvnkay76x24znkgox78iax78x78ktzx2eius.g00.flyingmag.com/g00/3_c-3ccc.lreotmsgm.ius_/c-3SUXKVNKAY76x24nzzvyx3ax2fx2fznkgox78iax78x78ktz.iusx2fcv-iutzktzx2favrugjyx2f8674x2f77x2fH393-SGD-GJ-7763.vjl_$/$/$/$/$/$?i10c.ua=1&i10c.dv=14)

It is, in its entirety, an update to the flight manual.

I see three basic elements to it:

 1. x, y, and z are signs of a AOA sensor failure, with certain confusing instrument indications, including a potentially erroneous and changing minimum speed bar on the ASI
 2. pilots should respond to such failures by disconnecting the auto stabilizer trim system
 3. pilots should expect to need to use extra control force to overcome the auto stab system until it has been disconnected

Based on this, it would seem that Boeing suspects that the airplane was flyable, but that the crew did not react as they should, perhaps due to poor training or lack of awareness of this particular failure mode. Of course, that's what Boeing would say. OTOH, crashes are really bad PR and they'd ground the planes if they suspected there was areal system problem.

Boeing seems to have acted quickly and responsibly here though time will tell.  And, as I pointed out before and in spite of the fact that this plane is not technically fly-by-wire, the computer interposes itself between the pilot and control surfaces in a myriad of ways so taking 100% manual control is rather more complicated than pressing a single button. 

Best guess is that the pilots were too 'heads down' trying to make sense of things and didn't notice the plane was in descent until it was too late.  Again, there is going to be blame enough for everyone and the lawyers will profit...


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 12, 2018, 07:58:17 pm
And, as I pointed out before and in spite of the fact that this plane is not technically fly-by-wire, the computer interposes itself between the pilot and control surfaces in a myriad of ways so taking 100% manual control is rather more complicated than pressing a single button. 

You have said this, and I'm pretty sure it's not correct in any operational sense in any Boeing airliner. Disconnecting the AP is indeed a single button push -- and that button is on the yoke, too, right where it can be pressed in an instant. The plane can also adjust the trim automatically, and as the AD makes clear, that can also be turned off. But even if not turned off, it can be overridden by the pilot's controls without any special action other than pushing or pulling harder than usual. Similarly, there's an  trim and automatic yaw damper on the rudder which the pilot can disengage, but he can also kick the rudder however he wants and the machine will obey.

Boeing has aircraft such as the 777 that have FBW, but their philosophy is quite a bit different than Airbus's. The machine will essentially inform the pilot that he is about to exceed the aircraft's envelope by making it increasingly difficult for him to assert his control input (by pushing back against his inputs), but it will not override him. Check out section 11.3 of this document: http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_11.pdf (http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_11.pdf)

So, though there are systems (electric, hydraulic) between the pilot an the control surfaces, the pilots commands ARE obeyed unless something has actually broken.

This is totally different from an Airbus aircraft, where the computer under "normal law" enforces the flight envelope no matter the control inputs. There are several other modes the aircraft can be in, such as "alternate law 1" where the plane continues to enforce most of the envelope except AOA and overspeed, and "alternate law 2" where only load factor is enforced, and of course "direct law" which is basically "you're on your own kid."



In this case, it looks like the computer might have pushed the nose down, but the pilot could have counterracted that with the normal controls, albeit, with extra force.


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 12, 2018, 08:40:24 pm
And, as I pointed out before and in spite of the fact that this plane is not technically fly-by-wire, the computer interposes itself between the pilot and control surfaces in a myriad of ways so taking 100% manual control is rather more complicated than pressing a single button. 
You have said this, and I'm pretty sure it's not correct in any operational sense in any Boeing airliner. Disconnecting the AP is indeed a single button push -- and that button is on the yolk, too, right where it can be pressed in an instant. The plane can also adjust the trim automatically, and as the AD makes clear, that can also be turned off. But even if not turned off, it can be overridden by the pilots controls without any special action other than pushing or pulling harder than usual.
The problem with applying continued force to overcome the airplane's trim is that the auto-trim will continue to trim against you (essentially by design). Airplane is on autopilot and trying to fly a course consistently lower than the aircraft is heading? The airplane will add nose-down trim. If the pilot continues to pull against that, they can, but the airplane will sense that the autopilot is not following the programmed pitch and will continue to trim nose down. On every aircraft I've flown, which is mostly piston singles and twins, but includes a few jets, pressing and holding the AP Disconnect switch will kill power to the auto-trim system and pitch trim motors.

Minor nit: it's "yoke" not "yolk"
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 12, 2018, 11:18:46 pm
Minor nit: it's "yoke" not "yolk"

Hah, I promised myself I would never do that again. Oh well.

I think we're in agreement. Yes, the AP/trim will work against you more and more but at the same time, that feeling of working against trim is going to be very familiar to any pilot who has ever flown with an AP. Particularly when you're having a "what is Otto doing now" moment, I can't think of anything more natural than disconnecting the AP and putting the plane into the state I want, while I figure out why the AP has different plans.

Admittedly, this is coming from someone whose time is mostly in older light singles with reliably unreliable autopilots.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 13, 2018, 02:54:18 pm
I suspect we agree on almost everything about this crash, at least based on what is known now.

One difference in larger aircraft than in the light singles that you have experience in is that many larger aircraft trim systems work by changing the angle of incidence of the horizontal stabilizer with respect to the fuselage. (It literally cranks the tail "nose up" or "nose down" usually with a jackscrew.) Systems like this have the capability to overpower the pilot's inputs to a much greater extent than the "flying trim tabs" on most light singles. (Among light singles, as far as I know the only common types to use this system are most Mooneys, Piper's TriPacer, and the Cessna 185.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 13, 2018, 07:17:50 pm
I don't know how long it will take for the formal report but I would expect an overview of the FDR and CVR within 4-6 weeks.  It may not answer all questions, but it should provide more details on the technical problems and, hopefully, address the factual situation with respect to which system, pilots or computer, produced the nose down attitude that resulted in the crash.  We can quibble over just how much automation this AC had but the fact remains this wasn't a purely manual AC and the pilots would need to do certain things to take the computer out of the loop. 

The facts about that particular truth should be clear as day in the FDR and the CDR should help elucidate the pilots actions during the 13 minutes of the flight. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 13, 2018, 07:39:27 pm
Boeing screwed up putting an extra (undocumented) "Maneuvering Characteristics Augmentation System" to compensate for "some unique aircraft handling characteristics."

It relies on the AOA sensor and automatically lowers the plane's nose into a dive if it figures a stall condition exists.

No way for pilots to know about it- Boeing has nothing mentioned in training, difference, manuals etc.
APA to American's pilots "This is the first description you, as 737 pilots, have seen"  :palm:

https://www.chicagotribune.com/business/ct-biz-boeing-indonesia-737-crash-20181113-story,amp.html (https://www.chicagotribune.com/business/ct-biz-boeing-indonesia-737-crash-20181113-story,amp.html)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on November 13, 2018, 08:19:12 pm
Boeing screwed up putting an extra (undocumented) "Maneuvering Characteristics Augmentation System" to compensate for "some unique aircraft handling characteristics."

It relies on the AOA sensor and automatically lowers the plane's nose into a dive if it figures a stall condition exists.

No way for pilots to know about it- Boeing has nothing mentioned in training, difference, manuals etc.
APA to American's pilots "This is the first description you, as 737 pilots, have seen"  :palm:

https://www.chicagotribune.com/business/ct-biz-boeing-indonesia-737-crash-20181113-story,amp.html (https://www.chicagotribune.com/business/ct-biz-boeing-indonesia-737-crash-20181113-story,amp.html)
How can it determine that ?

Airspeed ?
Are we back to suspecting blocked pitot tubes for this to happen ?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 13, 2018, 10:29:24 pm
I'm not sure who makes the 737 max sensor pitot or AOA sensor, it's kind of hush. Thales or UTC etc.

My understanding is the AOA sensor measures pressure at the wing leading edge and together with the pitot you get differential (wing) pressure indicating lift. Some sensors combine both (mechanically) with a second pressure port in the pitot sensor. AOA is not an absolute angle sensor.

If either pressure sensor is malfunctioning, software may act thinking there is a stall condition, there is no lift.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on November 13, 2018, 10:42:38 pm
Yes thanks, some further understanding here:
http://www.dynonavionics.com/aoa-pitot-probes.php (http://www.dynonavionics.com/aoa-pitot-probes.php)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 13, 2018, 11:11:07 pm
Well, we'll all guessing here, but I still would be very surprised if pilots were not mentally equipped for a "runaway" trim problem where the trim/AP does something unexpected. Even if the cause of this runaway is novel, the idea that it can happen, and what you would do in that case would hardly be.

Yes, I'm pulling this from my rear, but at the same time, it's such a basic airmanship thing: you are flying an airplane that has (not so) little motors that can adjust control surface trims and those motors are connected to a sophisticated box that, though pretty great, is fallible. You need to be ready to disconnect those motors in a hurry, and the "why is the control system doing this" question can be handled later.

Which is not to say that there isn't be a problem with the aircraft design -- it sounds like there very well may be. I just think that some of the fault is going to remain on the pilots.

Accidents can have more than one contributing cause.

by the way, here's a relevant page from a 737 QRH (not a -MAX, I'm sure) (http://jira.icesoft.org/secure/attachment/21680/qrh%20rev36%20-800%2027k.pdf (http://jira.icesoft.org/secure/attachment/21680/qrh%20rev36%20-800%2027k.pdf)) for runaway stab trim
(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=571235)

It does not get more straightforward than that.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 12:12:37 am
Yes, I'm pulling this from my rear, but at the same time, it's such a basic airmanship thing: you are flying an airplane that has (not so) little motors that can adjust control surface trims and those motors are connected to a sophisticated box that, though pretty great, is fallible. You need to be ready to disconnect those motors in a hurry, and the "why is the control system doing this" question can be handled later.

Which is not to say that there isn't be a problem with the aircraft design -- it sounds like there very well may be. I just think that some of the fault is going to remain on the pilots.

Accidents can have more than one contributing cause.
Given that the emergency AD is a slightly wordier version of "in case of runaway trim, follow the existing runaway trim procedure", it's a pretty safe bet that a lot of the blame is going to land on the dead guys up front.

No specific differences training, blah, blah, blah, don't care. You're right; it is a basic airmanship thing and there are several ways to kill the trim, 3 of which I believe are memory items.

The trim wheels are also not small (intentionally so) and make a clicking racket when in motion (also intentional):
https://www.youtube.com/watch?v=cQirIH_DuAs (https://www.youtube.com/watch?v=cQirIH_DuAs)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Homer J Simpson on November 14, 2018, 01:30:21 am


Pilots says Boeing didn't disclose 737's new control feature

https://komonews.com/news/nation-world/were-p-sed-pilots-says-boeing-didnt-disclose-737s-new-control-feature
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SiliconWizard on November 14, 2018, 01:43:30 am
Pilots says Boeing didn't disclose 737's new control feature
https://komonews.com/news/nation-world/were-p-sed-pilots-says-boeing-didnt-disclose-737s-new-control-feature

Hmm, now that's interesting.

"But if that nose-down command is triggered by faulty sensor readings — as suspected in the Lion Air crash — pilots can struggle to control the plane, which can go into a dive and perhaps crash, according to a Boeing safety bulletin and safety regulators."

This sounds fishy. Faulty sensor readings, as those sensors are redundant, should be caught (if they aren't caught, then it's a very serious design problem).

Any decent flight helper such as this anti-stall mechanism SHOULD be automatically disconnected (of course with a clear warning) in case of faulty sensor readings. This would be way too dangerous otherwise. Interested in knowing more about all this...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on November 14, 2018, 02:05:10 am
So how fast can that trim throw the plane into a completely vertical dive?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 02:19:54 am
"But if that nose-down command is triggered by faulty sensor readings — as suspected in the Lion Air crash — pilots can struggle to control the plane, which can go into a dive and perhaps crash, according to a Boeing safety bulletin and safety regulators."

This sounds fishy. Faulty sensor readings, as those sensors are redundant, should be caught (if they aren't caught, then it's a very serious design problem).
Suppose you have two independent pitot systems and they don't agree; which one is faulty? Suppose you have N independent pitot systems and they all agree but are all wrong (because of a common-mode maintenance failure, most likely); how do you automatically catch the fault?

Any decent flight helper such as this anti-stall mechanism SHOULD be automatically disconnected (of course with a clear warning) in case of faulty sensor readings. This would be way too dangerous otherwise. Interested in knowing more about all this...
IMO, we haven't established that the airplane can automatically "know" that a sensor reading is faulty. That's part (to a lot) of what the crew is there for. Unfortunately for this flight, that crew doesn't seem to have been up to the challenge of the hand they were dealt on that day.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 14, 2018, 02:43:59 am
Suppose you have two independent pitot systems and they don't agree; which one is faulty? Suppose you have N independent pitot systems and they all agree but are all wrong (because of a common-mode maintenance failure, most likely); how do you automatically catch the fault?

This. Furthermore, strange or divergent readings do not necessarily mean that any sensor is malfunctioning. You can have sensors on each wing and one wing might be stalled while the other is still flying. You can fly through a wind shear event that only effects one side of the airplane, or through another aircraft's wake turbulence, or get too slow while turning, or a combination of those factors -- all of which are the kinds of scenarios that have led to accidents and that one would imagine such a system is designed to detect.

It's a tricky business.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SiliconWizard on November 14, 2018, 03:57:25 am
"But if that nose-down command is triggered by faulty sensor readings — as suspected in the Lion Air crash — pilots can struggle to control the plane, which can go into a dive and perhaps crash, according to a Boeing safety bulletin and safety regulators."

This sounds fishy. Faulty sensor readings, as those sensors are redundant, should be caught (if they aren't caught, then it's a very serious design problem).
Suppose you have two independent pitot systems and they don't agree; which one is faulty? Suppose you have N independent pitot systems and they all agree but are all wrong (because of a common-mode maintenance failure, most likely); how do you automatically catch the fault?

If there is disagreement, it obviously doesn't matter which one is wrong to detect there is a malfunction. This case would warrant the disconnection of any automatic system that could rely on or even be influenced by those sensors, and issue a warning. First thing that happens is usually the disconnection of the autopilot, and I'm pretty sure that happens when there is a faulty pitot, at least on Airbus planes. This is the first thing that happened on the AF447 for instance, AFAIK. Of course, this could be different in this case. Maybe.

Any redundant sensor system that would give the same figures but all wrong, and that those wrong figures could still pass as valid would be severely badly designed IMO, or this would be a case of extreme bad luck. Usually the different sensors should be located at different spots, ideally from different vendors, etc, so this should be rather unlikely. If it still happened, it can usually be figured out by the calculators since they would likely give figures that make no sense physically. The case were the measurements would all still seem valid to the calculators is not impossible but not very likely.
This is the whole point of redundant systems.

Any decent flight helper such as this anti-stall mechanism SHOULD be automatically disconnected (of course with a clear warning) in case of faulty sensor readings. This would be way too dangerous otherwise. Interested in knowing more about all this...
IMO, we haven't established that the airplane can automatically "know" that a sensor reading is faulty.

See above. If it can't, then there's a serious design flaw, or extreme bad luck IMO. When it comes to faulty sensors, the most common case is the crew either not able to fly the plane without the corresponding readings, or normally able but troubled under high stress and starting to not trust ANY of the plane readings and warnings, leading to sometimes deadly maneuvers.

We'll see.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 14, 2018, 04:36:43 am
If there is disagreement, it obviously doesn't matter which one is wrong to detect there is a malfunction. This case would warrant the disconnection of any automatic system that could rely on or even be influenced by those sensors, and issue a warning. First thing that happens is usually the disconnection of the autopilot, and I'm pretty sure that happens when there is a faulty pitot, at least on Airbus planes. This is the first thing that happened on the AF447 for instance, AFAIK. Of course, this could be different in this case. Maybe.

In the AF447 scenario, the computer decided it did not have reliable air data, so it not only disconnected the autopilot, it dropped into alternate law. Basically, the computer just punted and said "your airplane!" This might seem like reasonable behavior, but one might imagine that handing a degraded airplane to a pilot at the very worst moment is not a satisfactory failure mode, and in the AF447 scenario the outcome was obviously bad.

What else could the computer have been programmed to do? It could have perhaps dropped into an attitude-based straight-and-level flight mode, and made an annunciation inviting the pilots to take over, but not insisting that they do so that very instant.

But it's easy to second-guess these sorts of systems. It's not nearly as easy to design them so that they always do the thing that seems smartest in retrospect.

Any redundant sensor system that would give the same figures but all wrong, and that those wrong figures could still pass as valid would be severely badly designed IMO, or this would be a case of extreme bad luck.

I think you are underestimating the difficulty of this problem, because unusual attitudes and airspeeds are going to generate odd readings, and these are the exact situations -- not totally predictable -- where an AOA system is interesting.

Yes, one solution would be to have an array of AOA sensors from different vendors using different technologies, but you have to draw the line somewhere and you still need to integrate the data, and you still have to deal with the possibility that sensor #n, giving a strange reading is giving a correct strange reading. Maybe one sensor is at the wing root and another is at the tip, and the root is stalled and the tip is not. Or one wing is stalled and the other is not. Or both roots and one tip, but not the other, etc. Maybe the wing is physically damaged in some way that affects airflow and the sensor is correctly reporting that. All of those are aerodynamic situations that can happen.

Usually the different sensors should be located at different spots, ideally from different vendors, etc, so this should be rather unlikely.

But if they are in different spots, they're measuring different things. And "unlikely" is the exact problem. These aircraft are going to be flown 10's of thousands of hours and most of them are never going to ever get near a stall condition in their entire operational lives. Everything interesting an AOA system does is in well into the regime of "unlikely."



Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 11:22:22 am
"But if that nose-down command is triggered by faulty sensor readings — as suspected in the Lion Air crash — pilots can struggle to control the plane, which can go into a dive and perhaps crash, according to a Boeing safety bulletin and safety regulators."

This sounds fishy. Faulty sensor readings, as those sensors are redundant, should be caught (if they aren't caught, then it's a very serious design problem).
Suppose you have two independent pitot systems and they don't agree; which one is faulty? Suppose you have N independent pitot systems and they all agree but are all wrong (because of a common-mode maintenance failure, most likely); how do you automatically catch the fault?
If there is disagreement, it obviously doesn't matter which one is wrong to detect there is a malfunction. This case would warrant the disconnection of any automatic system that could rely on or even be influenced by those sensors, and issue a warning. First thing that happens is usually the disconnection of the autopilot, and I'm pretty sure that happens when there is a faulty pitot, at least on Airbus planes. This is the first thing that happened on the AF447 for instance, AFAIK. Of course, this could be different in this case. Maybe.

Any redundant sensor system that would give the same figures but all wrong, and that those wrong figures could still pass as valid would be severely badly designed IMO, or this would be a case of extreme bad luck. Usually the different sensors should be located at different spots, ideally from different vendors, etc, so this should be rather unlikely. If it still happened, it can usually be figured out by the calculators since they would likely give figures that make no sense physically. The case were the measurements would all still seem valid to the calculators is not impossible but not very likely.
This is the whole point of redundant systems.
It turns out the airplane has to house and lift all these redundant systems into the air and carry them around the world. There's a real cost (in $$ and in safety) to excess weight in an airplane and a genuine engineering challenge to make the planes as safe as feasible, but when you add weight to an airplane, all else being equal, almost nothing good happens to safety. Runway performance is degraded, climb performance is degraded, range/fuel efficiency is degraded, stress on the tires and brakes is increased (longer, heavier, faster takeoff roll, more energy to dissipate in an RTO, etc), all of which have negative safety implications. (About the only thing that gets better is one specific input into the calculation of turbulent air penetration speed.)

When you start taking multiple different sensors of different types or from different vendors, now you have more complexity overall and wider tolerances to determine whether these two sensors agree or not. If you start adding a third or more to help break the tie, you have even more. At some point, you paid more in reduced safety than the safety you bought with the more redundant design. (Very quickly you paid more in $$, of course.)

I suspect that you're quite good in whatever your specific field is. I also suspect that there's something counterintuitive about your field where something is done a certain way, for good reason, but that reason isn't obvious to an outsider. When that situation has a light shone on it, outsiders might assume that they know more and that the practitioners in the field are obviously wrong, or they can wonder why something is done that way and start from an assumption that the skilled practitioners have a reason for it.

cf. Chesterton's Fence (https://www.chesterton.org/taking-a-fence-down/)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on November 14, 2018, 01:03:08 pm
I don't know how long it will take for the formal report but I would expect an overview of the FDR and CVR within 4-6 weeks.

Did they find the CVR? I haven't been keeping up to date.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 01:07:45 pm
Not yet. (and the batteries on the locator beacon have now run out)

They found the AF447 black boxes though, long after they stopped pinging, so I'd expect there's a better than even chance that Lion Air's will be recovered eventually. It's mostly a question of how much money they are able to spend looking. I suspect it's properly "a lot".
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 14, 2018, 01:44:42 pm
The black box batteries are designed to operate the pinger for 30 days, and the crash was only 16 days ago. While it's correct to say we aren't hearing pings anymore, assuming the battery is the root cause of that is probably not correct.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 03:37:13 pm
Fair point taken.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 14, 2018, 06:54:20 pm
I'm not sure who makes the 737 max sensor pitot or AOA sensor, it's kind of hush. Thales or UTC etc.

My understanding is the AOA sensor measures pressure at the wing leading edge and together with the pitot you get differential (wing) pressure indicating lift. Some sensors combine both (mechanically) with a second pressure port in the pitot sensor. AOA is not an absolute angle sensor.

If either pressure sensor is malfunctioning, software may act thinking there is a stall condition, there is no lift.


AOA sensors typically have a vane that turns as the relative wind angle changes.  The vane will tend to rotate to the trailing edge of the wind-stream and as it does it reports that angle.  Think of it as kind of like a small windmill that has a vane to keep the prop pointed into the wind.

As I mentioned before even AC that are not full on fly-by-wire AC have systems controlled by the computer that interpose themselves between the flight control surfaces and the pilot and if the story now being painted about an automated system installed by Boeing is correct then it makes it out to be perhaps more of a concern than a full fly-by-wire AC as the pilots may not be fully aware of the computer being in control.

Not looking good for Boeing if true...


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on November 14, 2018, 06:58:17 pm
I don't know anything about plane nor piloting one, its just watching this commentary from a former Inspector General US Dept of Transportation makes me worry me as an avg Joe.

-> https://edition.cnn.com/videos/tv/2018/11/14/ns-nov-14-intvw-boeing-witholds-info-mary-schiavo.cnn
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 14, 2018, 07:07:42 pm
I don't know how long it will take for the formal report but I would expect an overview of the FDR and CVR within 4-6 weeks.

Did they find the CVR? I haven't been keeping up to date.


I haven't heard, but given the relatively shallow water and proximity near shore it is just a matter of time before they do find it.  I think the CVR may wind up being just as important as the FDR given the fact that the pilots have to do certain things to arrest control and at relatively low altitude if the computer commands a fairly steep dive they may only have a few seconds before its too late.

Hard to believe that 4.5 years later and we still haven't found MH370 -- if the Lion Air crash is something of a mystery the loss of MH370 is the mystery of the century.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 07:28:27 pm
I don't know anything about plane nor piloting one, its just watching this commentary from a former Inspector General US Dept of Transportation makes me worry me as an avg Joe.

-> https://edition.cnn.com/videos/tv/2018/11/14/ns-nov-14-intvw-boeing-witholds-info-mary-schiavo.cnn
IMO, as a pilot (albeit one with under 20 hours of jet time, though around 1500 hours in high performance singles and twins, and having attended type and recurrent trainings in simulators a handful of times), this is being overblown by the breathless media anxious for a story.

Yes, it seems like Boeing downplayed the differences in this airplane vs others on the same type certificate. Do I think that it rises to level of "not looking good for Boeing"? Sure. Do I think it rises to the level of "not being good for Boeing"? No, at least not yet. There's a lot of pressure to keep new airplanes on the same TC as existing designs. It seems very much expected that Boeing would pursue that course of action, including making design decisions with the constraint of "let's keep this airplane an A16WE".

From what I've read and viewed, I don't think that Boeing "withheld information" so much as "didn't highlight this particular system" and the same checklists and emergency procedures still applied as were applicable to the prior jets.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 14, 2018, 07:46:52 pm
Making the new airplane fuel efficient at the expense of handling, then quietly adding an undocumented MCAS system to make up for it to supposedly keep the plane backwards-compatible with previous generations of 737's... Right now, Boeing's mistake is rightly causing a shitstorm.
https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610 (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610)

But the root cause of the airspeed or AOA malfunction is still unknown. Even after Lion Air maintenance worked three times to fix the problem.

The plane's previous pilot encountered the same unintentional dive and then switched off the trim system, even though "it's not in the manual".
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 08:07:32 pm
Making the new airplane fuel efficient at the expense of handling, then quietly adding an undocumented MCAS system to make up for it to supposedly keep the plane backwards-compatible with previous generations of 737's... Right now, Boeing's mistake is rightly causing a shitstorm.
https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610 (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610)

But the root cause of the airspeed or AOA malfunction is still unknown. Even after Lion Air maintenance worked three times to fix the problem.

The plane's previous pilot encountered the same unintentional dive and then switched off the trim system, even though "it's not in the manual".
It is in the manual.

Previously posted by djacobow in this post:
https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1963691/#msg1963691 (https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1963691/#msg1963691)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 14, 2018, 10:25:09 pm
Making the new airplane fuel efficient at the expense of handling, then quietly adding an undocumented MCAS system to make up for it to supposedly keep the plane backwards-compatible with previous generations of 737's... Right now, Boeing's mistake is rightly causing a shitstorm.
https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610 (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610)

But the root cause of the airspeed or AOA malfunction is still unknown. Even after Lion Air maintenance worked three times to fix the problem.

The plane's previous pilot encountered the same unintentional dive and then switched off the trim system, even though "it's not in the manual".
It is in the manual.

Previously posted by djacobow in this post:
https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1963691/#msg1963691 (https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1963691/#msg1963691)

They omitted the total nightmare portion:

"The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released.
Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC."

The bulletin was just issued by Boeing Nov. 6
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 14, 2018, 10:35:20 pm
Making the new airplane fuel efficient at the expense of handling, then quietly adding an undocumented MCAS system to make up for it to supposedly keep the plane backwards-compatible with previous generations of 737's... Right now, Boeing's mistake is rightly causing a shitstorm.
https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610 (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610)

But the root cause of the airspeed or AOA malfunction is still unknown. Even after Lion Air maintenance worked three times to fix the problem.

The plane's previous pilot encountered the same unintentional dive and then switched off the trim system, even though "it's not in the manual".
It is in the manual.

Previously posted by djacobow in this post:
https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1963691/#msg1963691 (https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1963691/#msg1963691)

They omitted the total nightmare portion:

"The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released.
Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC."

The bulletin was just issued by Boeing Nov. 6

Yes, that's what can happen if you don't put the trim in cutout. If you follow the QRH and don't re-engage the trim, you're fine.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 11:06:22 pm
The bulletin was just issued by Boeing Nov. 6
That bulletin contains the following quote: (emphasis Boeing's)
Quote
Subject: Uncommanded Nose Down Stabilizer Trim Due to Erroneous Angle of Attack (AOA) During Manual Flight Only
Reason: To Emphasize the Procedures Provided in the Runaway Stabilizer Non Normal Checklist (NNC).

In other words, "follow the existing procedures as previously published".
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 14, 2018, 11:19:37 pm
... systems controlled by the computer that interpose themselves between the flight control surfaces and the pilot ...
You keep saying BETWEEN, trying to impose the definition of fly-by-wire on systems that aren't. The reality is ALONGSIDE; manual controls still work, and in most cases can overpower the automatics even if they are not switched off. The pilots are NOT disconnected from the control surfaces. Even with all the updates over decades, the 737 remains a very successful 1960's era design at the core.

The data recorder is going to have all we need to know about automatic vs manual inputs to the system, as well as what the instruments were saying at the time. It should also shoot down 95% of the speculation in this thread, once a decent analysis is released. But we really need that cockpit recorder to know what was going on in the heads of the pilots for those last 10 minutes.

However they got there, I'm guessing they ended up in an actual aerodynamic stall. Which, even when in full control, is likely not recoverable in the <5000 feet they had available. It fits the information we have so far. (For the benefit of the non-pilots, the way to regain control from a full stall is to enter a dive to regain airspeed, and then you have to recover from the dive. You lose a LOT of altitude in the process, very quickly.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 14, 2018, 11:33:20 pm
It's too easy to blame the pilots for "not flipping the off switch" in the stabilizer trim circus. Assuming that is the fatal error here.

The finest engineering and latest technology, and the system to prevent pilot error (stall) malfunctions with bad sensor data and ends up causing pilot error. An automatic control system fighting the pilot to his death.

Cryptic annunciators from the 1960's are still in the cockpit and yet the LCD displays are just mimicking old analog gauges and cannot offer any assistance to help a panicked crew. A lot of people have died due to these aircraft sensor malfunctions causing control system and pilot errors. I would come up with something to stop this shit instead of attributing it to human error and repeating the tragedies.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 11:35:23 pm
However they got there, I'm guessing they ended up in an actual aerodynamic stall. Which, even when in full control, is likely not recoverable in the <5000 feet they had available. It fits the information we have so far. (For the benefit of the non-pilots, the way to regain control from a full stall is to enter a dive to regain airspeed, and then you have to recover from the dive. You lose a LOT of altitude in the process, very quickly.)
I don't think that theory fits the flightradar24 data (https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/), nor does it fit the data of Boeing/FAA releasing an emergency AD about preventing stab trim runaway in the face of the stability augmentation system malfunction due to possibly erroneous AoA inputs. Neither of those is ironclad of course, but the high sink rate began to develop at a ground speed well in excess of the typical unaccelerated stall speed even fully clean.

It looks like the sink rate begins to develop with the ground speed in excess of 310 knots and the ground speed increases as the sink rate increases. That seems more consistent with a[n aerodynamically] controlled flight scenario rather than a departure [from controlled flight].
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 14, 2018, 11:36:20 pm
It's too easy to blame the pilots for "not flipping the off switch" in the stabilizer trim circus. Assuming that is the fatal error here.
Is it too much to ask a trained flight crew to follow checklists? IMO, it's not.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 15, 2018, 12:14:37 am
It's too easy to blame the pilots for "not flipping the off switch" in the stabilizer trim circus. Assuming that is the fatal error here.
Is it too much to ask a trained flight crew to follow checklists? IMO, it's not.
3 out of 4 flight crews seemed to handle this airplane's issues. Human error is well known to exist. Especially with a mystery control system that we also assume is flawless, containing no software errors from its human software engineers.

We don't know what happened in the cockpit that prevented the flight crew to follow a checklist. The alarms, stick shaking and sharp dive causing near zero G, wonky airspeed may have been part of it.

At some point it's like engineering has given up on humans, their reliability is poor and they are error-prone, so embedded systems are trying to take over.

Cars are heading full force towards self driving. I have already seen "driver assist" technology with automobiles malfunction.
The radar malfunctions in rain/snow and thinks you are going to hit an obstacle on a good puddle splash. Next gen is full brakes/steering/accelerator capability  :o
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 15, 2018, 12:40:13 am
... systems controlled by the computer that interpose themselves between the flight control surfaces and the pilot ...
You keep saying BETWEEN, trying to impose the definition of fly-by-wire on systems that aren't. The reality is ALONGSIDE; manual controls still work, and in most cases can overpower the automatics even if they are not switched off. The pilots are NOT disconnected from the control surfaces. Even with all the updates over decades, the 737 remains a very successful 1960's era design at the core.

The data recorder is going to have all we need to know about automatic vs manual inputs to the system, as well as what the instruments were saying at the time. It should also shoot down 95% of the speculation in this thread, once a decent analysis is released. But we really need that cockpit recorder to know what was going on in the heads of the pilots for those last 10 minutes.

However they got there, I'm guessing they ended up in an actual aerodynamic stall. Which, even when in full control, is likely not recoverable in the <5000 feet they had available. It fits the information we have so far. (For the benefit of the non-pilots, the way to regain control from a full stall is to enter a dive to regain airspeed, and then you have to recover from the dive. You lose a LOT of altitude in the process, very quickly.)


The pilot in a non-fly-by-wire AC is the controlling element and the control surfaces are the elements being controlled.  When a pilot commends an action but the computer commands something else the pilot in command is not in command the way they may wish.  The computer has its say and while you could play semantics and say its ALONGSIDE versus in between the consequence is the same is it not.  The fact remains that even in a non-fly-by-wire AC the computer can take control and circumvent the intentions of the pilots. 

I'm not sure what's driving your semantic dispute but as far as I'm concerned this is what it is.  At low altitude if the computer puts the plane into a dive the pilots may not have enough time to turn off the system and recover.  Let's say the plane is at 5000 feet at 400 knots and the computer issues a trim command that puts the plane into a 30 degree dive -- without intervention they would be less than 17 seconds before impact.  They would have much less than that to react, turn off the system, and pull out of the 30 degree dive.  In fact, if the plane got to a 30 degree dive at 5000 feet it may already be too late and there would be nothing to prevent disaster even if they turned off the system, correctly, the instant that happened.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: amyk on November 15, 2018, 02:31:03 am
The trim wheels are also not small (intentionally so) and make a clicking racket when in motion (also intentional):
https://www.youtube.com/watch?v=cQirIH_DuAs (https://www.youtube.com/watch?v=cQirIH_DuAs)
Quote
do NOT attempt to stop it by putting your palm over a running wheel as this leads to a burn
:o I'm not a pilot but trying to grab hold of a rapidly and forcefully spinning object sounds rather dangerous and reminds me of lathe safety lessons... there's no disconnect mechanism?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 15, 2018, 02:50:46 am
The first means to stop runaway trim is auto-pilot disconnect (generally the biggest red switch on the outside yoke arm, easily accessible by your thumb).
The second means is by turning the switch off to the system.
The third means is to grab the metal wheel and force against the clutch that's driving it.

It's not especially dangerous and certainly is less dangerous than allowing a runaway trim condition to continue!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 15, 2018, 05:01:28 am

I'm not sure what's driving your semantic dispute but as far as I'm concerned this is what it is.  At low altitude if the computer puts the plane into a dive the pilots may not have enough time to turn off the system and recover.  Let's say the plane is at 5000 feet at 400 knots and the computer issues a trim command that puts the plane into a 30 degree dive -- without intervention they would be less than 17 seconds before impact.

The dispute, I think, comes from you not quite getting how flying feels. If the plane is flying on AP and your attention is elsewhere, yes, the computer can put the plane into a dive. (Though honestly, 17 seconds is a long time to grab the control right in front of you and arrest that dive -- though not too fast, you don't want an accelerated stall.)

But if your hands are on the controls, the computer cannot "put the plane into a dive." What it can do is trim the plane to dive, which you will immediately (as in before the attitude actually changes) perceive as a very unpleasant sudden nose heaviness. Every pilot knows what an uncommanded trim change feels like while flying. It doesn't feel good, it's a lizard brain muscle memory, and I think the vast majority of pilots would fight it immediately while simultaneously reaching for the trim controls.

The exception to this would be if the pilot was also getting stall warnings; then he might hesitate before pulling back. But in clear weather I think it would only be a few seconds before, looking at the aircraft's attitude and power settings, he could surmise that the aircraft wasn't actually near a stall.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 15, 2018, 05:15:10 am
... systems controlled by the computer that interpose themselves between the flight control surfaces and the pilot ...
You keep saying BETWEEN, trying to impose the definition of fly-by-wire on systems that aren't. The reality is ALONGSIDE; manual controls still work, and in most cases can overpower the automatics even if they are not switched off. The pilots are NOT disconnected from the control surfaces. Even with all the updates over decades, the 737 remains a very successful 1960's era design at the core.

The data recorder is going to have all we need to know about automatic vs manual inputs to the system, as well as what the instruments were saying at the time. It should also shoot down 95% of the speculation in this thread, once a decent analysis is released. But we really need that cockpit recorder to know what was going on in the heads of the pilots for those last 10 minutes.

However they got there, I'm guessing they ended up in an actual aerodynamic stall. Which, even when in full control, is likely not recoverable in the <5000 feet they had available. It fits the information we have so far. (For the benefit of the non-pilots, the way to regain control from a full stall is to enter a dive to regain airspeed, and then you have to recover from the dive. You lose a LOT of altitude in the process, very quickly.)

You're right, I'm not familiar with fly-by-hose where you have two hydraulic systems battling it out.
It's still not making sense from many perspectives.

If a pilot makes an error causing a stall and the MCAS tries to correct it yet still allows the pilot to override that, I'm not sure what the point is. An adamant pilot can still go into and stay in a stall condition, as flight 447 did.
Why are you needing to switch off power to the stab trim system if you can overrule it.

The AOA sensor had been replaced, so the airspeed sensor or something else must have been aggravating all this.

The cockpit voice recorder beacon (https://www.l3aviationproducts.com/products/90-day-beacon) looks like its rated for 90-day battery life and 1.8-3.6km range. 160dB chirp at 37.5kHz but buried under mud or debris. It would have many answers.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 15, 2018, 06:12:05 am
If a pilot makes an error causing a stall and the MCAS tries to correct it yet still allows the pilot to override that, I'm not sure what the point is.

The point is that the system has "told" the pilot something. The pilot can integrate that information in his picture of what is going on. He can let the automation do what it wants, or, if he believes he knows something the computer doesn't, he can fight it. That's the Boeing philosophy. The Airbus philosophy is that the pilot will need to take extraordinary steps (in advance) to override the aircraft.

I really do not think there is enough accident data out there these days to make a good assessment of which approach is safer overall. It's a very complex question because very sophisticated automation tend to de-skill operators, which becomes an acute problem in the few cases where the automation fails.

(such as An adamant pilot can still go into and stay in a stall condition, as flight 447 did.

But the A320 is an FBW aircraft, and so normally, a pilot could not stall it. But in this case, the computer had punted and dropped into "alternate law" where the not all the normal envelope protections were applied.

Why are you needing to switch off power to the stab trim system if you can overrule it.

Because you will tire of overruling it continuously. It takes physical and mental effort to fly an untrimmed aircraft, much less one that keeps trying to make itself  untrimmed.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 15, 2018, 08:11:28 am
Because it's not just semantics, especially when your primary argument is about what happens when computers misbehave.

In a fly-by-wire setup, if you lose all the flight control computers, you CANNOT fly the plane. The pilot controls are merely input devices to the computer, like a joystick, keyboard or mouse on a PC. No computer, no control. Turning them off is NOT an option if you want to live.

In the 737, while a lot of electronics are important, none of it is absolutely essential for flight. You can turn them all off and still have operating controls to fly the plane with.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 16, 2018, 01:41:01 am

I'm not sure what's driving your semantic dispute but as far as I'm concerned this is what it is.  At low altitude if the computer puts the plane into a dive the pilots may not have enough time to turn off the system and recover.  Let's say the plane is at 5000 feet at 400 knots and the computer issues a trim command that puts the plane into a 30 degree dive -- without intervention they would be less than 17 seconds before impact.

The dispute, I think, comes from you not quite getting how flying feels. If the plane is flying on AP and your attention is elsewhere, yes, the computer can put the plane into a dive. (Though honestly, 17 seconds is a long time to grab the control right in front of you and arrest that dive -- though not too fast, you don't want an accelerated stall.)

But if your hands are on the controls, the computer cannot "put the plane into a dive." What it can do is trim the plane to dive, which you will immediately (as in before the attitude actually changes) perceive as a very unpleasant sudden nose heaviness. Every pilot knows what an uncommanded trim change feels like while flying. It doesn't feel good, it's a lizard brain muscle memory, and I think the vast majority of pilots would fight it immediately while simultaneously reaching for the trim controls.

The exception to this would be if the pilot was also getting stall warnings; then he might hesitate before pulling back. But in clear weather I think it would only be a few seconds before, looking at the aircraft's attitude and power settings, he could surmise that the aircraft wasn't actually near a stall.


If the plane is in a 30 degree dive at 5000 feet you'd have less than 17 seconds if you did nothing.  However, disabling the trim then pulling out of the dive and doing that with 5000 feet to play with means you have less time than 17 seconds.  If you were heads down and didn't notice until the plane was 30 degrees down at 5000 feet its a good bet you would not be able to recover even if you acted with zero delay.  You don't arrest a 30 degree dive at 400+ knots without losing a fair bit of altitude.  Physics is a bitch!


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: alsetalokin4017 on November 16, 2018, 02:53:42 am
However, even the heads-down pilots will notice the bunt from level pitch to 30 degrees nose down. That's a negative g maneuver! Or if they have hands on the yoke (the suspect system allegedly only operates when manually flying) they will notice the sudden trim change as they have to apply considerable back pressure to prevent or recover from the bunt.
Physics is hard, but the ground is harder. Or in this case the water surface.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SiliconWizard on November 16, 2018, 03:49:52 am
In the AF447 scenario, the computer decided it did not have reliable air data, so it not only disconnected the autopilot, it dropped into alternate law. Basically, the computer just punted and said "your airplane!" This might seem like reasonable behavior, but one might imagine that handing a degraded airplane to a pilot at the very worst moment is not a satisfactory failure mode, and in the AF447 scenario the outcome was obviously bad.

This seems reasonable, and I still think it is. I don't think Airbus has changed this behavior after this tragedy (but don't hesitate to tell us if they did, as I may have missed the info), so a lot of people have probably considered it reasonable as well. The moment this happened, the plane was NOT in a critical situation whatsoever as far as I remember, so yes this was stressful and pilots got misled somehow, but they would have had ample time to handle this the right way. Turns out that the training on those airliners with a lot of automation don't always have enough simulation sessions for handling this kind of situations, and that's one of the things they improved after the accident: training sessions. The warning indicators are not always very clear either, and this surely could be improved, but at least in this case, they were certainly not lacking as there was a continuous stream of warnings including stall warnings IIRC. The main point as I remember is the pilots were not trusting ANY indication anymore, so obviously they lost all reference and situational awareness.

Again, if some automated system RELIES on some sensor data and this data is DETECTED as not reliable, the system should obviously be disconnected.
That said, if alternate systems that DONT need those sensor data can still be activated to make it safer, of course this could be a good idea to activate them. But keeping on a system that takes some of the controll OFF the hands of the pilots based on unreliable data is a recipe for disaster. That's all I'm saying here, and this is also what has been pointed out and suspected in this Lion Air case by some.

Very interested in reading the final report.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 16, 2018, 07:37:35 am
In the AF447 scenario, the computer decided it did not have reliable air data, so it not only disconnected the autopilot, it dropped into alternate law. Basically, the computer just punted and said "your airplane!"

This seems reasonable, and I still think it is. I don't think Airbus has changed this behavior after this tragedy (but don't hesitate to tell us if they did, as I may have missed the info), so a lot of people have probably considered it reasonable as well.

I'd say it was reasonable, but unfortunate. And yes, I think if you have a crew that was so deficient in basic airmanship, there's ultimately not much you can do to help folks who are going to do stupid things. Assuming all your instruments are wrong because some of your instruments are wrong is not just dumb in an Airbus, it is dumb in any airplane. You can go right back to your basic instrument training in piston single: you can get work out and bad air data from the remaining instruments. In turbulence, I'm sure it's scary and difficult, but if the pilots had simply flown an attitude and power setting, they would have been fine. I think there's not much doubt about that.

This is the final BAE report on AF447, translated in English: https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf (https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf)

(SiWizard, from your flag, I suspect this version will be more to your liking: https://www.bea.aero/docspa/2009/f-cp090601/pdf/f-cp090601.pdf (https://www.bea.aero/docspa/2009/f-cp090601/pdf/f-cp090601.pdf))


Section 5 lists the changes after the aircraft. Basically, other than improving the pitot heaters, I don't think any changes were made to the aircraft. Several training and flight manual changes were made, such as making sure pilots understand that they are not getting stall protection under alternate law.

Completely revamping the flight control software on an airliner that has been in production for a long time perhaps would be a bridge too far, and add additional risk. Furthermore, improving the pitot system so that you don't get a total loss of air data would certainly be a simpler option. I wonder how many times since AF447 an A320 has lost air data. Maybe none?

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 16, 2018, 06:36:41 pm
... systems controlled by the computer that interpose themselves between the flight control surfaces and the pilot ...
You keep saying BETWEEN, trying to impose the definition of fly-by-wire on systems that aren't. The reality is ALONGSIDE; manual controls still work, and in most cases can overpower the automatics even if they are not switched off. The pilots are NOT disconnected from the control surfaces. Even with all the updates over decades, the 737 remains a very successful 1960's era design at the core.

Multiple sources are saying the MCAS system cannot be overridden by the pilot, unless power is cut.
This seems counter to what many are saying about fly-by-hose/wire systems or Boeing's philosophy?

"Any pilot’s natural reaction when a plane’s nose begins to tilt down uncommanded is to pull back on the yoke and raise the nose. In normal flight mode, that would work, because pulling back on the yoke triggers breakout switches that stop any automatic tail movement tending to move the nose of the plane down.

But with the MCAS activated, said Fehrm, those breakout switches wouldn’t work. MCAS assumes the yoke is already aggressively pulled back and won’t allow further pullback to counter its action, which is to hold the nose down."

FAA evaluates a potential design flaw on Boeing’s 737 MAX after Lion Air crash (https://www.seattletimes.com/business/boeing-aerospace/faa-evaluates-a-potential-design-flaw-on-boeings-737-max-after-lion-air-crash/)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 16, 2018, 07:29:47 pm

Multiple sources are saying the MCAS system cannot be overridden by the pilot, unless power is cut.
This seems counter to what many are saying about fly-by-hose/wire systems or Boeing's philosophy?


Yes, it does certainly seem so based on this reporting. I think that's why former avionics engineers and a bunch of pilots are alarmed, especially if the behavior of the airplane has changed but the AFM doesn't reflect that change. It's subtle, I think. If you follow the procedure in the AFM to disable the trim system, it sounds like you're OK, but if you are relying on expectations that you can just pull back (as you have on all previous 737s), you'll get different behavior. Just speculating, but I'd bet the flight manual probably never said "just pull back until you can get the trim sorted," but perhaps pilots do exactly that, since in normal flight that works. I have no jet time, but in the much simpler aircraft I've flown, it's just what I would do. If the AP was doing something unusual, I would simultaneously disable the AP and use the primary controls first and then adjust trim to relieve control forces second.

But with the MCAS activated, said Fehrm, those breakout switches wouldn’t work. MCAS assumes the yoke is already aggressively pulled back and won’t allow further pullback to counter its action, which is to hold the nose down."

I'm a bit surprised the computer assumes anything about the position of the yoke. I'd have hoped it would know the position of the yoke. So, if the AOA sensor is saying one thing, but the position of the yoke and trim are not consistent with a stall, it might "think twice" about assuming a stall and forcing the nose down. But that might be a bit too much fuzzy reasoning to expect from a system like that.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 17, 2018, 03:17:07 am

Multiple sources are saying the MCAS system cannot be overridden by the pilot, unless power is cut.
This seems counter to what many are saying about fly-by-hose/wire systems or Boeing's philosophy?


Yes, it does certainly seem so based on this reporting. I think that's why former avionics engineers and a bunch of pilots are alarmed, especially if the behavior of the airplane has changed but the AFM doesn't reflect that change. It's subtle, I think. If you follow the procedure in the AFM to disable the trim system, it sounds like you're OK, but if you are relying on expectations that you can just pull back (as you have on all previous 737s), you'll get different behavior. Just speculating, but I'd bet the flight manual probably never said "just pull back until you can get the trim sorted," but perhaps pilots do exactly that, since in normal flight that works. I have no jet time, but in the much simpler aircraft I've flown, it's just what I would do. If the AP was doing something unusual, I would simultaneously disable the AP and use the primary controls first and then adjust trim to relieve control forces second.

But with the MCAS activated, said Fehrm, those breakout switches wouldn’t work. MCAS assumes the yoke is already aggressively pulled back and won’t allow further pullback to counter its action, which is to hold the nose down."

I'm a bit surprised the computer assumes anything about the position of the yoke. I'd have hoped it would know the position of the yoke. So, if the AOA sensor is saying one thing, but the position of the yoke and trim are not consistent with a stall, it might "think twice" about assuming a stall and forcing the nose down. But that might be a bit too much fuzzy reasoning to expect from a system like that.


And, if the pilots went with the 'pull back the stick option' as there first attempt at the altitude and airspeed they were at they would not have had time for option two -- this software system will have to be removed until a better thought out system can be implemented.  Boeing is going to eat this one and it will cost there insurer hundreds of millions I'd wager. 

The law of unintended consequences sometimes makes fools of your best plans.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on November 19, 2018, 01:12:50 am
https://www.youtube.com/watch?v=zfQW0upkVus (https://www.youtube.com/watch?v=zfQW0upkVus)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: maginnovision on November 19, 2018, 01:47:46 am
https://www.youtube.com/watch?v=zfQW0upkVus (https://www.youtube.com/watch?v=zfQW0upkVus)

The way he explains it makes it seem even worse than I thought. Potentially single failure combined with lack of training.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 20, 2018, 01:32:35 am
https://www.youtube.com/watch?v=zfQW0upkVus (https://www.youtube.com/watch?v=zfQW0upkVus)

I don't think there's much in this video that is different from what has been discussed on this thread so far. For now, I'm sticking with my "prediction" that the pilots and Boeing will end up with some of the responsibility. There's nothing here to imply that the aircraft could not be flown. It's definitely not okay that Boeing put in a new flight control system and made no mention of it in the  true-up training for the MAX. On the other hand, if that system started moving trim according to rules unknown to them, that would seem like the very definition of runaway trim to pilots who didn't know about MCAS, and if they followed the procedure for that, they would have been fine.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on November 20, 2018, 11:35:35 am
Lets say they used the thumb sticks to pull trim back and then took out the checklist because they assume they have corrected the problem for now and have some breathing room, so now they are distracted and then the system hits trim again after the time out. It's just such a fucking mess.

IMO they need a big red button to turn off autopilot, but really, actually, completely, not partially.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 20, 2018, 01:16:20 pm
It's a two-crew airplane for a reason. Pilot Flying (PF) does the memory items and calls for the checklist. Pilot Not Flying (PNF) pulls out the Quick Reference Handbook (QRH) and reads the checklist items in challenge form. PF responds with the response. The whole time PF keeps flying the airplane and monitoring its performance, including attitude and airspeed.

You don't have two people going heads-down into the books. (It happens, most notably, tragically, and avoidable in something in Eastern 401, where 101 people died because a cockpit crew of three mismanaged a burned out landing gear position indicator bulb. Since then, CRM classes have taught the division of duties to avoid future "two researchers, zero pilots" situations.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: daddylonglegs on November 20, 2018, 06:07:50 pm
If there is disagreement, it obviously doesn't matter which one is wrong to detect there is a malfunction. This case would warrant the disconnection of any automatic system that could rely on or even be influenced by those sensors, and issue a warning. First thing that happens is usually the disconnection of the autopilot, and I'm pretty sure that happens when there is a faulty pitot, at least on Airbus planes. This is the first thing that happened on the AF447 for instance, AFAIK. Of course, this could be different in this case. Maybe.

In the AF447 scenario, the computer decided it did not have reliable air data, so it not only disconnected the autopilot, it dropped into alternate law. Basically, the computer just punted and said "your airplane!" This might seem like reasonable behavior, but one might imagine that handing a degraded airplane to a pilot at the very worst moment is not a satisfactory failure mode, and in the AF447 scenario the outcome was obviously bad.


  ISTM that Airbus have made fairly clear and consistent design choices. The flight envelope protection will not allow the pilots to stall or overspeed the aircraft unless the sensors start playing up (in a detectable way) or the pilots deliberately disable this system (which takes a single action). Not everyone likes the choices but they are reasonable. I agree with you that it is difficult to make changes that are unambiguously better.

  Judging by the AD, the accretion of changes to the 737 has produced a system that is:
A - Badly documented (supposedly a deliberate choice to save time and money during training).
B - Does not completely handover control when the sensors disagree (even warning the pilots that the sensors are playing up is an optional extra! [1]).
C - Requires two actions, both disabling the autopilot and cutting out the trimming system.

  I think Boeing have been caught out by the compromises involve in updating a very old design[2], marketing pressures[3] and - possibly - by their own propaganda regarding how traditional the flight controls on a Boeing are. My predictions are that:
A - Training will now heavily cover the auto trim systems.
B - The sensor disagreement warning will not be optional in practice (everyone will buy it)
C - Boeing may have to change the MCAS system by adding a cut-out when the sensors disagree (should have done that from the start IMHO).

  I'm surprised at what is hidden from pilots both in the manuals and by making the sensor warnings optional. If pilots get a stall warning without an explicit indication that the sensors disagree[4] they may well believe it. Particularly if they have already been surprised by changes in the aircraft's motion (driven by the automated system's intervention) and so lost their 'feel' for whether the aircraft might plausibly be close to stalling. A curious and sad inversion of the AF447 crash if so.

  All of this is my ill-informed opinion. Both Airbii and Boeings are flown very safely by sensible airlines. The Lion Air crash may well be something completely different, etc.

[1] Maybe Boeing could consider in-appflight purchases in this case? "We've noticed that your subscription does not include information helpful to your continued survival. Would you like to upgrade? (T&C apply. Always make sure you have the permission of the credit card holder. Offer not valid if you're going to sue us.)"

[2] First flight in 1967, 51 years ago and 64 years after the Wright brothers. Dates from wonkypedia, maths from my sligtly tired brain.

[3] Honestly, I get infuriated by manufacturers making an oscilloscope's actual capabilities an optional (i.e. expensive) upgrade and now Boeing's marketing department gets in on the game? And then nobbles the flight manual/ conversion course to boot?

[4] Do any of the checklists (memory or written) call for comparing the instruments?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 20, 2018, 06:22:32 pm
C - Requires two actions, both disabling the autopilot and cutting out the trimming system.
This is standard. My 3600-pound airplane has the same basic response for an AP or electric trim malfunction. My previous 2800-pound airplane didn't have electric trim installed, but if it did, it would have been the same.
[4] Do any of the checklists (memory or written) call for comparing the instruments?
This is the fundamental skill of all instrument-rated pilots and a primary focus of instrument flight instruction.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 20, 2018, 06:55:55 pm
https://www.youtube.com/watch?v=zfQW0upkVus (https://www.youtube.com/watch?v=zfQW0upkVus)

I don't think there's much in this video that is different from what has been discussed on this thread so far. For now, I'm sticking with my "prediction" that the pilots and Boeing will end up with some of the responsibility. There's nothing here to imply that the aircraft could not be flown. It's definitely not okay that Boeing put in a new flight control system and made no mention of it in the  true-up training for the MAX. On the other hand, if that system started moving trim according to rules unknown to them, that would seem like the very definition of runaway trim to pilots who didn't know about MCAS, and if they followed the procedure for that, they would have been fine.


Umm, no...

If this runaway trim happened at 5000 feet and they spent even a few seconds fighting the stick by the time they did turn things off the plane would be at 3000 feet and 30 degrees down -- you won't recover from that even with the trim system turned off.

The idea that pilots will automatically and with zero delay jump to a seldom used (or never used) emergency procedure is delusional -- that's not how humans respond.  They will attempt to pull back on the stick and then, maybe, realize they need to turn the trim off but by then...


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 20, 2018, 07:04:20 pm
You have to manually crank the stabilizers back to center, after shutting off power to the motors.
Can you imagine how hard that is, it's two BLDC with screw-jack and you don't have much time.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 20, 2018, 07:24:46 pm

If this runaway trim happened at 5000 feet and they spent even a few seconds fighting the stick by the time they did turn things off the plane would be at 300 feet and 30 degrees down -- you won't recover from that even with the trim system turned off.

The idea that pilots will automatically and with zero delay jump to a seldom used (or never used) emergency procedure is delusional -- that's not how humans respond.  They will attempt to pull back on the stick and then, maybe, realize they need to turn the trim off but by then...

I think neither of us are airline pilots, so we'll just have to disagree about this and find out what's in the reports when they come out. My sense as a pilot (not an airline pilot) is that this is EXACTLY the kind of thing that is -- or should be -- on a pilot's mind, particularly when climbing out at low altitude. As I've said before, these trim changes, though fast, are not instantaneous. They can be felt. Furthermore, a sudden trim change doesn't result in an instantaneous attitude change. (The plane has a moment of inertia and it takes time for the nose to rotate down). And an instantaneous attitude change does not result in an instantaneous altitude change. Some of these delays work against you as you try to arrest a descent just as they work for you at the start of the descent, but I'm nearly certain that proficient, attentive pilots can recovery from a runaway trim situation that starts at 5000 feet.

Yes, if you get into a 6000 fpm minute descent then you are probably screwed, but you'd really have to let the plane get into a seriously unusual attitude to get that kind of descent.

It may seem as if a few armchair pilots are being perhaps a bit too harsh on the pilots in this scenario -- and I'm willing to concede that maybe we are. But you have to understand that pilots are always supposed to be thinking of what can go wrong in each phase of flight and what they'd do about it. It's the essence of piloting. Flying a working airplane is not particularly hard. Managing a "normal" flight takes up a surprisingly small fraction of overall flight training. Most flight training is about handling abnormal situations, and dealing with those is the crux of a pilot's job. Cross checking instruments (including checking them against the huge non-artificial horizon available in VMC) and avoid and recovering from unusual attitudes are definitely in this category.


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rx8pilot on November 20, 2018, 07:47:58 pm
You have to manually crank the stabilizers back to center, after shutting off power to the motors.
Can you imagine how hard that is, it's two BLDC with screw-jack and you don't have much time.

Pretty sure it is somewhere between 'very hard' and 'impossible' once the system has gone full nose heavy. In a manual operation, it is a LOT of turns and needs considerable effort to move. All of that has to be accomplished in the middle of a very confusing and scary emergency event that is very rapidly getting worse. There is little doubt that both pilots knew it was a deadly situation early on which would make rational decision making that much harder.

The speculation will slowly give way to actual facts.....but it is looking like the pilots would need to be superhuman to have avoided the outcome.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 20, 2018, 08:32:51 pm
Pretty sure it is somewhere between 'very hard' and 'impossible' once the system has gone full nose heavy. In a manual operation, it is a LOT of turns and needs considerable effort to move
This is true, but they struggled with the airplane for quite some number of minutes. It's during this time, before the stab trim runs full nose-down, that was the time to interrupt the power to the trim system.

They were dealt a crap hand to be sure. I'm much less sure that a majority of 737 pilots would fall victim to that crap hand. I think the CVR will be enlightening to understand what was going on in their heads as they fought the airplane. The FDR and wreckage can tell us a lot of the WHAT; the CVR will help with the WHY.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 21, 2018, 08:01:14 pm
As is common in major tragedies the end result stems from more than one problem.  If the stab ran-away as a singular event I'd guess they would have responded as they should and they would still be alive.  However, going back over time to the 3 previous flights, which the pilots must have been aware of, the thing of concern appears to have been BOTH a pitot/static problem and an AOA problem.  So, on the day of the crash there first indications may well have been in line with what the previous pilots reported and they were very likely working that problem when the stab trim system threw them for a loop -- a stab trim system they did not fully understand because Boeing neglected to provide that information.

When you're working one or two known problems and a third rears its head you can bet there was a period of seconds at least where they tried to correlate the new problem with the existing ones.  At 5000 feet they don't have that time.  And, as other suggest, once the system threw the plane into a nose down attitude with, potentially, substantial down trim, they would have to manually rotate the trim wheels which, again, at 5000 feet they would have very little time.

This has the makings of a horror story!


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 22, 2018, 09:01:08 pm
The video from the Mentor pilot about the MCAS system provides some interesting info about what may have necessitated the MCAS system.  The 737MAX uses larger more fuel efficient engines but do to the low ground clearance of the basic 737 design they need to mount the engine further forward and up to gain some clearance.  Doing that would have changed the balance of the AC meaning that all things being equal it would need the stabilizer to be trimmed up more than previous 737 AC for a given flight condition.  It's not clear to me if there were any other changes to compensate for the changed balance or if the stabilizer was changed in some way, but his mention of the larger engine and the need to alter the mounting location certainly raises some questions in my mind.  In a perfect world such an alteration would necessitate other changes to return the balance -- perhaps moving some gear further aft, perhaps moving some of the fuel tanks further aft, perhaps altering the stabilizer to account for what would otherwise be a nose heavy tendency. 

We are likely to see an interim report within a couple weeks but the FAA and Boeing probably know already exactly what happened.  Hopefully the interim report provides some closure on this.  OTH, if the engine change started a chain of other changes that lead to this Boeing could have bigger problems than the legal one they are no doubt going to face.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 23, 2018, 01:10:51 pm
I think folks here are ignoring some key facts. First, that the emergency bulletin from Boeing does nothing but explain MCAS behavior and amplify existing procedures. Second, that the -MAX aircraft are still in service.

This strongly suggests that the aircraft are believed safe by Boeing and the FAA and that at least for the interim, the only extra training pilots need is a reminder not to let the plane get way out of trim.

I find the points that the pilots were screwed once the plane was way out of trim to be mostly irrelevant. Yes, there may not be time to recover by manually re-trimming a plane that is totally nose heavy at low altitude. That's why you don't let the aircraft into that condition. There are many conditions that you can get into that are not recoverable. You just don't let the aircraft get there.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 23, 2018, 07:42:51 pm
I think folks here are ignoring some key facts. First, that the emergency bulletin from Boeing does nothing but explain MCAS behavior and amplify existing procedures. Second, that the -MAX aircraft are still in service.

This strongly suggests that the aircraft are believed safe by Boeing and the FAA and that at least for the interim, the only extra training pilots need is a reminder not to let the plane get way out of trim.

I find the points that the pilots were screwed once the plane was way out of trim to be mostly irrelevant. Yes, there may not be time to recover by manually re-trimming a plane that is totally nose heavy at low altitude. That's why you don't let the aircraft into that condition. There are many conditions that you can get into that are not recoverable. You just don't let the aircraft get there.


You are presupposing that the pilots chose to remain at low altitude when in a normal climb-out they would have been much higher at 13 minutes.  The flight profile shows a lot of erratic up and down which I should point out is not typical of a normal climb-out. 

So, it looks to me that the plane was at a dangerously low altitude and when the final push happened, or whatever the final event was, they were too low to recover even if they had the control authority to do so which is highly suspect at this point.  The emergency bulletin from the FAA and the technical bulletin from Boeing would hardly be considered business as usual.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 23, 2018, 09:17:39 pm
Actually, such alerts probably are business as usual when pilots point out a safety/training deficiency.

Until we get more info, it's just speculation that it had anything to do with the crash.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 26, 2018, 11:05:49 pm
Actually, such alerts probably are business as usual when pilots point out a safety/training deficiency.

Until we get more info, it's just speculation that it had anything to do with the crash.


The FAA seldom uses the word "Emergency" to issue nothing out of the ordinary messages. 

We should see the interim report in a few days and have a better idea of what is fact and what has been speculation.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 27, 2018, 03:07:31 am
Actually, such alerts probably are business as usual when pilots point out a safety/training deficiency.

Until we get more info, it's just speculation that it had anything to do with the crash.


The FAA seldom uses the word "Emergency" to issue nothing out of the ordinary messages. 

We should see the interim report in a few days and have a better idea of what is fact and what has been speculation.


Brian
You missed my point. Issuing Airworthiness Directives is simply one of the things the FAA does. That includes emergency ones, of which you'll find at least a handful every year, sometimes more. They're just doing their job. It's not unusual when deciding what qualifies as an emergency is normal procedure, so it's business as usual.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 27, 2018, 04:53:22 am
I think folks here are ignoring some key facts. First, that the emergency bulletin from Boeing does nothing but explain MCAS behavior and amplify existing procedures. Second, that the -MAX aircraft are still in service.

This strongly suggests that the aircraft are believed safe by Boeing and the FAA and that at least for the interim, the only extra training pilots need is a reminder not to let the plane get way out of trim.

I find the points that the pilots were screwed once the plane was way out of trim to be mostly irrelevant. Yes, there may not be time to recover by manually re-trimming a plane that is totally nose heavy at low altitude. That's why you don't let the aircraft into that condition. There are many conditions that you can get into that are not recoverable. You just don't let the aircraft get there.

You are presupposing that the pilots chose to remain at low altitude when in a normal climb-out they would have been much higher at 13 minutes.  The flight profile shows a lot of erratic up and down which I should point out is not typical of a normal climb-out. 

So, it looks to me that the plane was at a dangerously low altitude and when the final push happened, or whatever the final event was, they were too low to recover even if they had the control authority to do so which is highly suspect at this point.  The emergency bulletin from the FAA and the technical bulletin from Boeing would hardly be considered business as usual.


Brian

I'm trying to reason based on clearly stated suppositions -- none of which require that the pilots "chose to remain at low altitude."

- It is a fact that the aircraft are still in service.
- It is arguably a fact that Boeing and the FAA are extremely risk-averse. Certainly, the repercussions for another crash due to the same or a related problem would be severe.

This strongly suggests that the model is safely flyable, including under all but the most improbably failure circumstances. It also suggests that a "design fault" is not the proximate cause of this accident.

If that is true, then either:

 - the accident aircraft was "broke" in some very unlikely way
 OR
 - the operator of the accident aircraft conducted maintenance malpractice and sent an unairworthy aircraft into service
 OR
 - the pilots screwed up
 OR
 - some combination of the above


As for why the pilots maneuvered at low altitude, we simply do not know.

As others have stated before, accidents do have multiple causes, and I expect this one will, too.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 27, 2018, 05:26:34 am
The root cause, the AOA or air speed sensor issue I don't think has been figured out. Another airline, Southwest had replaced a couple of AOA sensors on their 737 MAX 8's.

The problem looks like it was intermittent, on and off. Previous flights had the same problem, sensor was replaced etc.
Air Asia Crash Report : Cracked Solder Joint on Rudder Limit Circuit Board https://www.eevblog.com/forum/chat/air-asia-crash-report-cracked-solder-joint-on-rudder-limit-circuit-board/ (https://www.eevblog.com/forum/chat/air-asia-crash-report-cracked-solder-joint-on-rudder-limit-circuit-board/)

How MCAS resolves a discrepancy when you only have two sensors that can (normally) read different, it's like the redundancy engineering is shit (=not there) and the pilot is expected to cover for it.

Boeing has a backlog of 4,783 orders (https://en.wikipedia.org/wiki/List_of_Boeing_737_MAX_orders_and_deliveries) for 737 MAX. for multi-billions $. I hope they don't put all this on the flight crew.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 27, 2018, 06:03:56 am
I hope they don't put all this on the flight crew.
I hope they put the blame on wherever the right place for the blame to go is.
If that's on the crew, so be it...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 27, 2018, 06:55:00 am
Actually, such alerts probably are business as usual when pilots point out a safety/training deficiency.

Until we get more info, it's just speculation that it had anything to do with the crash.


The FAA seldom uses the word "Emergency" to issue nothing out of the ordinary messages. 

We should see the interim report in a few days and have a better idea of what is fact and what has been speculation.


Brian
You missed my point. Issuing Airworthiness Directives is simply one of the things the FAA does. That includes emergency ones, of which you'll find at least a handful every year, sometimes more. They're just doing their job. It's not unusual when deciding what qualifies as an emergency is normal procedure, so it's business as usual.

Well of course the FAA issues emergency reports with some frequency, there are hundreds of different AC each with issues that rare there head from time to time.  FDR, like all US presidents, addresses Congress and on December 8th 1941 he did so again -- I would not describe his speech on that day as 'business as usual' even though numerous other presidents have made similar speeches.  The circumstances that preceded his speech made it something of an emergency.

When the FAA issues an emergency directive its because something time critical makes it an emergency so postponing the directive isn't acceptable.  When FDR declared war on Japan it wasn't business as usual even though doing so was the job of the president.

The terms 'business as usual' and 'emergency' or not synonymous -- they are in fact incongruous.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on November 27, 2018, 02:51:26 pm
Actually, such alerts probably are business as usual when pilots point out a safety/training deficiency.

Until we get more info, it's just speculation that it had anything to do with the crash.


The FAA seldom uses the word "Emergency" to issue nothing out of the ordinary messages. 

We should see the interim report in a few days and have a better idea of what is fact and what has been speculation.


Brian
You missed my point. Issuing Airworthiness Directives is simply one of the things the FAA does. That includes emergency ones, of which you'll find at least a handful every year, sometimes more. They're just doing their job. It's not unusual when deciding what qualifies as an emergency is normal procedure, so it's business as usual.

Well of course the FAA issues emergency reports with some frequency, there are hundreds of different AC each with issues that rare there head from time to time.  FDR, like all US presidents, addresses Congress and on December 8th 1941 he did so again -- I would not describe his speech on that day as 'business as usual' even though numerous other presidents have made similar speeches.  The circumstances that preceded his speech made it something of an emergency.

When the FAA issues an emergency directive its because something time critical makes it an emergency so postponing the directive isn't acceptable.  When FDR declared war on Japan it wasn't business as usual even though doing so was the job of the president.

The terms 'business as usual' and 'emergency' or not synonymous -- they are in fact incongruous.


Brian

Tell that to a 911 dispatch service, where every call is an emergency, by definition, until determined otherwise. They decide which calls are real emergencys many times an hour, and also the type of emergency....and it's still business as usual FOR THEM.

This FAA directive does not compare to an FDR declaration of war at all, which I do agree was a fairly unique event. It doesn't even describe anything wrong with an aircraft. All it demands are a few updates to training manuals in reaction to information put out by Boeing. I still call that business as usual FOR THE FAA. They determined the information was sufficiently urgent and reacted like they're supposed to.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 28, 2018, 01:25:23 am
From https://www.nytimes.com/2018/11/27/world/asia/indonesia-lion-air-crash-.html (https://www.nytimes.com/2018/11/27/world/asia/indonesia-lion-air-crash-.html)

Quote
"""
The information from the flight data recorder, contained in a preliminary report prepared by Indonesian crash investigators and scheduled to be released Wednesday, documents a fatal tug-of-war between man and machine, with the plane’s nose forced dangerously downward over two dozen times during the 11-minute flight. The pilots managed to pull the nose back up over and over until finally losing control, leaving the plane, Lion Air Flight 610, to plummet into the ocean at 450 miles per hour, killing all 189 people on board.
"""

Eleven Minutes.

Two dozen attempts.

Sorry, there's no way these pilots did not screw up. Again, that's not to say that the undocumented MCAS system and potentially erratic behavior from potentially bad air data are not factors. But these pilots most definitely screwed up.

Also:

Quote
"""
Despite Boeing’s insistence that the proper procedures were in the handbook, also called the emergency checklist, pilots have said since the accident that Boeing had not been clear about one potentially vital difference between the system on the new 737s and the older models. In the older versions, pilots could help address the problem of the nose being forced down improperly — a situation known as “runaway stabilizer trim” — by pulling back on the control column in front of them, the pilots say.

Family members grieving after police handed over the remains of their relatives who had been aboard Lion Air Flight 610.CreditEd Wray/Getty Images
In the latest 737 generation, called the Max, that measure does not work, they said, citing information they have received since the crash. The pilots on Lion Air Flight 610 appear to have forcefully pulled back on their control columns to no avail, before the final dive, according to the information from the flight data recorder.

Capt. Dennis Tajer, spokesman for the American Airlines pilot union and a 737 pilot, said he could not comment on any aspect of the investigation. But, he said, “in the previous model of the 737, pulling back on the control column, Boeing says will stop a stabilizer runaway.”

Information provided to American Airlines from Boeing since the crash, Captain Tajer said, “specifically says that pulling back on the control column in the Max will not stop the runaway if M.C.A.S. is triggered. That is an important difference to know.”

Boeing said in its statement on Tuesday that the existing procedures covered the latest 737 model.
"""


This strongly hints at something I suggested earlier, that the written procedures, when followed, work, but that 737 pilots may have been accustomed to another procedure (pulling back on the control column) that was never the official book procedure, but which also worked on all 737's until the -MAX.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 28, 2018, 08:05:20 am
Two dozen attempts -
It's an automatic system switching in and out, doing retries on its own, and possibly operating with bad noisy sensor data.

You have at least four oscillators. The MCAS software, the sensor(s), the pilot, the co-pilot.
The airplane or the pilot as the ultimate authority is yet another conflict.

Investigators are saying the plane was not airworthy. It should have been grounded as soon as problems surfaced on the previous flight.
One AOA sensor had been replaced, but still a 20 degree discrepancy.

Really need the CVR to figure out all that happened.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on November 28, 2018, 08:23:00 am
Yeah it seams to me like the pilots could have easily prevented the crash if they knew what to do, even if they spent a while to diagnose the problem.

But that's not to say they are completely at fault. The finger pointing should instead be focused more towards the training the pilots ware given. Clearly they should have known about such a significant system on the aircraft.

And this doesn't just mean hammering a bunch of step by step procedures into there head on what to do if something goes wrong. They should understand why each step of the procedure is on the list and how it interacts with the problem. Yes there need to be defined procedures for dealing with faults, but in the event that the procedure does not work (Such as a fault they did not foresee) or there are multiple interacting faults that render the procedure useless they shouldn't just be repeating the procedure over and over because that's all they know to do. They should instead start thinking about why the procedure did not help and try other things.

Tho in this case the pilots surely should have noticed the big noisy trim wheels spinning all the time. If the aircraft is pitching down and trim wheels are moving that should have been an instant association of it being a trim problem. You don't need to look trough a manual for a troubleshooting procedure if you can see where the problem is. Fix it quickly and then try to figure out why it happened so that you can make a decision if its safe to continue flying to the destination.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on November 28, 2018, 08:27:14 am
Well it looks as if there is some progress in not making the poor pilots the scapegoats....

Quote
Indonesian investigators have said the Lion Air plane that crashed last month killing 189 people was not airworthy and should have been grounded.


https://www.bbc.co.uk/news/world-asia-46121127 (https://www.bbc.co.uk/news/world-asia-46121127)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 28, 2018, 08:53:23 am
It looks like there were similar problems on previous flights and the PIC of the previous flight eventually turned off the trim system after, I think, the third round of AND (automatic nose down) commands from the computer.  So, the PIC on the previous flight appears to have done what needed to be done but the crew on the doomed flight did not.

It's also clear that there were more than one problem with airspeed and altitude as well as AOA readings being wrong. 

One truly scary thing is that even the previous flight that landed safely the PIC's stick shaker was on almost the entire flight -- that had to be unnerving.  Page 14 of the preliminary report shows some graphs of a few of the relevant data items during the 13 minute flight and you can see the near constant sequencing of the AND commands and the near constant manual nose up commands from the pilots and this continues all the way till the end.  I'd like to know if the AND commands would still show up even of the system were turned off, I suspect they would not and that would tend to confirm they never turned it off.

By my estimate reading the charts it took less than 20 seconds for the plane to depart the flight altitude and impact the ground.  Also interesting is the fact than during the final approximately 45 seconds the pitch trim position, which was a battle between the computer issued AND commands and the pilots manual pitch up commands, shows the computer continuing to issue the AND commands and the pilots continuing to issue manual nose up commands but in that final 45 seconds it doesn't look like the pilots commands had any effect.  So, for about 25 seconds of that final battle the AC pitched down a bit and lost a little altitude, but in the final 20 seconds the AC pitched down more noticeably, the altitude dropped more quickly, and the airspeed increased.

The graph from the previous flight is more compressed in time owing to the much longer flight but it appears the crew fought with the computer for about 20 minutes and then there doesn't seem to be any AND commands for over an hour which kind of suggests that with the trim system turned off there are no AND commands.

So, at this point we have:

1.   Numerous instrument issues covering several flights involving altitude, airspeed and AOA indications on the PIC (left) side -- this should have been fixed and confirmed fixed before passengers were allowed to fly on it
2.   The previous flight reported much the same problems and issued a PAN-PAN but continued the flight after turning off the trim system -- this should have been a PAN-PAN without the option to cancel
3.   The pilots of the doomed flight did not turn off the trim system and lost the fight at the end -- the pilots will get significant blame and that appears warranted
4.   The maintenance activities appear to suggest the techs relied on computer self tests which seemed to indicate no problems and its not clear what level of physical inspections were done -- did they do a leak test of the pitot static lines or not
5.   How was the AOA transmitter installed and does it have a registration pin or other mechanism to make sure it's installed at the right angle -- it not how did the techs set the angle on installation


Brian


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on November 28, 2018, 09:00:30 am
3.   The pilots of the doomed flight did not turn off the trim system and lost the fight at the end -- the pilots will get significant blame and that appears warranted
Unless:
The airline is shown not to have provided sufficient documentation or training on how to fully manage this new MCAS flight system.
 :popcorn:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on November 28, 2018, 09:12:52 am
Well it looks as if there is some progress in not making the poor pilots the scapegoats....

Quote
Indonesian investigators have said the Lion Air plane that crashed last month killing 189 people was not airworthy and should have been grounded.


https://www.bbc.co.uk/news/world-asia-46121127 (https://www.bbc.co.uk/news/world-asia-46121127)


Therefore, the pilots should never have been placed in that position in the first place!

It seems to me that this thread has taken an distasteful turn towards establishing the guilt of the pilots, prior to the issuing of the full report.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sokoloff on November 28, 2018, 12:30:41 pm
2.   The previous flight reported much the same problems and issued a PAN-PAN but continued the flight after turning off the trim system -- this should have been a PAN-PAN without the option to cancel
From a systems design standpoint, it is undesirable to create one-way doors IMO. If you make it impossible to cancel an urgency or emergency declaration, you increase the cognitive decision-making hurdle for a human to make that declaration. Aircraft and passengers have been lost from crews not declaring emergencies or otherwise clearly communicating the danger the flight was in. (Avianca 52 is the first one that comes to most people's mind, but there are others.)

There is already some resistance in non-commercial pilot community to declaring an emergency when it seems warranted. (There's another fairly vocal sub-group who argues against this position; I find myself in that group at times.) Pilots fear repercussions, paperwork, an investigation that might turn up something unrelated, etc. It's why the Aviation Safety Reporting System (https://asrs.arc.nasa.gov/) is not run by the FAA and provides immunity to crews, mechanics, and other license-holders, etc. I don't fly professionally, but I can only imagine that the pressure to not lose your job makes rule-following even more high stakes.

IMO, there's good reason for the pilot in command to be the final authority as to the conduct of the flight and would argue against taking that authority and responsibility away in normal ops, abnormal ops, or emergencies.
https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1949761/#msg1949761 (https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1949761/#msg1949761)

I want my pilots to be thinking "Aviate, Navigate, Communicate" (in that order of priority). I don't want "Litigate" to be on their minds at all; that can all be done at 0' AGL and 0 knots airspeed.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on November 28, 2018, 07:01:30 pm
2.   The previous flight reported much the same problems and issued a PAN-PAN but continued the flight after turning off the trim system -- this should have been a PAN-PAN without the option to cancel
From a systems design standpoint, it is undesirable to create one-way doors IMO. If you make it impossible to cancel an urgency or emergency declaration, you increase the cognitive decision-making hurdle for a human to make that declaration. Aircraft and passengers have been lost from crews not declaring emergencies or otherwise clearly communicating the danger the flight was in. (Avianca 52 is the first one that comes to most people's mind, but there are others.)

There is already some resistance in non-commercial pilot community to declaring an emergency when it seems warranted. (There's another fairly vocal sub-group who argues against this position; I find myself in that group at times.) Pilots fear repercussions, paperwork, an investigation that might turn up something unrelated, etc. It's why the Aviation Safety Reporting System (https://asrs.arc.nasa.gov/) is not run by the FAA and provides immunity to crews, mechanics, and other license-holders, etc. I don't fly professionally, but I can only imagine that the pressure to not lose your job makes rule-following even more high stakes.

IMO, there's good reason for the pilot in command to be the final authority as to the conduct of the flight and would argue against taking that authority and responsibility away in normal ops, abnormal ops, or emergencies.
https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1949761/#msg1949761 (https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg1949761/#msg1949761)

I want my pilots to be thinking "Aviate, Navigate, Communicate" (in that order of priority). I don't want "Litigate" to be on their minds at all; that can all be done at 0' AGL and 0 knots airspeed.


Yes, that is the dilemma and I know of no easy solution to it.  Pilots a reticent to delay or cancel a flight for maintenance issues do to pressure from the airline to stay on schedule so they tend to fly even when conditions should dictate they not fly.  You are quite right that having no choice in returning when a PAN-PAN is called might make it less likely they will call in one when deserved -- a kind of catch 22.  If this were an isolated event that would be one thing, but given the previous flights with similar issues I think this escalates the problem.  We are now seeing people in the aviation community stating publicly that this plane was not air worthy and I would agree with that.

As to the comment that we are being too quick to lay blame on the pilots, well, they should have known to turn of the stab trim system which suggests to me the pilots had an inadequate understanding of the flight controls and that's not acceptable for a commercial pilot, even a junior one.   To be sure, the failure to clarify the difference between the 737MAX and previous versions with respect to MCAS has to be seen as a contributing factor here.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 28, 2018, 07:46:09 pm
Two dozen attempts -
It's an automatic system switching in and out, doing retries on its own, and possibly operating with bad noisy sensor data.

You have at least four oscillators. The MCAS software, the sensor(s), the pilot, the co-pilot.
The airplane or the pilot as the ultimate authority is yet another conflict.

You will note from the QRH handbook page I posted earlier that there is nothing there about "turn the system back on and see if it does it again." You don't re-enable a dodgy flight control system. You just don't.
 
Investigators are saying the plane was not airworthy. It should have been grounded as soon as problems surfaced on the previous flight.
One AOA sensor had been replaced, but still a 20 degree discrepancy.

And nobody here is disagreeing with that.

"Airworthy" has a specific, technical legal meaning, and it is not "plane could not be flown." In highly colloquial language it means "the plane should not be flown." It's a huge difference. For example, if an engine fails in flight, the aircraft is obviously not airworthy, but it can still be flown and landed safely.

I have never said that the airplane was airworthy, or that there is nothing wrong with the MCAS by designed or (lack of) training. I have said that the pilots crashed a plane that unless we learn something new and very strange (like the cutout switches didn't work) could have been landed.

Accidents have multiple causes, and one of those causes is the pilots not following procedures.

Really need the CVR to figure out all that happened.

CVRs are very useful, but are only one clue among many that investigators use to determine the cause of accidents. Few GA aircraft have CVRs (or FDRs, for that matter) and yet the US NTSB routinely determines proximate and contributing causes to the vast majority of air crashes in the US. Searchable database is here https://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx (https://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx) and always fascinating reading.


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 28, 2018, 09:05:52 pm
We don't know the malfunctions the plane experienced.

An intermittent, something cutting in and out can confuse anyone as to what is working properly or not.
Simply switching off the trim motors leaves the stabilizer actuator where it last was- presumably set at nose down. Maybe it was switched back on to get the motors to move it back, if the sensor data smartened up. Maybe they couldn't manually crank them back in time.

Human psychology is to "blame the victim" and the pilot had 6,000hrs and co-pilot 5,000hrs so they may not have been inept. Boeing certainly is.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 28, 2018, 10:12:45 pm
An intermittent, something cutting in and out can confuse anyone as to what is working properly or not.

These guys weren't anyone, they were airline pilots. Furthermore, as has been discussed here ad nauseum, you don't need to know what is working properly or not to get out of this situation. You need to follow the book procedures. (Aside: it turns out that the QRH procedures for runaway stab are also memory items.)

Plenty of airliners have been lost from crews trying to debug something that should have been switched off or ignored.

Simply switching off the trim motors leaves the stabilizer actuator where it last was- presumably set at nose down. Maybe it was switched back on to get the motors to move it back, if the sensor data smartened up. Maybe they couldn't manually crank them back in time.

As has already been shown, there was a lot of time, and there was a significant period of more or less level flight. It will be interesting to know if in that period they could have climbed.

(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=583076)

Human psychology is to "blame the victim" and the pilot had 6,000hrs and co-pilot 5,000hrs so they may not have been inept.

This is not an argument.

Boeing certainly is.

Wait, what?

Human psychology is a lot of things, like a desire to be contrarian, or to defer to experts, or not to defer to experts, or to blame big companies, or not wanting to admit that airlines pilots might be fallible, or that 6000 hours of experience can go by without much in the way of experiences.

I think portraying the pilots as victims "before we know what happened" is also probably premature.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on November 29, 2018, 01:41:50 am
http://avherald.com/h?article=4bf90724/0008&opt=0 (http://avherald.com/h?article=4bf90724/0008&opt=0)

https://www.youtube.com/watch?v=1sZfeFJ9n0I (https://www.youtube.com/watch?v=1sZfeFJ9n0I)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on November 29, 2018, 06:42:14 am
Reading the Preliminary Report, previous flight did OK:
"Airspeed unreliable and alt disagree shown after take off. STS was also running to the wrong direction, suspected because of speed difference. Identified that CAPT instrument was unreliable and handover control to FO. Continue NNC of Airspeed Unreliable and ALT disagree."

"... the airline confirmed one of their maintenance engineers was on board of the aircraft during the accident flight. This was an "anticipatory measure" in the event of technical problems with the new aircraft."

A third opinion who may have added confusion or given wrong instructions or flipped a breaker.


I'm of the view Boeing has blood on their hands for the engineering.
One of the many questions put forth to the FAA by The Aviation Herald (http://avherald.com/h?article=4bf90724/0008&opt=0):

- Why was the MCAS permitted to operate on the base of a single AoA value showing too high angle of attacks? Why does the MCAS not consider the other AoA value?

This is a failure of the software algorithm and fault tree analysis. Can't think of one reason to keep the robot going. AoA also seems to feed corrections to airspeed and altitude.

The forum poster, about knowing to shut off a system you don't even know about:
"As a captain on Boeing 737, I feel betrayed about Boeing's statements about their documentation. Even as of now, the MCAS has not been incorporated into the FCOM, nor into the FCTM. Their press release is a shameless lie."
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: mrpackethead on November 29, 2018, 08:14:03 am


https://www.youtube.com/watch?v=zfQW0upkVus (https://www.youtube.com/watch?v=zfQW0upkVus)

https://www.youtube.com/watch?v=1sZfeFJ9n0I (https://www.youtube.com/watch?v=1sZfeFJ9n0I)

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on November 29, 2018, 04:16:34 pm
Reading the Preliminary Report, previous flight did OK:
"Airspeed unreliable and alt disagree shown after take off. STS was also running to the wrong direction, suspected because of speed difference. Identified that CAPT instrument was unreliable and handover control to FO. Continue NNC of Airspeed Unreliable and ALT disagree."

"... the airline confirmed one of their maintenance engineers was on board of the aircraft during the accident flight. This was an "anticipatory measure" in the event of technical problems with the new aircraft."

A third opinion who may have added confusion or given wrong instructions or flipped a breaker.

This is just the thing. It was poor aeronautical decision making to attempt to figure out what is going, and there was no need to figure out what what going on. None. Zip. Nada. What needed to happen was for the pilots to quickly execute three memory items, then assess the situation further after the airplane is under full control.

I mean, look at the situation you're describing. They had a tech on board to help debug a system they knew was misbehaving that directly affected safety of flight, with revenue passengers in the back. What kind of ADM is that? And that decision was made on the ground. And given that they were anticipating stab problems, you'd think the crew would be spring-loaded to execute the runaway trim procedures at the first sign of trouble. But it is obvious they never did this. Maybe we'll find out from the CVR why. If it is because they thought they could figure it out, it will be a textbook case of poor ADM.

I'm of the view Boeing has blood on their hands for the engineering.
One of the many questions put forth to the FAA by The Aviation Herald (http://avherald.com/h?article=4bf90724/0008&opt=0):

- Why was the MCAS permitted to operate on the base of a single AoA value showing too high angle of attacks? Why does the MCAS not consider the other AoA value?

I tend to agree that Boeing probably screwed up. That doesn't mean the pilots didn't screw up. This is not unlike AF447 where a bad pitot heater design allowed the pitot system to fail, which caused the computer to stop providing envelope protection -- but that did not force the pilot to execute a zoom climb and then stall the aircraft.

The forum poster, about knowing to shut off a system you don't even know about:
"As a captain on Boeing 737, I feel betrayed about Boeing's statements about their documentation. Even as of now, the MCAS has not been incorporated into the FCOM, nor into the FCTM. Their press release is a shameless lie."

The pilot is being misleading, as you do not have to shut off a system you don't know about. You have to shut off the stab trim system.

I think Boeing's position on this is pretty clear: if you follow the procedure, it doesn't matter. Some pilots are saying it does matter. We'll find out.
Title: Cockpit voice recorder recovered
Post by: BravoV on January 14, 2019, 04:53:21 am
Update today , the CVR is recovered, buried 8 meters underneath the mud in about 30 meters deep.

https://www.reuters.com/article/us-indonesia-crash-recorder/indonesian-officials-say-crashed-lion-air-jets-cockpit-voice-recorder-found-idUSKCN1P808C?il=0 (https://www.reuters.com/article/us-indonesia-crash-recorder/indonesian-officials-say-crashed-lion-air-jets-cockpit-voice-recorder-found-idUSKCN1P808C?il=0)

Local news mentioned they used ROV with side scan sonar, magnetometer to find it.

(https://akcdn.detik.net.id/community/media/visual/2019/01/14/ce31cbf1-2fb1-4fec-b5d5-804d5994d659.jpeg?w=650&q=90)
Title: Re: Cockpit voice recorder recovered
Post by: raptor1956 on January 14, 2019, 05:59:41 am
Update today , the CVR is recovered, buried 8 meters underneath the mud in about 30 meters deep.

https://www.reuters.com/article/us-indonesia-crash-recorder/indonesian-officials-say-crashed-lion-air-jets-cockpit-voice-recorder-found-idUSKCN1P808C?il=0 (https://www.reuters.com/article/us-indonesia-crash-recorder/indonesian-officials-say-crashed-lion-air-jets-cockpit-voice-recorder-found-idUSKCN1P808C?il=0)

Local news mentioned they used ROV with side scan sonar, magnetometer to find it.


That is good news and hopefully this will clear up the actions the pilots made and provide an insight into the sequence of actions they took.  The great question is:  why did they not turn of the Stab Trim and did they talk about doing so.

The upside to the crash, if there is an upside, is that there can't be a single 737MAX pilot that does not now know what MCAS is and how and when to power off the Stab Trim.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on January 14, 2019, 06:21:30 am
Hopefully the recording data is still ok, as from the look, the outer physical unit looks badly wrecked.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on January 14, 2019, 06:24:58 am
Hopefully the recording data is still ok, as from the look, the outer physical unit looks badly wrecked.

WOW, had not looked at the pic before, but damn that thing is busted up.  The odd thing is you would expect the damage to be less with an impact with water versus land, but at the speed it must have hit the water it might as well have been land. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on January 14, 2019, 06:47:31 am
Well crash landings on water are not actually any better than on land.

At the sort of speeds an impact with water makes it feel pretty much as hard as rock. But with the extra problem of also being very slippery and easy to dig into at the same time, if something actually does poke down into the water it experiences a massive amount of drag that slows it down very fast. So when something like the end of a wing touches the water surface the whole plane will suddenly be jerked into a sharp turn before the wing can't take it anymore and tears apart. Once the plane stops its not air tight anymore so it will just sink like a rock and if you do make it out alive you are now swimming in the middle of the sea with no land in sight while the top layer of water if full of kerosine.

Then again such a noise first crash straight into land would be impossible to survive too. But a more controlled crash landing is certainly more survivable on a open field of land rather than at sea.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on January 14, 2019, 07:00:22 am
Hopefully the recording data is still ok, as from the look, the outer physical unit looks badly wrecked.

WOW, had not looked at the pic before, but damn that thing is busted up.  The odd thing is you would expect the damage to be less with an impact with water versus land, but at the speed it must have hit the water it might as well have been land. 


Brian

See for youself for.more.photos ...

https://m.detik.com/news/foto-news/d-4383483/penampakan-cvr-lion-air-pk-lqp-yang-akhirnya-ditemukan
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SeanB on January 14, 2019, 07:24:36 am
Data capsule is intact, so should read out perfectly well once taken apart. Broke off the electronics section as designed. Just have to hope the data is not degraded from all the overwrites it has had.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Don Hills on January 14, 2019, 08:57:02 am
...  Just have to hope the data is not degraded from all the overwrites it has had.

Do the math... it was a new plane, so not many running hours (flight hours plus ground running). I believe they record at least the last 30 minutes, so 2 writes per hour...  Not a problem, even for ordinary consumer flash.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on January 22, 2019, 08:25:35 pm
124 minutes of voice recordings from the CVR transcribed, including the final 15 minutes.

"Lion Air crash investigators will not release the contents of the flight's black box voice recordings until August or September." 
Another 9 months before it gets released  :-//
NTSB has their investigation on hold due to the US Gov't shutdown.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on January 22, 2019, 08:43:39 pm
Hopefully the recording data is still ok, as from the look, the outer physical unit looks badly wrecked.

WOW, had not looked at the pic before, but damn that thing is busted up.  The odd thing is you would expect the damage to be less with an impact with water versus land, but at the speed it must have hit the water it might as well have been land. 


Brian

See for youself for.more.photos ...

https://m.detik.com/news/foto-news/d-4383483/penampakan-cvr-lion-air-pk-lqp-yang-akhirnya-ditemukan

Water is practically as hard as concrete when impacted at high speed. An airliner that hits water or ground going ~500mph pretty much shatters into tiny particles. It's something a lot of conspiracy theorists fail to understand, expecting to see recognizable airplane wreckage.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 10, 2019, 11:53:50 am
Another 737 MAX:

https://www.youtube.com/watch?v=I3FDm3s2_VY (https://www.youtube.com/watch?v=I3FDm3s2_VY)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on March 10, 2019, 02:22:35 pm
The pilot is being misleading, as you do not have to shut off a system you don't know about. You have to shut off the stab trim system.

I think Boeing's position on this is pretty clear: if you follow the procedure, it doesn't matter. Some pilots are saying it does matter. We'll find out.

If you can internalize why a system works in the way it does it's generally much easier to work with it than just having a bunch of arcane rules. Now at some point the mental model can become too complex too, but that's clearly not the case here.

Just that if Boeing actually changes the manual at this point it's admitting partial guilt, so they feel they can't. So they need to be forced to and penalized for avoiding taking some responsibility.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 10, 2019, 04:57:30 pm
Another 737:
Well, the 737 product line as a whole has possibly the best overall safety record, statistically speaking, of any airliner. (There are 1200 737's in the air at any given moment!!!)

But for two 737 MAX's to crash like this in just a few months, that is very odd indeed.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 10, 2019, 06:10:35 pm
Boeing's MCAS software update, as an emergency measure by the FAA and Boeing, deployment delayed for months. It was due January but now maybe after April 2019.
"...Boeing is examining whether the anti-stall system should also check data from the second probe before engaging"
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 11, 2019, 06:22:37 am
Too soon to say what happened for sure, but the similarities with the Lionair crash has to point a finger at MCAS as a logical place to look at.  The FDR will be revealing but as with the Lionair crash I think the CVR may well be more revealing if crew response to a problem played a role.  If it turns out that this is another case of MCAS taking over and the pilots not knowing what to do then Ethiopian Air has some explaining to do on the pilot training program.  If the pilots fought the MCAS system for 5 minutes and didn't turn off the Stab Trim then whatever blame Boeing gets, and probably deserves, should be shared equally with the pilots and the airline.  Can there be a 737 Max pilot that does not know about MCAS and how to respond when it acts up anywhere in the world at this point?


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: sleemanj on March 11, 2019, 06:36:22 am
At this point, if it's a Boeing (737 MAX) I ain't going.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 11, 2019, 06:49:07 am
When i saw the news i quickly remembered this very thread. The similarities between the crashes are quite striking.

Id imagine things are getting quite tense among the upper management at Boeing now.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 11, 2019, 07:07:39 am
Flightradar24 data regarding the crash of Ethiopian Airlines flight 302:
https://www.flightradar24.com/blog/flightradar24-data-regarding-the-crash-of-ethiopian-airlines-flight-302/ (https://www.flightradar24.com/blog/flightradar24-data-regarding-the-crash-of-ethiopian-airlines-flight-302/)

What-is-the-boeing-737-max-MCAS?
https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/ (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: FlyingHacker on March 11, 2019, 07:33:51 am
As a pilot I can say an Angle of Attack (AOA) indicator is a suitable safety measure for when the pitot tube is clogged and you have no airspeed indication. The main thing a pilot is using the airspeed indicator for is to set the Angle of Attack to a safe measure to avoid a stall (lots of other stuff, too, but that is the one that usually kills you).

The 737 MAX has had bulletins on its AOA indicator. So perhaps it was multiple sensor failure.

A pilot is trained to cross check data from multiple sensors during IFR flight. We learn how to identify various failures. I can tell you from various in-flight failures (instrumentation as well as single engine loss of power) that this does take a moment to identify the issue, but the first thing I do is pitch forward (nose down) to decrease my AOA when diagnosing issues. If this means you can't hold your altitude immediately declare and emergency and work from there. Rule one of being a pilot is FLY THE AIRPLANE.

I feel like a lot of commercial pilots are so concerned about ATC deviations and possible career ramifications that they hesitate to declare emergencies or take emergency action prior to declaring.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: soldar on March 11, 2019, 08:56:02 am
Flightradar24 data regarding the crash of Ethiopian Airlines flight 302:
https://www.flightradar24.com/blog/flightradar24-data-regarding-the-crash-of-ethiopian-airlines-flight-302/ (https://www.flightradar24.com/blog/flightradar24-data-regarding-the-crash-of-ethiopian-airlines-flight-302/)
I do not understand the graphs and they seem contradictory to me.

Compare altitude with rate of climb. When the aircraft is climbing it should be gaining altitude and yet at first it gains altitude while not climbing and later it climbs without gaining altitude.  Maybe the two lines are shifted with respect to each other? Or am I misunderstanding anything?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 11, 2019, 10:07:18 am
I do not understand the graphs and they seem contradictory to me.

Yes, and I don't know what's going on:

(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=673662;image)

Here's the chart of the previous 737-MAX crash https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/ (https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/) It says "derived Vertical speed", I don't know in what sense is the word derived used. Most of it makes sense but in a few spots the data is contradictory too.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 11, 2019, 10:51:28 am
The CVR has been found. Hopefully it's not too damaged.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: AndyC_772 on March 11, 2019, 11:01:10 am
Slightly OT, but is it the case that one recorder only logs voice, while the other only logs data?

Is there a compelling reason why a single recorder can't log both? Or why both recorders don't each log everything?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 11, 2019, 11:18:55 am
Some level of redundancy I guess. I'm not sure if modern CVRs still use tape rather than the Flash used in the FDR.  You'd hope that, with advancing technology, they'd move to two recorders, each recording both voice and data.

I suppose there is a huge amount of testing, not to mention backward compatibility involved in bringing new black boxes into service.


EDIT: It looks as if they are made http://www.aircpa.com/product/combined-cvr-fdr-wembedded-rips-cvfdr-145r/ (http://www.aircpa.com/product/combined-cvr-fdr-wembedded-rips-cvfdr-145r/) I found some reference to them being used on the 787 too.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 11, 2019, 11:40:42 am
I'm guessing the reason for separate black box recorders is historical

Back when these things ware analog and used magnetic tape meant it was likely easier to build one optimized for mono audio while another box was designed for lower bandwidth sensor data but with many channels, Perhaps using multitrack heads or stuffing all the channels into one track using modulation and multiplexing.

Now that its all flash it doesn't really make a difference, but yeah id imagine its not easy to change it due to all the paperwork needed to do so. All existing aircraft also have wiring harnesses prepared for this kind of dual black box setup and likely couldn't very easily be upgraded to the new standard.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 11, 2019, 11:52:56 am
Quote
Gebeyehu Fikadu, an eyewitness to Sunday's fatal crash about two-hour drive south of the Ethiopian capital of Addis Ababa, told CNN that the plane was "swerving and dipping" and belching smoke as it came down. 

"I was in the mountain nearby when I saw the plane reach the mountain before turning around with a lot of smoke coming from the back and then crashed at this site," said the 25-year-old, who was collecting firewood on the mountain with three other locals when it happened.

"It crashed with a large boom. When it crashed luggage and clothes came burning down.

"Before it crashed the plane was swerving and dipping with a lot of smoke coming from the back and also making a very loud unpleasant sound before hitting the ground."
https://edition.cnn.com/world/live-news/ethiopian-airlines-plane-crash/index.html#h_f2affeaf6e5854fe7c4236c32490db45
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 11, 2019, 04:04:50 pm
FDR now also found.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 11, 2019, 05:28:40 pm
I'm guessing the reason for separate black box recorders is historical

Back when these things ware analog and used magnetic tape meant it was likely easier to build one optimized for mono audio while another box was designed for lower bandwidth sensor data but with many channels, Perhaps using multitrack heads or stuffing all the channels into one track using modulation and multiplexing.

Now that its all flash it doesn't really make a difference, but yeah id imagine its not easy to change it due to all the paperwork needed to do so. All existing aircraft also have wiring harnesses prepared for this kind of dual black box setup and likely couldn't very easily be upgraded to the new standard.
What's kinda crazy is that, due to magnetic tape (and paper) being too sensitive to heat, pre-Flash CVRs and FDRs used metal tape (and in some really old ones, wire) as the magnetic recording medium. Older FDR models didn't even do it magnetically, but rather used styluses that engraved the data onto wide metal tape -- just like a polygraph or seismograph, except with a stylus instead of a pen.

I'm actually kinda surprised that we even still rely on CVRs and FDRs, since satellite-based, real-time, server-side logging is available. It is used by some airlines. Streaming all that means that you have it instantly, and it doesn't matter whether you find the black boxes. (I'm sure there are occasions where streaming fails, so I wouldn't say to get rid of black boxes entirely, but just to relegate them to being backups.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 11, 2019, 06:40:03 pm
Quote
Gebeyehu Fikadu, an eyewitness to Sunday's fatal crash about two-hour drive south of the Ethiopian capital of Addis Ababa, told CNN that the plane was "swerving and dipping" and belching smoke as it came down. 

"I was in the mountain nearby when I saw the plane reach the mountain before turning around with a lot of smoke coming from the back and then crashed at this site," said the 25-year-old, who was collecting firewood on the mountain with three other locals when it happened.

"It crashed with a large boom. When it crashed luggage and clothes came burning down.

"Before it crashed the plane was swerving and dipping with a lot of smoke coming from the back and also making a very loud unpleasant sound before hitting the ground."
https://edition.cnn.com/world/live-news/ethiopian-airlines-plane-crash/index.html#h_f2affeaf6e5854fe7c4236c32490db45


If there was smoke coming from the plane, and particularly if it wasn't clearly identified with and engine, could completely change the picture of what happen and surely opens the door to something nefarious going on.  If there was an onboard fire or cabin or cargo hold explosion it's quite possible we would have seen a similar flight profile and ultimate crash.  But, as with so many cases, eye witness accounts are often the least trust worthy even when a competent person is involved and the average passer by is next to useless in these maters.

It's also possible that the pilots were jacking the throttles around as a consequence of an MCAS takeover and it is possible that could produce some smoke.

If the reports are true that both the CVR and FDR have been found and they are in decent shape we should get a preliminary report pretty soon given the stand-down ordered for more than 100 737 Max AC -- if there was evidence that the problem wasn't MCAS and was a cargo fire then that should permit the grounded AC to resume flying.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: edy on March 11, 2019, 09:48:07 pm
I do not understand the graphs and they seem contradictory to me.

Yes, and I don't know what's going on:

(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=673662;image)

Here's the chart of the previous 737-MAX crash https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/ (https://www.flightradar24.com/blog/flightradar24-data-regarding-lion-air-flight-jt610/) It says "derived Vertical speed", I don't know in what sense is the word derived used. Most of it makes sense but in a few spots the data is contradictory too.


I don't know what measurements are actually being tracked by flightradar24 but if it is just GPS coordinates (or "pings") every once in a while, it would have a location in 3D space which includes coordinates and altitude. The "derived" part would be vertical speed, which would essentially be the derivative of the altitude measurement (i.e. the delta or slope of the altitude). So if you see your altitude changing by 100 feet every minute... 0, 100, 200, 300, 400... you have a gradual slope in altitude, during that time the "derived" vertical speed would be a constant 100 per minute. When it flattens to 400, 400, 400, 400... you would see vertical speed become 0 on that part of the altitude curve (i.e. flat or zero slope). The ground speed would therefore simply be the change in the X,Y (GPS) coordinates. Now since we are looking at 3D vectoring there would be more complex way to determine airspeed because you would then include the vertical in that as well with the ground speed, do XYZ vector and determine actual velocity through air. Then again, there is also wind that complicates things. I'm not sure how flightradar is tracking things but I'm sure the "blackbox" on the airplane has the detail they will need to determine what happened.

Not being a pilot, I am actually surprised at how much of the flight is "fly by wire" and relying on instruments. I guess at that level of airplane you need to... I can only imagine flying a Cessna, looking out the window, feeling the G-forces and wind and hearing the engine noise to determine whether I am properly flying the thing. Someone mentioned earlier in the thread that pilots want to stay in that flight path regardless as deviation may cause disciplinary actions, instead of just FLYING THE PLANE no matter where and how and at what speed and altitude.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 11, 2019, 10:34:53 pm
Not being a pilot, I am actually surprised at how much of the flight is "fly by wire" and relying on instruments.

Let's not go down this rabbit hole again, like we did way earlier in this thread. The 737 is NOT a fly by wire aircraft, and uses hydraulic control systems. That includes the 737 MAX, with the exception of the spoiler system. The term "fly by wire" means that the interface between the pilots controls is interpreted and converted to electronic signals transmitted to the actuators for flight surfaces via signal wires.

As for paying attention to instruments, that's part of the job, but doesn't mean they aren't looking and feeling as well. If you're suggesting that the pilots were unaware they weren't climbing properly and had failed to notice they never got more than a few hundred feet off the ground before running into rising terrain, that is clearly not the case. Even passengers would notice that difference in "feel" from a normal takeoff, without looking out the windows.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: edy on March 11, 2019, 10:59:43 pm
Not being a pilot, I am actually surprised at how much of the flight is "fly by wire" and relying on instruments.

Let's not go down this rabbit hole again, like we did way earlier in this thread. The 737 is NOT a fly by wire aircraft, and uses hydraulic control systems.

Yes thank you for the correction and clarification, as I misspoke about the "fly by wire". I am not sure how the controls and the mechanics interconnect, so I used the term incorrectly to refer to this. What I was trying to get at was whether in the evolution of flight training from smaller aircraft to larger ones, we see a gradual diminishing in flying relying on feedback directly from what you see, hear and feel, and more reliance on instrumentation and indicators? Is this due to the level of experience needed by the pilot, the conditions (night time, no visibility) that is expected in training, the larger aircraft (versus a small one which perhaps may respond more quickly to external forces and changes)? Not being a pilot I am not sure why someone mentioned earlier in the thread that when something starts going "wrong" whether going off-road (so to speak) with the plane and just flying it based on basic principles and "gut" feedback and ignoring the instruments is practical or just not possible in a large modern airplane.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 12, 2019, 06:33:57 am
Flying by feel can become very misleading actually.

You can feel fast changes in speed or orientation very well because of feeling forces on your seat and the "biological gyroscope" in your ear. But both of these don't notice any slow long term change as you sort of get used to it along the slow change. Just like real gyroscope sensors our biological ones have trouble with long term drift.

Having no visibility and not looking at the instruments you can easily fly banked to the right 30 degrees but being absolutely certain you are perfectly level. If the bank angle builds up very slowly you just get used to it and take it as a new "zero reference" had someone corrected it back to level quickly you would swear that you are banking the other way rather than straightening out. What makes things worse with planes is that banks are used to steer left and right, because of this the acceleration from the turn is always pointing down. A bubble level in a plane would stay centered in the middle on a correctly executed turn. You don't feel yourself pulled to the side at all, the only clue is that looking out the window you can see the sky looks sideways.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on March 12, 2019, 07:12:41 am
Flying straight by eye is one thing, not as hard as flying level by eye.

The tall dashboard in the Cessna's I've had a play in are high for a reason when you're flying VFR so to help you keep a cockpit horizon to keep somewhere level.
First I thought the altimeter was the thing to watch all the time but no, you only check it from time to time to keep well in your allotted airspace and use the top of the dash to some distant point to keep yourself close to level flight.

Even when doing a 180 to line up for landing, if it was dark you'd have no idea you were both descending and turning without instruments, as the bodily feedback was so minimal unless you really cranked it over.
When my daughter did her initial IFR training they wore like a low brimmed hat so to not be able to see out the windscreen and so have to rely on instruments.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 12, 2019, 04:08:22 pm
Many countries (also ours) is closing their airspace for 737-max planes.
This is I think the first time this is going on in so many countries ?  :-//
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 12, 2019, 04:25:54 pm
Boeing: UK joins wave of countries grounding the 737 Max
https://www.bbc.com/news/world-asia-47536502?intlink_from_url=https://www.bbc.com/news/topics/cv06837xl7lt/ethiopian-airlines-crash&link_location=live-reporting-story (https://www.bbc.com/news/world-asia-47536502?intlink_from_url=https://www.bbc.com/news/topics/cv06837xl7lt/ethiopian-airlines-crash&link_location=live-reporting-story)
Quote
The UK's Civil Aviation Authority (CAA) has banned the Boeing 737 MAX from operating in or over UK airspace "as a precautionary measure".
[...]
In the aftermath of the accident, Ethiopia, Singapore, China, France, Ireland, Germany, Australia, Indonesia and Malaysia have all temporarily suspended the 737 Max.
Title: Re: Cockpit voice recorder recovered
Post by: macboy on March 12, 2019, 05:45:24 pm
(emphasis below is mine)
Update today , the CVR is recovered, ...

That is good news and hopefully this will clear up the actions the pilots made and provide an insight into the sequence of actions they took.  The great question is:  why did they not turn of the Stab Trim and did they talk about doing so.

The upside to the crash, if there is an upside, is that there can't be a single 737MAX pilot that does not now know what MCAS is and how and when to power off the Stab Trim.


Brian

Sigh. Apparently not yet.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 12, 2019, 06:29:46 pm
Well the heat on Boeing is being turned up to eleven.   The EU is suspending all 737 Max flights beginning at 3PM ET. 

Flight attendant union now calls for 737 MAX fleet to be grounded.

Senator asks American, Southwest and United to voluntarily to ground their Boeing 737 MAX 8s.

Austria, Poland and Italy are the latest to ground 737 MAX 8s.

Turkish Airlines grounds all Boeing 737 MAX aircraft.

Netherlands suspends Boeing 737 MAX 8 aircraft.

Iceland and Germany join list of countries deciding to ban 737 MAX 8 aircraft.

France's aviation authority bans Boeing 737 MAX aircraft from its airspace.

Meanwhile...

Boeing says it has "full confidence" in its 737 MAX jets and isn't issuing new guidance


Brian   :popcorn:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 12, 2019, 06:36:27 pm
Boeing shares plummeting like MAX several days in a row.........(terrible as a joke but as a fact is true).

Boeing claims MCAS new software version to come.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 12, 2019, 06:44:24 pm
Boeing claims MCAS new software version to come.

An OTA update?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 12, 2019, 07:20:35 pm
Boeing claims MCAS new software version to come.
An OTA update?
Good greif noooo, after the crash.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 12, 2019, 07:21:04 pm
Boeing claims MCAS new software version to come.

An OTA update?

I really hope there's no way an OTA update could happen and expose the AC to hacking potential.  Imagine the next Bin Laden with a team of hackers devising a new "Planes Plan" with no risk to any of his people.

I have to believe the update would need to be done by Boeing employees and only Boeing employees and only on the ground.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 12, 2019, 09:15:07 pm
I would be less worried about terrorists than by all the other things that could go wrong with an OTA update. I've seen countless gadgets bricked by that sort of thing going wrong. Pretty sure they have the sense not to design such a mechanism into an aircraft though.


As a side note, I really wish the ease of updating we have today had never been developed. It's sold on the benefits of being able to easily fix bugs and add features in the future. Unfortunately what it has done is enabled a mentality of ship the minimum viable product and finish it "later". Sorry but when I buy something I expect it to work as advertised out of the box, and to keep working until I decide to replace it. I'm not going to buy something based on promises of features to be added at some later date, and I don't want updates introducing new bugs and breaking/removing/changing features I use.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 12, 2019, 09:41:10 pm
As a side note, I really wish the ease of updating we have today had never been developed. It's sold on the benefits of being able to easily fix bugs and add features in the future. Unfortunately what it has done is enabled a mentality of ship the minimum viable product and finish it "later". Sorry but when I buy something I expect it to work as advertised out of the box, and to keep working until I decide to replace it.
I agree fully. Unfortunately this is now common practice in consumer electronics because the product development cycles has been cut at least in three compared to ten years ago.
New features are a must have in time for the next product launch otherwise the marketing team has to wait for the next time window which often is half a year or even one year and by then the competition will already sold their unfinished products.

I just hope for all our sake this is not the case for the firmware in new aircrafts.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: blueskull on March 12, 2019, 10:07:19 pm
If Boeing is to assure everyone that the 737 MAX 8 is safe, they can simply get their CxO on board one with its Pitot tube clogged and AoA sensor disabled, then hire two average 737 pilots that do not have intimate knowledge on MCAS and its quirks to fly it. I'm sure news agencies worldwide will report this intrepid action and clear their name.

That's better than any spokesmen.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 12:08:24 am
If Boeing is to assure everyone that the 737 MAX 8 is safe, they can simply get their CxO on board one with its Pitot tube clogged and AoA sensor disabled, then hire two average 737 pilots that do not have intimate knowledge on MCAS and its quirks to fly it. I'm sure news agencies worldwide will report this intrepid action and clear their name.

That's better than any spokesmen.


If Boeing were a Japanese company then doing what you said would be almost likely but very few companies act as the Japanese do in situations like this.  In fact, as the Tepco Fukushima thing demonstrated, the Japanese way isn't always practiced by the Japanese.

So the rumor is that Boeing has a MCAS update coming -- when might that be.  The problem Boeing has here is that no matter what they do they are going to be sued big time for both crashes.  On the one hand, they might have preferred this second accident never happened so they could distance themselves from the Lionair crash and a year from now if they rolled out an update they might uncouple it from the Lionair incident and, perhaps, avoid the worst of the legal problems, but with this second accident they will now have to update MCAS and soon and it will be hard for them to prove it was just an incidental thing.  Not doing something will end the 737 MAx program right now. 

Boeing is going to be eaten alive by lawyers and if the Lionair case was bad this new one probably triples what they can expect to pay and it could be 10X.  Yes yes, we don't know the MCAS was involved in this new case, not for sure anyway, but even professionals in the airline industry are pretty sure MCAS played a role.  It's not out or reach for this to take down Boeing altogether leaving only one major player in the game.  I doubt that will happen, but it is certainly a possibility.  The saving grace for Boeing may be there military contracts and the fact that those military relationships may make them 'to important to fail' by the US government.  Airbus would love that to happen as would many others in the world with a hardon against the USA, but as touch and go as it might be I don't see them fold because of this.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 13, 2019, 12:13:15 am
your analogy to Fukushima stumbles.

https://gizmodo.com/boeing-promises-to-release-software-update-for-737-max-1833224836
https://boeing.mediaroom.com/news-releases-statements?item=130402
Quote

For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 12:22:38 am
your analogy to Fukushima stumbles.

https://gizmodo.com/boeing-promises-to-release-software-update-for-737-max-1833224836
https://boeing.mediaroom.com/news-releases-statements?item=130402
Quote

For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.


I think you misunderstood my reference to Fukushima -- it wasn't about an malfeasance by Boeing but that the execs at Tepco displayed an un-Japanese practice of not putting your skin on the line as blueskull alluded to. 

Boeing has, prior to this latest crash, promised an update but has been less than forthcoming about when it will be delivered.  This new incident will not permit them to delay this and it also makes it harder for them to uncouple the update with the crashes that happened. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 13, 2019, 12:32:21 am
Well thats what i have doubts about a "un japanese action". I think Japanese is as much as cowards as rest of us are when it comes to self preservation, all this CEO crying and apologizing in public a silly show based on wicked ideas about cultural behavior, send them to jail instead. :popcorn:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 13, 2019, 12:33:48 am
A bug in the MCAS that pushes the nose down too far, overriding the pilot's nose up command, is that it, then, it seems?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 13, 2019, 12:37:10 am
I really hope there's no way an OTA update could happen and expose the AC to hacking potential.  Imagine the next Bin Laden with a team of hackers devising a new "Planes Plan" with no risk to any of his people.

I have to believe the update would need to be done by Boeing employees and only Boeing employees and only on the ground. Brian

imagine CIA instead!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 13, 2019, 12:38:32 am
Well thats what i have doubts about a "un japanese action". I think Japanese is as much as cowards as rest of us are when it comes to self preservation, all this CEO crying and apologizing in public a silly show based on wicked ideas about cultural behavior, send them to jail instead. :popcorn:

In the wake of the JAL 123 crash the president of the airline resigned, an engineer and the maintenance manager killed themselves. I don't think that would happen had it been a US based airline for example.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 13, 2019, 12:48:06 am
In the wake of the JAL 123 crash the president of the airline resigned, an engineer and the maintenance manager killed themselves. I don't think that would happen had it been a US based airline for example.
Nor an European, they would try squirm them self out like the  Lufthansa CEO did when Germanwings crash hapend.
JAL 123 crash voice recording is something to listen to, how the pilots doing all they can to save the rudder fin less oscillating 747. :phew:
Then the rescue team on the ground screwed things up so some could had been saved died.

cockpit voice recording
https://www.youtube.com/watch?v=Xfh9-ogUgSQ (https://www.youtube.com/watch?v=Xfh9-ogUgSQ)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on March 13, 2019, 01:12:22 am
Boeing has, prior to this latest crash, promised an update but has been less than forthcoming about when it will be delivered.  This new incident will not permit them to delay this and it also makes it harder for them to uncouple the update with the crashes that happened

No way to avoid that.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 01:18:32 am
Boeing has, prior to this latest crash, promised an update but has been less than forthcoming about when it will be delivered.  This new incident will not permit them to delay this and it also makes it harder for them to uncouple the update with the crashes that happened

No way to avoid that.


Nope ... There's going to be a generation of lawyers able to retire earlier than expected.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BradC on March 13, 2019, 01:44:43 am
I can't see how these could be isolated incidents. I wonder if other unreported incidents have occurred that were dealt with relatively uneventfully by following the manual?

Is there a mandatory reporting procedure for dealing with anomalies in-flight?

While being completely different, from a functionality perspective this doesn't seem that far off the 737 rudder reversal issues.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 13, 2019, 02:00:46 am
Is there a mandatory reporting procedure for dealing with anomalies in-flight?
Yes, pretty much everything abnormal in aviation requires some kind of reporting, although the consequences of not doing so may vary depending on the countries involved.

The demand for "quick fix" software updates runs squarely into the legally mandated development process for mission-critical avionics software. This is combined with the slow release of diagnostic information from accident investigations. Boeing presumably gets access to raw data prior to public release, but it still takes time to digest correctly and remains subject to NTSB (and other agency) recommendations/demands that may or may not have been met by premature action.

https://en.wikipedia.org/wiki/Avionics_software#Regulatory_issues

None of that can be skipped, so it takes time. Doing it right trumps doing it fast.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 13, 2019, 03:15:49 am
I can't see how these could be isolated incidents. I wonder if other unreported incidents have occurred that were dealt with relatively uneventfully by following the manual?

Is there a mandatory reporting procedure for dealing with anomalies in-flight?

While being completely different, from a functionality perspective this doesn't seem that far off the 737 rudder reversal issues.

Well, of course, we'll know when we know. But I am starting to think that they could just be isolated incidents. First, I just can't wrap my head around the idea that, given what happened with Lionair, that any 737 driver, including this crew, would be absolutely primed to handle a runaway stab problem by putting the system in cutout as per the flight manual. It just defies reason that the crew would find itself unprepared for a LionAir type scenario. The second reason is that an eyewitness claims he saw smoke on the way down.

Anyway, all speculation at this point. They have the CVR and FDR, so they'll know soon enough.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 03:25:24 am
Is there a mandatory reporting procedure for dealing with anomalies in-flight?
Yes, pretty much everything abnormal in aviation requires some kind of reporting, although the consequences of not doing so may vary depending on the countries involved.

The demand for "quick fix" software updates runs squarely into the legally mandated development process for mission-critical avionics software. This is combined with the slow release of diagnostic information from accident investigations. Boeing presumably gets access to raw data prior to public release, but it still takes time to digest correctly and remains subject to NTSB (and other agency) recommendations/demands that may or may not have been met by premature action.

https://en.wikipedia.org/wiki/Avionics_software#Regulatory_issues

None of that can be skipped, so it takes time. Doing it right trumps doing it fast.

Yes and that's the quandary that Boeing is in right now -- they may have a handle on the problem and a solution to it but the process, which is not only understandable but necessary, may necessitate taking longer to jump through those hoops.  My guess is that Boeing was aware of the potential for a problem before they shipped the first one but they must have felt the runaway stabilizer protocol was sufficient.  I have to say the fact that the system can command a nose down trim hen so close to the ground on only the data from one side and without reference to the other side seems criminal to me -- when the system is in doubt don't take control from the pilots. 

I can see two fixes for this:  the first, the bandaid, will be software only or if hardware is includes the hardware changes will be minor; the second one may require a third system to monitor both sides and act as an arbiter if there's a difference.  If one side could see what the other side sees from the beginning I fail to see how they could have designed the software NOT to look at the other side and not command nose down at low altitude if there's a disagreement.

Another aspect of this that boggles my mind is that the system puts stall prevention above everything, even a steep nose down attitude at low altitude.  And, once again, the idea that this AC isn't fly-by-wire is a distinction without a difference.  If the computer can interfere with the pilots control actions and override them it's kind of hard to say this isn't fly-by-wire now is it. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 03:28:23 am
I can't see how these could be isolated incidents. I wonder if other unreported incidents have occurred that were dealt with relatively uneventfully by following the manual?

Is there a mandatory reporting procedure for dealing with anomalies in-flight?

While being completely different, from a functionality perspective this doesn't seem that far off the 737 rudder reversal issues.

Well, of course, we'll know when we know. But I am starting to think that they could just be isolated incidents. First, I just can't wrap my head around the idea that, given what happened with Lionair, that any 737 driver, including this crew, would be absolutely primed to handle a runaway stab problem by putting the system in cutout as per the flight manual. It just defies reason that the crew would find itself unprepared for a LionAir type scenario. The second reason is that an eyewitness claims he saw smoke on the way down.

Anyway, all speculation at this point. They have the CVR and FDR, so they'll know soon enough.


I saw that reference to a witness claiming smoke, but as I mentioned, witness testimony is the lowest form of evidence and its common for a dozen witness to the same event describe them a dozen different and incompatible ways.  People are dreadful witnesses...


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: FrankBuss on March 13, 2019, 08:09:57 am
I don't understand why the FAA doesn't ground the 737, as many other countries do. Do they wait for a 3rd crash to be sure that there is something wrong with the plane?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 13, 2019, 08:42:11 am
I don't understand why the FAA doesn't ground the 737, as many other countries do. Do they wait for a 3rd crash to be sure that there is something wrong with the plane?
Me neither, better safe than sorry, esp. when there are 100+ lives involved each incident.
It "feels" like there are some business/politic entanglements there  ;)

But on the other hand since there is no final outcome of the investigation yet they can only take preventive measures.
It could well be a pilot error in one of the cases due to the new plane, or is there already some hard evidence out there ?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Homer J Simpson on March 13, 2019, 09:03:26 am
https://www.youtube.com/watch?v=1XCU__OEftU (https://www.youtube.com/watch?v=1XCU__OEftU)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: FrankBuss on March 13, 2019, 09:23:42 am
Right, I think the video explains it. In short, and what I've read elsewhere: The jet engines were not designed for this plane, but they used it anyway, maybe to save some money. So it doesn't really fly stable without software correction, because they are mounted at the wrong position. The software depends on sensor inputs, and I've read these AOA sensors are not redundant and can fail. If this happens, the pilot has to understand that this is the problem, and then do 3 non-obvious steps to counteract that the nose dips and that it falls out of the sky.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 13, 2019, 10:45:14 am
There has to be a bug in the MCAS software because in the previous crash both air speed (pitot) and AoA sensors had malfunctioned in the flight previous to the crash and were replaced. Four new sensors can't fail all at once twice in a 5 months period. Either the MCAS software has a bug and misreads the sensors data, like a bad pointer or something, or if it really was a sensor malfunction, the MCAS should disengage and put an alarm to the pilot when the data it's getting from the sensors does not make sense, instead of say nothing and keep pushing the nose down.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 13, 2019, 12:55:30 pm
I just hope all the USA pilots are by now well trained to disable in a sec that bloody MCAS POS.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: TheSteve on March 13, 2019, 04:26:26 pm
Canada has now banned the 737 Max as well.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 13, 2019, 05:12:53 pm
As of today the following countries has grounded the 737 MAX.

Argentina,Australia,Austria,Belgium,Brazil,Bulgaria,Cayman Islands,China,Canada,Croatia,Cyprus,Czech Republic
Denmark,Estonia,Ethiopia,Finland,France,Germany,Greece,Hungary,Iceland,India,Indonesia,Ireland,Italy,Latvia
Liechtenstein,Lithuania,Luxembourg,Malaysia,Malta,Mexico,Mongolia,Morocco,Netherlands,Norway,Oman,Poland
Portugal,Romania,Singapore,Slovakia,Slovenia,South Africa,South Korea,Spain,Sweden,Switzerland,Turkey,United Kingdom
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 13, 2019, 06:15:10 pm
US almost stands alone. Looks like the CEO of Boeing called his "friend" Trump.
Now if something does go wrong, that will have huge consequences.

https://edition.cnn.com/2019/03/13/politics/donald-trump-boeing-faa/index.html
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 06:35:43 pm
Trump is reported to have lobbied Vietnam on the 737 Max so I'm not sure what arrangement he has with Boeing though if Trump is anything it is money hungry. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 13, 2019, 06:45:21 pm
As of today the following countries has grounded the 737 MAX.

Argentina,Australia,Austria,Belgium,Brazil,Bulgaria,Cayman Islands,China,Canada,Croatia,Cyprus,Czech Republic
Denmark,Estonia,Ethiopia,Finland,France,Germany,Greece,Hungary,Iceland,India,Indonesia,Ireland,Italy,Latvia
Liechtenstein,Lithuania,Luxembourg,Malaysia,Malta,Mexico,Mongolia,Morocco,Netherlands,Norway,Oman,Poland
Portugal,Romania,Singapore,Slovakia,Slovenia,South Africa,South Korea,Spain,Sweden,Switzerland,Turkey,United Kingdom
Most of those did not separately and independently make that decision, they're simply part of the EU authority which made the decision for all of them. It's like listing all 50+ state/territory governments of the USA whenever the Federal government makes a global decision. Making the list TLDR isn't terribly helpful, unless your intent is to obscure the non-EU countries.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 13, 2019, 06:51:16 pm
USA now also grounds the max.
Wise decision IMO.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 13, 2019, 06:52:54 pm
https://www.reuters.com/article/us-ethiopia-airplane/u-s-grounds-737-max-jets-boeing-shares-fall-again-idUSKBN1QU15W (https://www.reuters.com/article/us-ethiopia-airplane/u-s-grounds-737-max-jets-boeing-shares-fall-again-idUSKBN1QU15W)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 13, 2019, 06:56:57 pm
Well done!

Quote
Trump praised the airline manufacturer as a “great company” and said he hoped that Boeing will come up “very quickly” with answers to what caused the crash in Ethiopia, but “until they do the planes are grounded.”

https://www.youtube.com/watch?v=5_2Uqke5nf4 (https://www.youtube.com/watch?v=5_2Uqke5nf4)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Bud on March 13, 2019, 07:13:01 pm
Canada has now banned the 737 Max as well.

Have they? Just this morning driving to work CBC radio said the transportation minister said he won't.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on March 13, 2019, 07:47:00 pm
Canada has now banned the 737 Max as well.

Have they? Just this morning driving to work CBC radio said the transportation minister said he won't.

Yes, Canada banned this morning, shortly followed by the United States


For Air Canada it's a giant PITA as the B38M represents about 25% of their narrowbody fleet; and I wouldn't want to be flying domestically as I suspect there will be a lot of cancellations and re-routing

Narrowbody fleet

70  Boeing A319/320/321
24  Boeing 737-MAX8
18  Embraer 190

What it likely means is that long-haul thin flights (like Halifax/StJohns -> London, Vancouver/Calgary -> Hawaii) really don't have much of a replacement short of them putting widebodies on the routes. From what I heard, Air Canada was one of the last 737-MAX8s to leave the UK prior to the grounding.



WestJet it's a smaller percentage
109  Boeing 737-600/700/800
13  Boeing 737-MAX8


Neither AC's nor WS's  discount arms operate the B38M
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 13, 2019, 08:33:41 pm
As of today the following countries has grounded the 737 MAX.

Argentina,Australia,Austria,Belgium,Brazil,Bulgaria,Cayman Islands,China,Canada,Croatia,Cyprus,Czech Republic
Denmark,Estonia,Ethiopia,Finland,France,Germany,Greece,Hungary,Iceland,India,Indonesia,Ireland,Italy,Latvia
Liechtenstein,Lithuania,Luxembourg,Malaysia,Malta,Mexico,Mongolia,Morocco,Netherlands,Norway,Oman,Poland
Portugal,Romania,Singapore,Slovakia,Slovenia,South Africa,South Korea,Spain,Sweden,Switzerland,Turkey,United Kingdom, USA.
Most of those did not separately and independently make that decision, they're simply part of the EU authority which made the decision for all of them. It's like listing all 50+ state/territory governments of the USA whenever the Federal government makes a global decision. Making the list TLDR isn't terribly helpful, unless your intent is to obscure the non-EU countries.
I have no intent of obscure anything for anyone. STOP construct accusations!

https://nairobinews.nation.co.ke/editors-picks/us-government-warned-citizens-avoid-ethiopian-airport (https://nairobinews.nation.co.ke/editors-picks/us-government-warned-citizens-avoid-ethiopian-airport)
https://www.youtube.com/watch?v=fmOpMTZI1L0 (https://www.youtube.com/watch?v=fmOpMTZI1L0)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 13, 2019, 08:35:05 pm
Boeing themselves have now grounded the 737 Max, making individual country decisions irrelevant.

https://www.bbc.co.uk/news/business-47562727 (https://www.bbc.co.uk/news/business-47562727)

Quote
Boeing has grounded its entire global fleet of 737 Max aircraft after investigators uncovered new evidence at the scene of the fatal Ethiopian Airlines crash.

The US plane-maker said it would suspend all 371 of the aircraft.

The Federal Aviation Administration said fresh evidence as well as newly refined satellite data prompted the decision to temporarily ban the jets.

The FAA had previously held out while many countries banned the aircraft.

The crash on Sunday in Addis Ababa killed 157 people.

It was the second fatal Max 8 disaster in five months after one crashed over Indonesia in October, claiming 189 lives.

Boeing said it "continues to have full confidence in the safety of the 737 Max".

However, it said that after consultation with the FAA and the National Transportation Safety Board - which is conducting an investigation into the Ethiopian Airlines crash - it had decided to ground the flights "out of an abundance of caution and in order to reassure the flying public of the aircraft's safety".

The FAA said: "The grounding will remain in effect pending further investigation, including examination of information from the aircraft's flight data recorders and cockpit voice recorders."
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 08:41:55 pm
USA now also grounds the max.
Wise decision IMO.


I wonder if the decision to ground by the FAA is in response to data from the CVR and FDR.  I have to believe that both recorders have been downloaded and a preliminary (very preliminary) review has been done and that the data is indicating a similarity with Lionair that relates to MCAS.

One thing that is new here is that numerous reports of 737 Max pilots to weirdness when autopilot is turned on but in the past we were told MCAS only activates when AP is off so perhaps there's other flight control software problems beyond MCAS or MCAS plays a role while autopilot is engaged as well.  Honestly, we can put to bed the idea that this isn't a fly-by-wire AC even if it's not fly-by-wire by the conventional definition -- if the computer can wrestle control in AP or when AP is off AND the only way to prevent that is to turn systems off the idea that this is a stick flown AC is laughable. 

So, in the past we were told MCAS only activated when being stick flown but the new data says the same or similar problems can also occur on AP.

Boeing is going to eat this one big time!


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 08:44:47 pm
Boeing themselves have now grounded the 737 Max, making individual country decisions irrelevant.

https://www.bbc.co.uk/news/business-47562727 (https://www.bbc.co.uk/news/business-47562727)

Quote
Boeing has grounded its entire global fleet of 737 Max aircraft after investigators uncovered new evidence at the scene of the fatal Ethiopian Airlines crash.

The US plane-maker said it would suspend all 371 of the aircraft.

The Federal Aviation Administration said fresh evidence as well as newly refined satellite data prompted the decision to temporarily ban the jets.

The FAA had previously held out while many countries banned the aircraft.

The crash on Sunday in Addis Ababa killed 157 people.

It was the second fatal Max 8 disaster in five months after one crashed over Indonesia in October, claiming 189 lives.

Boeing said it "continues to have full confidence in the safety of the 737 Max".

However, it said that after consultation with the FAA and the National Transportation Safety Board - which is conducting an investigation into the Ethiopian Airlines crash - it had decided to ground the flights "out of an abundance of caution and in order to reassure the flying public of the aircraft's safety".

The FAA said: "The grounding will remain in effect pending further investigation, including examination of information from the aircraft's flight data recorders and cockpit voice recorders."


Ahh, so it looks like the investigation has already revealed information that points to a problem with the AC.  I would not want to be in the Boeing PR department right now...


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 13, 2019, 08:45:53 pm
Boeing themselves have now grounded the 737 Max, making individual country decisions irrelevant.
They should have done that much earlier IMO, now it is more a joke since 3/4 of the world already took that decision for them.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MasterTech on March 13, 2019, 08:54:21 pm
USA now also grounds the max.
Wise decision IMO.


I wonder if the decision to ground by the FAA is in response to data from the CVR and FDR.  I have to believe that both recorders have been downloaded and a preliminary (very preliminary) review has been done and that the data is indicating a similarity with Lionair that relates to MCAS.


It’s due to ADSB flight path data collected from satellites, that probably has more points that what is available to the public right now from flightaware. This is what made Canada ground them, and now the FAA, probably the pattern is the same as the indonesian plane.

As to the black boxes, ethiopian authorities wants them investigated in EU territory as they dont trust the US, however germany declined saying they dont have the software to decode them
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 13, 2019, 09:05:09 pm
New black boxes, who can read them?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on March 13, 2019, 09:13:46 pm
One thing that is new here is that numerous reports of 737 Max pilots to weirdness when autopilot is turned on but in the past we were told MCAS only activates when AP is off so perhaps there's other flight control software problems beyond MCAS or MCAS plays a role while autopilot is engaged as well.  Honestly, we can put to bed the idea that this isn't a fly-by-wire AC even if it's not fly-by-wire by the conventional definition -- if the computer can wrestle control in AP or when AP is off AND the only way to prevent that is to turn systems off the idea that this is a stick flown AC is laughable. 

So, in the past we were told MCAS only activated when being stick flown but the new data says the same or similar problems can also occur on AP.

The 737 (everything from the -100 to MAX10) is not a fly by wire aircraft.  The difference is how the control surfaces are connected to the control inputs.  In the case of all 737s it's done mechanically/hydraulically, and the stick directly controls the hydraulics.  That's not to say there's aren't systems like the AP or MCAS (stick shaker) that can't control the stick.

On the A320s, the input is purely a joystick into an electronic brain, aka fly-by-wire; which then actuates electro-hydraulic systems.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on March 13, 2019, 09:20:11 pm
Equally interesting is the Atlas Air 767 crash two weeks ago; where they've now released some of the FDR info


...Also, about this time, the FDR data indicated that some small vertical accelerations consistent with the airplane entering turbulence. Shortly after, when the airplane’s indicated airspeed was steady about 230 knots, the engines increased to maximum thrust, and the airplane pitch increased to about 4° nose up. The airplane then pitched nose down over the next 18 seconds to about 49° in response to nose-down elevator deflection. (Editorial Note: the sentence originally read: "and then rapidly pitched nose down to about 49° in response to column input." and was later edited by the NTSB). The stall warning (stick shaker) did not activate.
...

AVHerald.com as always has much more information.
Atlas Air 3591: http://avherald.com/h?article=4c497c3c&opt=0 (http://avherald.com/h?article=4c497c3c&opt=0)
Ethiopian 302: http://avherald.com/h?article=4c534c4a&opt=0 (http://avherald.com/h?article=4c534c4a&opt=0)
Lion Air 610: http://avherald.com/h?article=4bf90724/0009&opt=0 (http://avherald.com/h?article=4bf90724/0009&opt=0)


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Bud on March 13, 2019, 09:54:36 pm
Canada has now banned the 737 Max as well.

Have they? Just this morning driving to work CBC radio said the transportation minister said he won't.

Yes, Canada banned this morning, shortly followed by the United States
Followed by. Yes tell me about it. CBC was reporting all night long yesterday and this morning that the minister "does not have plans to ground the planes", quote/unquote. This guy is full of shit . Let me offer an explanation: this piece of shit minister heard that the US will do it.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 13, 2019, 10:05:54 pm
Equally interesting is the Atlas Air 767 crash two weeks ago; where they've now released some of the FDR info

There's a video of that crash:

https://www.youtube.com/watch?v=-_YURUIvSpI (https://www.youtube.com/watch?v=-_YURUIvSpI)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 10:19:48 pm
One thing that is new here is that numerous reports of 737 Max pilots to weirdness when autopilot is turned on but in the past we were told MCAS only activates when AP is off so perhaps there's other flight control software problems beyond MCAS or MCAS plays a role while autopilot is engaged as well.  Honestly, we can put to bed the idea that this isn't a fly-by-wire AC even if it's not fly-by-wire by the conventional definition -- if the computer can wrestle control in AP or when AP is off AND the only way to prevent that is to turn systems off the idea that this is a stick flown AC is laughable. 

So, in the past we were told MCAS only activated when being stick flown but the new data says the same or similar problems can also occur on AP.

The 737 (everything from the -100 to MAX10) is not a fly by wire aircraft.  The difference is how the control surfaces are connected to the control inputs.  In the case of all 737s it's done mechanically/hydraulically, and the stick directly controls the hydraulics.  That's not to say there's aren't systems like the AP or MCAS (stick shaker) that can't control the stick.

On the A320s, the input is purely a joystick into an electronic brain, aka fly-by-wire; which then actuates electro-hydraulic systems.

And once again this is a distinction without a difference.  I've worked on AC (USAF) and know a thing or two about them and, yes, there is a definition related to fly-by-wire and the 737 does not meet that definition -- however, if the computer can still override the pilots inputs to the stick this distinction is largely irrelevant.  The pertinent point is that a computer is controlling things and it makes little difference if the pilot has a direct connection to the control surfaces or if the computer is in between -- if the computer can wrestle control from the pilot the end effect is the same.  In fact, the idea that a pilot has direct control of the control surfaces on a 737 is laughable anyway as there's a hydraulic system in between -- not like AC where the yoke directly connects to the control surfaces with cables.  Look, we've been down this semantic road before and its tiring to continue the pretense that an AC like the 737 isn't controlled by computer even if a formal definition would argue it isn't.  It is a sure bet that most if not all the update Boeing plans is SOFTWARE.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 10:24:19 pm
Equally interesting is the Atlas Air 767 crash two weeks ago; where they've now released some of the FDR info

There's a video of that crash:

https://www.youtube.com/watch?v=-_YURUIvSpI (https://www.youtube.com/watch?v=-_YURUIvSpI)


The thing that strikes me about this video is that there is little roll activity -- the plane just flies straight into the swamp.  I also note the absence of any smoke suggesting the problem is unlikely to be engine or cargo fire related. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 13, 2019, 10:28:48 pm
The thing that strikes me about this video is that there is little roll activity -- the plane just lies straight into the swamp.  I also note the absence of any smoke suggesting the problem is unlikely to be engine or cargo fire related.

Here's some info:

https://www.youtube.com/watch?v=nJo2jGz34uM (https://www.youtube.com/watch?v=nJo2jGz34uM)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: pilotchup on March 13, 2019, 10:33:10 pm
Man this thread has blown up into a long one, so I haven't read everything here yet.
I'm interested in this, as is the rest of the aviation and some of the engineering community I bet.
I am a instrument rated pilot.
One thing I can say, is that airline pilots rarely fly in the traditional sense anymore, because of all the automation and systems. Not good nor bad, it's just how the industry is now. The extent that airline pilots "fly" is more like babysitting a system, with some manual control often done during take-off and landings depending on the capabilities of the airport in use and systems onboard. When something goes wrong, the pilots look at each other and say "whys it doing that" instead of disengaging the autopilot (breaking the circuit breaker if it is a safety system that is not disconnected with autopilot), grabbing the controls, and fly the darn plane. I may be ignorant here not reading all the circumstances and evidence yet, but just my initial 2 cents.. carry on!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 13, 2019, 10:44:30 pm
One thing that is new here is that numerous reports of 737 Max pilots to weirdness when autopilot is turned on but in the past we were told MCAS only activates when AP is off so perhaps there's other flight control software problems beyond MCAS or MCAS plays a role while autopilot is engaged as well.  Honestly, we can put to bed the idea that this isn't a fly-by-wire AC even if it's not fly-by-wire by the conventional definition -- if the computer can wrestle control in AP or when AP is off AND the only way to prevent that is to turn systems off the idea that this is a stick flown AC is laughable. 

So, in the past we were told MCAS only activated when being stick flown but the new data says the same or similar problems can also occur on AP.

The 737 (everything from the -100 to MAX10) is not a fly by wire aircraft.  The difference is how the control surfaces are connected to the control inputs.  In the case of all 737s it's done mechanically/hydraulically, and the stick directly controls the hydraulics.  That's not to say there's aren't systems like the AP or MCAS (stick shaker) that can't control the stick.

On the A320s, the input is purely a joystick into an electronic brain, aka fly-by-wire; which then actuates electro-hydraulic systems.

And once again this is a distinction without a difference.  I've worked on AC (USAF) and know a thing or two about them and, yes, there is a definition related to fly-by-wire and the 737 does not meet that definition -- however, if the computer can still override the pilots inputs to the stick this distinction is largely irrelevant.  The pertinent point is that a computer is controlling things and it makes little difference if the pilot has a direct connection to the control surfaces or if the computer is in between -- if the computer can wrestle control from the pilot the end effect is the same.  In fact, the idea that a pilot has direct control of the control surfaces on a 737 is laughable anyway as there's a hydraulic system in between -- not like AC where the yoke directly connects to the control surfaces with cables.  Look, we've been down this semantic road before and its tiring to continue the pretense that an AC like the 737 isn't controlled by computer even if a formal definition would argue it isn't.  It is a sure bet that most if not all the update Boeing plans is SOFTWARE.


Brian

Saying something is fly-by-wire when it's fly-by-hydraulic is like saying an electric water heater is the same as an gas one, just because they both accomplish the same goal. I agree that the problem likely is not in the method of transmitting force to the actuators, but that's no excuse for using a term describing that method to describe something else. If it's a software problem, call it a software or computer problem. If its a sensor problem, call it a sensor problem. Using the wrong term will get you push-back, as you've discovered multiple times in this thread already.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: blueskull on March 13, 2019, 10:52:05 pm
And the loyal congressman of GOP stated the other countries banned the aircraft prematurely not "based in" fact.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on March 13, 2019, 11:25:37 pm
Not mentioned here, but there have been a few other similar airdata computer/autopilot plunge accidents (bad data=bad programmed response); such as

A330-200  Air France 447 crashed off the coast of Brazil
A330-300 Qantas 72 which diverted to Learmonth

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 13, 2019, 11:27:23 pm
One thing that is new here is that numerous reports of 737 Max pilots to weirdness when autopilot is turned on but in the past we were told MCAS only activates when AP is off so perhaps there's other flight control software problems beyond MCAS or MCAS plays a role while autopilot is engaged as well.  Honestly, we can put to bed the idea that this isn't a fly-by-wire AC even if it's not fly-by-wire by the conventional definition -- if the computer can wrestle control in AP or when AP is off AND the only way to prevent that is to turn systems off the idea that this is a stick flown AC is laughable. 

So, in the past we were told MCAS only activated when being stick flown but the new data says the same or similar problems can also occur on AP.

The 737 (everything from the -100 to MAX10) is not a fly by wire aircraft.  The difference is how the control surfaces are connected to the control inputs.  In the case of all 737s it's done mechanically/hydraulically, and the stick directly controls the hydraulics.  That's not to say there's aren't systems like the AP or MCAS (stick shaker) that can't control the stick.

On the A320s, the input is purely a joystick into an electronic brain, aka fly-by-wire; which then actuates electro-hydraulic systems.

And once again this is a distinction without a difference.  I've worked on AC (USAF) and know a thing or two about them and, yes, there is a definition related to fly-by-wire and the 737 does not meet that definition -- however, if the computer can still override the pilots inputs to the stick this distinction is largely irrelevant.  The pertinent point is that a computer is controlling things and it makes little difference if the pilot has a direct connection to the control surfaces or if the computer is in between -- if the computer can wrestle control from the pilot the end effect is the same.  In fact, the idea that a pilot has direct control of the control surfaces on a 737 is laughable anyway as there's a hydraulic system in between -- not like AC where the yoke directly connects to the control surfaces with cables.  Look, we've been down this semantic road before and its tiring to continue the pretense that an AC like the 737 isn't controlled by computer even if a formal definition would argue it isn't.  It is a sure bet that most if not all the update Boeing plans is SOFTWARE.


Brian

Saying something is fly-by-wire when it's fly-by-hydraulic is like saying an electric water heater is the same as an gas one, just because they both accomplish the same goal. I agree that the problem likely is not in the method of transmitting force to the actuators, but that's no excuse for using a term describing that method to describe something else. If it's a software problem, call it a software or computer problem. If its a sensor problem, call it a sensor problem. Using the wrong term will get you push-back, as you've discovered multiple times in this thread already.


In every post I've made on this topic I've made it clear that the technical description of fly-by-wire does not match what the 737 Max is, the point I'm making is that this technical difference is irrelevant given the fact that the computer is controlling the control surfaces.  One could argue that fly-by-wire is inaccurate anyway if in fact the wire is an optical fiber!


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: edy on March 14, 2019, 01:32:48 am
So if Boeing grounded all the planes based on some new data found from the flight recorders, are we to assume there is some software glitch they discovered with their flight control system? Something in the software that is making an improper calculation/correction and perhaps even exaggerating the problem under certain conditions (like a run-away effect)? I'm sure there are millions of lines of code in there and somewhere earlier in the thread I believe someone mentioned that they "simulated" the behaviour of earlier planes in the new MAX series so that pilots would feel like they were flying an older plane they were used to.

I'm sure some of the experienced pilots in this thread can shed some light on what exactly modern sophisticated passenger jet software does and how it is supposed to aid pilots. Other than instrumentation, how much is the software flying the plane and how much is it just informing the pilot? This may boil down to a philosophical question regarding autonomous computer-controlled transportation in general and the statistical argument about safety versus human comfort level. For example, if you say had fully computer-controlled aircraft (from take off to landing) and found that the safety improved by a factor of 2x, would people still be willing to let a computer fly them, or would they rather have a human behind the wheel even knowing statistically-speaking that it would double their chance of a fatal crash? Sure, the numbers tell us something but psychologically how ready are we to allow computers to take full control?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 14, 2019, 02:01:52 am
Though auto-takeoff and autoland (in addition to the cruise autopilot) have actually existed for many decades, making it theoretically possible for an aircraft to have every phase of flight automated, this isn’t really done in practice.

Autopilot isn’t a single thing. It’s an umbrella term for dozens of discrete automation functions that can be used all at once, or none at all, or in any combination. So things like auto-navigation (automatic turns), auto level (maintain flight level), autothrottle (maintain speed), auto brake (on landing) etc. But tons more are automatic safeguards, like stall prevention.

In this case, they added another computer-controlled automatic adjustment to compensate for the different lift characteristics of the MAX, to make it behave like a classic 737, so that a pilot doesn’t have to be completely recertified for a different aircraft type, which would be needed if it handled differently. The problem is simply that they didn’t even mention this new system to pilots, never mind explain how to disable it when faulty sensors are causing it to make erroneous corrections, as happened with Lion Air and may have happened with Ethiopian.

Back to your question: no flight is ever under total computer control. Far from it. The pilots are coordinating the bazillions of different settings and modes, some manually, others through automation. The programming is critical (like, you must correctly enter the flight plan, so that auto nav knows when to turn). And a flight is never flown according only to pre-decided steps: air traffic control is directing them what to do, when to do it, etc. So for example, you may choose to use auto level at cruise, but you’re still in contact with air traffic control, who tell you which flight level to use, and you must enter that into the autopilot yourself, and ensure it’s in a mode that allows it to change flight level.

People mistakenly think that pilots don’t do anything. But in fact, aviation is extremely demanding, with tons of tasks that must be done without fail. And so offloading some of the workload to the autopilot makes total sense. But pilots also want to fly. They didn’t do all that training and spend years earning poverty wages as junior pilots only to then sit in the cockpit and do nothing. So often, they do many things manually that they could automate. And other things, like takeoffs and landings, are never done automated, even if the hardware and software is present. They’re there as backup systems if, for instance, a pilot is incapacitated and the copilot is also occupied with some emergency and needs to offload a task.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on March 14, 2019, 02:24:06 am
Though auto-takeoff and autoland (in addition to the cruise autopilot) have actually existed for many decades, making it theoretically possible for an aircraft to have every phase of flight automated, this isn’t really done in practice.

Autopilot isn’t a single thing. It’s an umbrella term for dozens of discrete automation functions that can be used all at once, or none at all, or in any combination. So things like auto-navigation (automatic turns), auto level (maintain flight level), autothrottle (maintain speed), auto brake (on landing) etc. But tons more are automatic safeguards, like stall prevention.
Yep, it's called FMS; Flight Management System.
Usually engaged/disengaged just after takeoff and just before landing and depending on guidance systems and weather conditions disengagement might be as low as 10's of feet above the runway.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 14, 2019, 03:31:29 am
Not mentioned here, but there have been a few other similar airdata computer/autopilot plunge accidents (bad data=bad programmed response); such as

A330-200  Air France 447 crashed off the coast of Brazil
A330-300 Qantas 72 which diverted to Learmonth


One of the points the proponents of Boeing AC have made relative to Airbus is that Boeing AC permitted the pilots greater control over the plane whereas Airbus went full in with the all-seeing all-controlling control system.  What these latest accidents in Boeing planes suggests is that Boeing doesn't appear to have a leg to stand on in this respect -- at least not any more.  It's too soon to say of the Amazon plane that crashed last week was also due to the computer doing something the crew either didn't comprehend or couldn't fight.  If the 767 crash winds up being a similar computer control issue then Boeing could be toast and i'm 100% serious about that as far as commercial aviation is concerned.  The last 20-30 years has seen software come to dominate the tech world where hardware used to, but sometimes the software types don't know as much as they think they do or they think pilots are so stupid they need to be kept on a leash. 


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Homer J Simpson on March 14, 2019, 04:31:23 am
https://www.youtube.com/watch?v=3jGNn2T_gyU (https://www.youtube.com/watch?v=3jGNn2T_gyU)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 14, 2019, 04:41:14 am
One of the points the proponents of Boeing AC have made relative to Airbus is that Boeing AC permitted the pilots greater control over the plane whereas Airbus went full in with the all-seeing all-controlling control system.  What these latest accidents in Boeing planes suggests is that Boeing doesn't appear to have a leg to stand on in this respect -- at least not any more.  It's too soon to say of the Amazon plane that crashed last week was also due to the computer doing something the crew either didn't comprehend or couldn't fight.  If the 767 crash winds up being a similar computer control issue then Boeing could be toast and i'm 100% serious about that as far as commercial aviation is concerned.  The last 20-30 years has seen software come to dominate the tech world where hardware used to, but sometimes the software types don't know as much as they think they do or they think pilots are so stupid they need to be kept on a leash. 

A classic example of this is the Therac-25 incidents. https://web.stanford.edu/class/cs240/old/sp2014/readings/therac-25.pdf
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 14, 2019, 09:01:18 am
The last 20-30 years has seen software come to dominate the tech world where hardware used to, but sometimes the software types don't know as much as they think they do or they think pilots are so stupid they need to be kept on a leash.
This is nonsense. The "software guys" do not make the use cases, requirements and safety concerned issues.
There should be a product owner, (sub)system architects and system engineers that can translate the use cases to requirements and that should involve safety features including redundant systems and fallback scenario's.
Then there should be an elaborate testing phase where all systems and software routines are rigurously tested, esp the safety critical ones with high impact, they should be continuously tested in simulators.
For a modern airplane I can imagine this would take years. Why do you think the software update took so long? It needs to be restested the whole shabang.
In any good business this is in place esp. where safety and reliability is a major issue.

BTW many accidents in the past where hardware related, a bolt that was made from the wrong steel and broke off, a sensor that was cluttered, so to say software is worse than hardware.... they both can be cause for an accident.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 14, 2019, 10:30:27 am
Boeing Statement On 737 MAX Software Enhancement
http://aero-news.net/index.cfm?do=main.textpost&ID=78526990-A846-4929-8D11-9D3C0FDD9DE3 (http://aero-news.net/index.cfm?do=main.textpost&ID=78526990-A846-4929-8D11-9D3C0FDD9DE3)
Quote
For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.
[...]
Boeing’s 737 MAX Flight Crew Operations Manual (FCOM) already outlines an existing procedure to safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor. The pilot will always be able to override the flight control law using electric trim or manual trim. In addition, it can be controlled through the use of the existing runaway stabilizer procedure as reinforced in the Operations Manual Bulletin (OMB) issued on Nov. 6, 2018

Emergency Airworthiness Directive (AD) 2018-23-51 is sent to owners and operators of The Boeing Company Model 737-8 and -9 airplanes.
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument)
Quote
This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.
[...]
Runaway Stabilizer
Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.
Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.
In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.
An erroneous AOA input can cause some or all of the following indications and effects:
•   Continuous or intermittent stick shaker on the affected side only.
•   Minimum speed bar (red and black) on the affected side only.
•   Increasing nose down control forces.
•   IAS DISAGREE alert.
•   ALT DISAGREE alert.
•   AOA DISAGREE alert (if the option is installed).
•   FEEL DIFF PRESS light.
•   Autopilot may disengage.
•   Inability to engage autopilot.
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: langwadt on March 14, 2019, 02:42:20 pm
Not mentioned here, but there have been a few other similar airdata computer/autopilot plunge accidents (bad data=bad programmed response); such as

A330-200  Air France 447 crashed off the coast of Brazil

I'm not sure you can blame that on the computer, the computer switched to alternate law when it didn't believe the sensor input,
leaving the controls to the pilots with the task of not crashing a perfectly functional plane flying at 38000 feet
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on March 14, 2019, 03:23:03 pm
Not mentioned here, but there have been a few other similar airdata computer/autopilot plunge accidents (bad data=bad programmed response); such as

A330-200  Air France 447 crashed off the coast of Brazil

I'm not sure you can blame that on the computer, the computer switched to alternate law when it didn't believe the sensor input,
leaving the controls to the pilots with the task of not crashing a perfectly functional plane flying at 38000 feet

And the pilots then did the same dumb thing that the auto-pilot appears to have done on the 737-MAX aircraft, pushed the nose down to gain speed....
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: newbrain on March 14, 2019, 03:57:04 pm
And the pilots then did the same dumb thing that the auto-pilot appears to have done on the 737-MAX aircraft, pushed the nose down to gain speed....
Had to check, because that's not what I remembered:
In fact, they did the exact opposite. Had they put the nose down, instead of up, the plane would (probably) not have crashed.
From wikipedia (https://en.wikipedia.org/wiki/Air_France_Flight_447):
Quote
From there until the end of the flight, the angle of attack never dropped below 35 degrees.

Having flown with Ethiopian airlines twice a month for several years, I was quite shocked by this disaster.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on March 14, 2019, 05:44:48 pm
And the pilots then did the same dumb thing that the auto-pilot appears to have done on the 737-MAX aircraft, pushed the nose down to gain speed....
Had to check, because that's not what I remembered:
In fact, they did the exact opposite. Had they put the nose down, instead of up, the plane would (probably) not have crashed.
From wikipedia (https://en.wikipedia.org/wiki/Air_France_Flight_447):
Quote
From there until the end of the flight, the angle of attack never dropped below 35 degrees.

Having flown with Ethiopian airlines twice a month for several years, I was quite shocked by this disaster.

Sorry, I got it backwards, but it was still incorrect airdata info that led to (in this case) pilots doing the wrong thing.  I do remember being told "If you lost all instruments - 75% power, keep it level - and it will fly"

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: jmelson on March 14, 2019, 07:46:39 pm
And the pilots then did the same dumb thing that the auto-pilot appears to have done on the 737-MAX aircraft, pushed the nose down to gain speed....
NO NO!  That't the PROBLEM!  They SHOULD have pushed the stick forward, to exit the stall and get flying.  But, at least ONE pilot held the stick full back until they hit the water!  The other pilot was pushing full forward, which was what was needed to break out of the stall.  But, because these sticks are not coupled and do not have any force feedback, the pilots did not know what the other one was doing.

Something that may have confused them is the Airbus suppresses the stall warning below 70 knots airspeed, so you don't have the horn blaring during landing.
But, this caused the horn to start blaring each time they began to escape from the stall.  Somehow the one pilot believed that by pulling back on his stick and keeping the horn from sounding, he was ESCAPING from the stall.  Total lack of understanding the systems.

Jon
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 14, 2019, 07:53:40 pm
  Total lack of understanding the systems.
Or are the systems designed ambiguous ?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Dundarave on March 14, 2019, 11:50:37 pm

Emergency Airworthiness Directive (AD) 2018-23-51 is sent to owners and operators of The Boeing Company Model 737-8 and -9 airplanes.
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument)
This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.
[...]
Runaway Stabilizer
Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.
Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.
In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.
An erroneous AOA input can cause some or all of the following indications and effects:
•   Continuous or intermittent stick shaker on the affected side only.
•   Minimum speed bar (red and black) on the affected side only.
•   Increasing nose down control forces.
•   IAS DISAGREE alert.
•   ALT DISAGREE alert.
•   AOA DISAGREE alert (if the option is installed).
•   FEEL DIFF PRESS light.
•   Autopilot may disengage.
•   Inability to engage autopilot.
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

That's quite the software "workaround" for when the aircraft hardware (i.e. the angle-of-attack sensors, etc.) goes whacko.  I wouldn't want to be reading those instructions for the first time while the plane is trying its damndest to dive nose-first with "possible impact with terrain".

I'd be thinking that the recovery maneuvers as described above would need to be a simulator-based exercise repeated until it was thoroughly drilled in.  No time for "is the aircraft doing that thing with the bad AOA sensor or is something else wrong?" discussions in the cockpit.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 15, 2019, 12:38:31 am

Emergency Airworthiness Directive (AD) 2018-23-51 is sent to owners and operators of The Boeing Company Model 737-8 and -9 airplanes.
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument)
This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.
[...]
Runaway Stabilizer
Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.
Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.
In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.
An erroneous AOA input can cause some or all of the following indications and effects:
•   Continuous or intermittent stick shaker on the affected side only.
•   Minimum speed bar (red and black) on the affected side only.
•   Increasing nose down control forces.
•   IAS DISAGREE alert.
•   ALT DISAGREE alert.
•   AOA DISAGREE alert (if the option is installed).
•   FEEL DIFF PRESS light.
•   Autopilot may disengage.
•   Inability to engage autopilot.
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

That's quite the software "workaround" for when the aircraft hardware (i.e. the angle-of-attack sensors, etc.) goes whacko.  I wouldn't want to be reading those instructions for the first time while the plane is trying its damndest to dive nose-first with "possible impact with terrain".

I'd be thinking that the recovery maneuvers as described above would need to be a simulator-based exercise repeated until it was thoroughly drilled in.  No time for "is the aircraft doing that thing with the bad AOA sensor or is something else wrong?" discussions in the cockpit.

It's not a software workaround, it's a procedural workaround. The procedure itself is actually pretty simple (STAB TRIM CUTOUT switches to CUTOUT, adjust trim by hand wheel). Most of the above is explanation, not procedure.

The software workaround is what Boeing is currently developing.

Any affected pilot reading those instructions for the first time during an event has failed their duty as a pilot, and their employer has failed at training. Stuff like this is not optional reading material.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: langwadt on March 15, 2019, 12:42:37 am

Emergency Airworthiness Directive (AD) 2018-23-51 is sent to owners and operators of The Boeing Company Model 737-8 and -9 airplanes.
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83EC7F95F3E5BFBD8625833E0070A070?OpenDocument)
This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.
[...]
Runaway Stabilizer
Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.
Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.
In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.
An erroneous AOA input can cause some or all of the following indications and effects:
•   Continuous or intermittent stick shaker on the affected side only.
•   Minimum speed bar (red and black) on the affected side only.
•   Increasing nose down control forces.
•   IAS DISAGREE alert.
•   ALT DISAGREE alert.
•   AOA DISAGREE alert (if the option is installed).
•   FEEL DIFF PRESS light.
•   Autopilot may disengage.
•   Inability to engage autopilot.
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

That's quite the software "workaround" for when the aircraft hardware (i.e. the angle-of-attack sensors, etc.) goes whacko.  I wouldn't want to be reading those instructions for the first time while the plane is trying its damndest to dive nose-first with "possible impact with terrain".

I'd be thinking that the recovery maneuvers as described above would need to be a simulator-based exercise repeated until it was thoroughly drilled in.  No time for "is the aircraft doing that thing with the bad AOA sensor or is something else wrong?" discussions in the cockpit.

I read somewhere that US airlines have a custom software for the Max that permanently displays the AOA for MCAS on the main display, I  guess so
the pilots can instantly see if the value makes sense

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Dundarave on March 15, 2019, 01:15:19 am

It's not a software workaround, it's a procedural workaround. The procedure itself is actually pretty simple (STAB TRIM CUTOUT switches to CUTOUT, adjust trim by hand wheel). Most of the above is explanation, not procedure.

The software workaround is what Boeing is currently developing.

Any affected pilot reading those instructions for the first time during an event has failed their duty as a pilot, and their employer has failed at training. Stuff like this is not optional reading material.

I suppose the type of "workaround" is a semantic argument, but I'd say that if mission-critical system software such as this can't correctly handle faulty inputs like a defective AOA sensor, and instead needs timely and critical human intervention to avoid a disaster, then there's something wrong with the software, and the efforts needed to do the job that software should be doing constitute a workaround.

I would think that what Boeing is currently developing would be software that does what it should, and not simply "workaround" what it has already written.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 15, 2019, 02:12:19 am
A software workaround is when your software is changed to handle a failure in some other system.

So when hardware fails, whatever the software does to compensate is, by definition, a workaround -- something designed to work as well as possible until the failing system can be repaired. There are many other workarounds designed into avionics software, as there are many systems that have the potential to fail. This is one that just wasn't done right the first time around. And got through testing and review.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 15, 2019, 02:17:41 am
News reports suggest that part of the reason they were able to tie the two crashes together and point towards both crashes having a similar/same cause and before they had the FDR or CVR was the position of the horizontal stabilizer jack screw.  If the plane was forced down by MCAS or similar the jack screw would be wound up towards one end of travel -- the end forcing the plane down.  That, on top of the refined GPS altitude data pointing to a bucking bronco ride into the ground is pretty clear evidence that Lionair and this crash have a common cause.

The French now have the recorders and hopefully we'll get a preliminary readout on them tomorrow or soon and I would be very interested to know what the AOA, altitude and airspeed indications were and what differences, if any, one side had versus the other.


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 15, 2019, 03:26:56 am
That, on top of the refined GPS altitude data pointing to a bucking bronco ride into the ground is pretty clear evidence that Lionair and this crash have a common cause.

That is absolutely incorrect.

At this point, you cannot say they have a common cause.  What you can say is that they have an apparently similar symptom.

This is one of the specific areas of objectivity of crash analysts that cannot be understated ... and it is why only the Media are making such a big noise with hypotheses.  You can never allow previous incidents to influence a current investigation or you could end up with "scenario fulfillment" instead of an accurate, unbiased report on what actually happened.

"Feel good" answers don't stop planes falling out of the sky in the future.  Only ones derived from meticulous scrutiny by objective, trained staff following a rigorous process will.


This is the reason why I will not speculate on events such as these.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 15, 2019, 04:33:01 am
The similar time-constant apparently correlates to the anti-stall automation at work.

Even to a layman, Boeing's MCAS implementation is shit, even if it's not a factor in the ET 302 crash.
I can't see why we defend the mighty Boeing and blame the pilots for not executing some manual sequence from hell.

People say Boeing's product-development cycle cannot move this fast (to compete with Airbus) and continue to make safe aircraft. Using undocumented automation to cover up a handling problem, then sneak it through FAA approvals is terrible. There is huge money at stake here, Boeing's stock losing $28B in market cap and there are $600B of orders in the books.

Kudos to Ethiopian Airlines for not giving the black boxes over to US authorities, and instead having France's BEA do the investigation. I have no confidence in the FAA after insisting the aircraft is airworthy despite the rest of the world grounding the aircraft, and how MCAS made it through certification in the first place.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 15, 2019, 04:54:14 am
That, on top of the refined GPS altitude data pointing to a bucking bronco ride into the ground is pretty clear evidence that Lionair and this crash have a common cause.

That is absolutely incorrect.

At this point, you cannot say they have a common cause.  What you can say is that they have an apparently similar symptom.

This is one of the specific areas of objectivity of crash analysts that cannot be understated ... and it is why only the Media are making such a big noise with hypotheses.  You can never allow previous incidents to influence a current investigation or you could end up with "scenario fulfillment" instead of an accurate, unbiased report on what actually happened.

"Feel good" answers don't stop planes falling out of the sky in the future.  Only ones derived from meticulous scrutiny by objective, trained staff following a rigorous process will.


This is the reason why I will not speculate on events such as these.


Oh please, while there is more to learn from the FDR and CVR and it is possible the cause will point elsewhere, the idea that the forensic data from the crashed plane and the data from the broadcast GPS data are meaningless is, well, laughable.  The fact is, the results of those aforementioned two datapoints are that dozens of airlines and aviation agencies including the FAA grounded the 737 Max, before the data from the FDR and CVR were even downloaded, and even the manufacturer, Boeing, was compelled to call for the grounding, prior to the analysis of the CVR and FDR, makes it crystal clear that the consensus view of the experts is that the similarities are sufficient to call for grounding.  And, while it is possible that analysis of the recorders will clear this 737 Max from a MCAS or similar automation problem, the data they have already was enough to make a call that will cost billions to numerous airline and quite possibly many billions for Boeing.  Not to mention the unavoidable impact that this grounding will have on millions of airline passengers and quite possibly for months or longer.  Perhaps try and be a bit less sanctimonious!


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 15, 2019, 06:09:41 am
Really?

I never said that the fallout for Boeing wouldn't be significant - no matter what the outcome.  So don't try throwing that in my face.

All I AM saying is that ANYBODY who has "determined" the cause of this accident at this point in time is not basing it on all the facts.

You MAY be right - and if it does turn out that you are, that still does not give you any right to be sanctimonious about your guessing at this stage.


Just pile on with the Media circus.  You'll enjoy their company.

I'll wait.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 15, 2019, 07:41:33 am
But Brumby, the data we already have is very telling, isn't it?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 15, 2019, 07:53:19 am
I agree with Brumby, if you do not have all the information it becomes speculation.

The grounding of the plane AFAIK is foremost taken because it is a new plane AND two brand new planes crashed within a half year.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 15, 2019, 08:08:38 am
The grounding of the plane AFAIK is foremost taken because it is a new plane AND two brand new planes crashed within a half year.

... apparently in the same way and for the same reason. No?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 15, 2019, 11:11:15 am
But Brumby, the data we already have is very telling, isn't it?

It does lend itself to the conclusions the Media is jumping to with great haste.  As I said, it may be that those conclusions could be close to the truth - but the information available is by no means sufficient to start drawing definitive conclusions at this time.


... apparently in the same way and for the same reason. No?

Even that is a little too far for my liking - but it does acknowledge an element of uncertainty, which is appropriate.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: langwadt on March 15, 2019, 11:39:34 am
That, on top of the refined GPS altitude data pointing to a bucking bronco ride into the ground is pretty clear evidence that Lionair and this crash have a common cause.

That is absolutely incorrect.

At this point, you cannot say they have a common cause.  What you can say is that they have an apparently similar symptom.

This is one of the specific areas of objectivity of crash analysts that cannot be understated ... and it is why only the Media are making such a big noise with hypotheses.  You can never allow previous incidents to influence a current investigation or you could end up with "scenario fulfillment" instead of an accurate, unbiased report on what actually happened.

In one of the "Air Crash Investigation" episodes one of the investigators said they internationally do not watch any kind of news
before examining the crash site

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 15, 2019, 11:44:25 am
The grounding of the plane AFAIK is foremost taken because it is a new plane AND two brand new planes crashed within a half year.
... apparently in the same way and for the same reason. No? 
You can not talke about "The same reason" while the cause is not 100% determined and investigation is not completed IMO.

I would go as far as that two new planes crash within a limited timeframe without obvious external cause.

(If there was a second plane involved that crashed into the plane or that there was extreme weather like a tornado etc. that would IMO be an external cause)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 15, 2019, 11:50:55 am
That, on top of the refined GPS altitude data pointing to a bucking bronco ride into the ground is pretty clear evidence that Lionair and this crash have a common cause.

That is absolutely incorrect.

At this point, you cannot say they have a common cause.  What you can say is that they have an apparently similar symptom.

This is one of the specific areas of objectivity of crash analysts that cannot be understated ... and it is why only the Media are making such a big noise with hypotheses.  You can never allow previous incidents to influence a current investigation or you could end up with "scenario fulfillment" instead of an accurate, unbiased report on what actually happened.

In one of the "Air Crash Investigation" episodes one of the investigators said they internationally do not watch any kind of news
before examining the crash site
Yep.

And also, there have been cases where crash investigators announced the cause prematurely, and it turned out that their initial suspicion was wrong.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 15, 2019, 11:54:15 am
Kudos to Ethiopian Airlines for not giving the black boxes over to US authorities, and instead having France's BEA do the investigation. I have no confidence in the FAA after insisting the aircraft is airworthy despite the rest of the world grounding the aircraft, and how MCAS made it through certification in the first place.
Your mistrust is misplaced, then, because the FAA isn't responsible for crash investigations at all. Black boxes are sent to the NTSB, a completely different arm of government that is independent from the FAA. (It doesn't make rules, it produces crash reports and recommendations, which regulatory agencies like the FAA, as well as manufacturers, can choose to follow, or not.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: TheNewLab on March 15, 2019, 12:13:52 pm
Kudos to Ethiopian Airlines for not giving the black boxes over to US authorities, and instead having France's BEA do the investigation. I have no confidence in the FAA after insisting the aircraft is airworthy despite the rest of the world grounding the aircraft, and how MCAS made it through certification in the first place.
Your mistrust is misplaced, then, because the FAA isn't responsible for crash investigations at all. Black boxes are sent to the NTSB, a completely different arm of government that is independent from the FAA. (It doesn't make rules, it produces crash reports and recommendations, which regulatory agencies like the FAA, as well as manufacturers, can choose to follow, or not.)

Correct.
Grew up around airline and aviation people.  The NTSB is world-class. Their labs and investigative abilities set the standard
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MasterTech on March 15, 2019, 12:46:35 pm

Correct.
Grew up around airline and aviation people.  The NTSB is world-class. Their labs and investigative abilities set the standard

Agreed, but Nasa is also world-class and political/administrative pressures made the Columbia accident happen.

So given this is not a cessna or learjet accident investigation, and given the interests are extremely high due to uncalculable economic losses a bit of caution regarding who investigates this is understandable

Also, the plane was configured to crash dive, https://www.bloomberg.com/news/articles/2019-03-15/piece-found-in-crash-wreckage-said-to-show-jet-was-set-to-dive (https://www.bloomberg.com/news/articles/2019-03-15/piece-found-in-crash-wreckage-said-to-show-jet-was-set-to-dive)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 15, 2019, 02:44:32 pm
Grew up around airline and aviation people.  The NTSB is world-class. Their labs and investigative abilities set the standard

All NTSB investigations go like this: if the pilot died in the accident, it was a pilot error ~ 100% of the times, if he's alive, 50/50 chance of he being the culprit. Just watch the "Mayday" series and do the math.

Another example: we've been flying in 747 Jumbos with faulty cargo door lock mechanisms for decades... and they knew that. It was the father of a victim who had to demonstrate that, because the NTSB was hiding the truth:

https://en.wikipedia.org/wiki/United_Airlines_Flight_811#Personal_investigation_and_later_developments

I for one am glad the ET 302 black box wasn't sent to the USA, it's not a good thing when the judge is a part.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 15, 2019, 03:20:45 pm
https://www.sapromo.com/737-max-crash-a-jackscrew-screwed-up/47577 (https://www.sapromo.com/737-max-crash-a-jackscrew-screwed-up/47577)

Quote
MyBroadband.co.za reports that the US’s Federal Aviation Administration chief Daniel Elwell earlier this week cited unspecified evidence found at the crash scene as part of the justification for the agency to reverse course and temporarily halt flights of Boeing’s largest selling aircraft. Up until then, American regulators had held off as nation after nation had grounded the plane, Boeing’s best-selling jet model.

The piece of evidence was a so-called jackscrew, used to set the trim that raises and lowers the plane’s nose, according to the person, who requested anonymity to discuss the inquiry.

A preliminary review of the device and how it was configured at the time of the crash indicated that it was set to push down the nose, according to the person, who wasn’t authorized to speak publicly about the investigation.

The jackscrew, combined with a newly obtained satellite flight track of the plane, convinced the FAA that there were similarities to the Oct. 29 crash of the same Max model off the coast of Indonesia. In the earlier accident, a safety feature on the Boeing aircraft was repeatedly trying to put the plane into a dive as a result of a malfunction.

All 157 people aboard Ethiopian Airlines Flight 302 died early Sunday shortly after the plane took off. The pilot reported an unspecified problem and was trying to return to the airport. The plane crashed near Addis Ababa, Ethiopia’s capital. The plane’s crash-proof recorders have been sent to France to be analyzed.

The discovery of the jackscrew was earlier reported by NBC News.

One plus one...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 15, 2019, 05:40:37 pm
Kudos to Ethiopian Airlines for not giving the black boxes over to US authorities, and instead having France's BEA do the investigation. I have no confidence in the FAA after insisting the aircraft is airworthy despite the rest of the world grounding the aircraft, and how MCAS made it through certification in the first place.
Your mistrust is misplaced, then, because the FAA isn't responsible for crash investigations at all. Black boxes are sent to the NTSB, a completely different arm of government that is independent from the FAA. (It doesn't make rules, it produces crash reports and recommendations, which regulatory agencies like the FAA, as well as manufacturers, can choose to follow, or not.)

I'm not clear then on what US agency Ethiopian Airlines is blowing off, by getting France's BEA to do the crash investigation.
The NTSB can make recommendations to the FAA, who may or may not choose to adopt them.

Who is driving the software update to the MCAS? It should not be Boeing, as their processes already failed implementing it, and not the FAA for wrongly certifying it.
As an outcome of the Lion Air crash investigation, I assume some agency recommended MCAS changes- which were not rolled out and of course they would make Boeing liable.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 15, 2019, 06:33:48 pm
As an outcome of the Lion Air crash investigation, I assume some agency recommended MCAS changes- which were not rolled out and of course they would make Boeing liable.
What outcome? The accident happened last October, one black box was found in November and the other one in January. Plus both the FAA and NTSB mostly stopped working for a month because Trump shut down the government. NTSB is thorough and professional and doesn't jump to conclusions like most of us, but the price is time. Expect their report and recommendations in a year or so.
It'll show up here: https://www.ntsb.gov/investigations/AccidentReports/Pages/aviation.aspx (https://www.ntsb.gov/investigations/AccidentReports/Pages/aviation.aspx)
All we have so far is some data releases. And we've yet to hear what the cockpit recorder said at all.

The FAA, on the other hand, can choose to react much more quickly with Airworthiness Directives, based on events or on recommendations from aircraft manufacturers.

As for the software process, I already mentioned that earlier in the thread. It's not quick, even if you want it to be, testing is required, and the FAA does have to certify it. A few months is really fast turnaround.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: raptor1956 on March 15, 2019, 07:40:42 pm
Really?

I never said that the fallout for Boeing wouldn't be significant - no matter what the outcome.  So don't try throwing that in my face.

All I AM saying is that ANYBODY who has "determined" the cause of this accident at this point in time is not basing it on all the facts.

You MAY be right - and if it does turn out that you are, that still does not give you any right to be sanctimonious about your guessing at this stage.


Just pile on with the Media circus.  You'll enjoy their company.

I'll wait.


Again with the sanctimonious nonsense -- at no time did I declare the the accident was definitely this that or anything else -- you really should pull your head out of you anally retentive a$$!

The investigators, not me, have reviewed the crash scene and in combination with the broadcast GPS data have determined the crash is sufficiently similar to the Lionair crash that it warranted grounding the 737 Max.  IT WAS NOT I THAT DID THAT DIP SH!T!


Brian
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: imo on March 15, 2019, 08:41:39 pm
NY Times https://www.nytimes.com/2019/03/15/business/boeing-ethiopian-crash.html (https://www.nytimes.com/2019/03/15/business/boeing-ethiopian-crash.html)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Simon on March 15, 2019, 09:45:57 pm
Really?

I never said that the fallout for Boeing wouldn't be significant - no matter what the outcome.  So don't try throwing that in my face.

All I AM saying is that ANYBODY who has "determined" the cause of this accident at this point in time is not basing it on all the facts.

You MAY be right - and if it does turn out that you are, that still does not give you any right to be sanctimonious about your guessing at this stage.


Just pile on with the Media circus.  You'll enjoy their company.

I'll wait.


Again with the sanctimonious nonsense -- at no time did I declare the the accident was definitely this that or anything else -- you really should pull your head out of you anally retentive a$$!

The investigators, not me, have reviewed the crash scene and in combination with the broadcast GPS data have determined the crash is sufficiently similar to the Lionair crash that it warranted grounding the 737 Max.  IT WAS NOT I THAT DID THAT DIP SH!T!


Brian

Calm down.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 15, 2019, 10:11:47 pm
NY Times https://www.nytimes.com/2019/03/15/business/boeing-ethiopian-crash.html (https://www.nytimes.com/2019/03/15/business/boeing-ethiopian-crash.html)

Ethiopian 737-8 Max UPDATE:
https://www.youtube.com/watch?v=AgkmJ1U2M_Q (https://www.youtube.com/watch?v=AgkmJ1U2M_Q)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 15, 2019, 11:12:42 pm
Raptor1956:
Just wanted to say that I came to this thread, seemingly only the other day. I had read some of the recent revelations about the MCAS and the trim/elevator and the elevation graph, and I found this paints one very clear picture of what likely happened in both of these crashes.

So when I saw this megathread, I was curious to see what the EEV hive mind thought, and I read more or less every single post from the beginning, seemingly for the first time. Curiously, though, I found I had thanked one of your earlier posts, lol. So I had visited this thread, at least once, before. And I recognized your early posts to be among the most rational and logical and comprehensive... without any innate bias. And as it turns out, I would say that hindsight will more than likely show that you were the right horse to bet on.

I just wanted you to know your input to this thread has been appreciated by me and surely by others. I hope you don't get caught up in semantic BS from latecomers to the thread. It is obvious from the thread history that you are not making assumptions at any stage in the thread. Even prior to the more recent relevations, your thought process and conjecture was unimpeachable and insightful, IMO, as a non-pilot.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 16, 2019, 01:05:44 am
In one of the "Air Crash Investigation" episodes one of the investigators said they internationally do not watch any kind of news before examining the crash site
Yes the fake news media would pollute any investigation.

Boing says MCAS soft fix in coming weeks.
https://www.youtube.com/watch?v=VRx8BBQyX10 (https://www.youtube.com/watch?v=VRx8BBQyX10)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 16, 2019, 05:50:13 am
But, because these sticks are not coupled and do not have any force feedback, the pilots did not know what the other one was doing.

This is something that has always struck me as an absolutely stupid design. If the plane has two sticks, they should absolutely be mechanically linked together, or only one set of controls should be active at a time, with a very obvious indication of which is active. I never liked the sidestick arrangement anyway, it just looks wrong, and seems like it would be awkward.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Simon on March 16, 2019, 08:21:57 am
In one of the "Air Crash Investigation" episodes one of the investigators said they internationally do not watch any kind of news before examining the crash site
Yes the fake news media would pollute any investigation.



Ordinary trials in the UK have been thrown out because just 1 member of the jury decided to go detectiving for themselves rather than rely solely on the evidence presented in court.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 16, 2019, 08:24:26 am
From the video at #376:
"[...] The software fix is going to require this flight control system to rely on data from TWO sensors, it previously was only dependent on one [...]"

Really? The MCAS is reading only one sensor? That seems unbelievable to me. The engineers at Boeing no more no less, should have known better.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Simon on March 16, 2019, 08:27:09 am
safty critical with one sensor? ouch! idealy you want 3 so you know who to trust.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 16, 2019, 08:34:52 am
safty critical with one sensor? ouch! idealy you want 3 so you know who to trust.

Even the accelerator pedal of my 1998 ford focus has three separate potentiometers!

Is this (in bold, below) a weasel-ish way of saying "from now on we're going to read the second AoA sensor too"?

Boeing Statement On 737 MAX Software Enhancement
http://aero-news.net/index.cfm?do=main.textpost&ID=78526990-A846-4929-8D11-9D3C0FDD9DE3 (http://aero-news.net/index.cfm?do=main.textpost&ID=78526990-A846-4929-8D11-9D3C0FDD9DE3)
Quote
For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.
[...]
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: donotdespisethesnake on March 16, 2019, 08:37:38 am
From the video at #376:
"[...] The software fix is going to require this flight control system to rely on data from TWO sensors, it previously was only dependent on one [...]"

Really? The MCAS is reading only one sensor? That seems unbelievable to me. The engineers at Boeing no more no less, should have known better.

I think the idea will be to cross-check the two sensors for agreement, if they disagree then disable MCAS and issue a warning to the pilots.

While the engineers at Boeing should (and probably do) know better, they are overruled by finance and marketing these days.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 16, 2019, 08:46:35 am
I think the idea will be to cross-check the two sensors for agreement, if they disagree then disable MCAS and issue a warning to the pilots.

From reply #339:
Quote
•   IAS DISAGREE alert.
•   ALT DISAGREE alert.
•   AOA DISAGREE alert (if the option is installed).
•   FEEL DIFF PRESS light.

AoA DISAGREE is (was?) an option!  |O

But then, the second AoA sensor what for was there? For decoration?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: donotdespisethesnake on March 16, 2019, 09:07:09 am
I think the idea will be to cross-check the two sensors for agreement, if they disagree then disable MCAS and issue a warning to the pilots.

From reply #339:
Quote
•   IAS DISAGREE alert.
•   ALT DISAGREE alert.
•   AOA DISAGREE alert (if the option is installed).
•   FEEL DIFF PRESS light.

AoA DISAGREE is (was?) an option!  |O

But then, the second AoA what for was there? For decoration?

The second sensor is redundant, I think the sensors are fed to each seat, similar to how other controls such as altimeter. I.e. captain seat gets sensor input from LH sensors, FO seat gets info from RH sensors. The normal CRM would have the pilots determine the faulty sensor and ignore it. Unfortunately CRM is often lacking in upset situations. In this case, if they don't quickly identify the need to disable electric trim it is too late.

The AoA DISAGREE is an option few airlines have taken. It's up to the pilots to see it then disable electric trim (which also prevents MCAS moving the stabilizer).

I think the MCAS can currently only take one AoA or the other, so the fix would be to use both, or at least use the AoA DISAGREE signal to automatically disable MCAS, presumably there needs to be another alert to indicate MCAS Inoperative.

I'm afraid to say it's a set of bodges to cater for the original decision to add bigger engines, AND retain 737 flight characteristics so that minimal type conversion is required for the pilots.

Unfortunately, I see the same trend in other industries. Marketing, finance are allowed to override proper engineering. The question is always "how much will it cost?", and not "is the quality right?"
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 16, 2019, 01:59:00 pm
^ I don't get how this is even a cost issue. It seems much more like an oversight.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: donotdespisethesnake on March 16, 2019, 06:27:24 pm
^ I don't get how this is even a cost issue. It seems much more like an oversight.

Because the 737 MAX grandfathers certification and type training from the 737 Classic. If Boeing change the design significantly, it needs a whole new certification - expensive and time consuming. If the flight characteristics change, it means new type training for the pilots, so operators need to be spend money on training, and the pilots need to get type certificate.

Boeing wanted to get a plane into production quickly, because Airbus was outselling them by a wide margin.

By telling regulators and operators that "the MAX can be treated the same as the classic", Boeing took a big shortcut compared to designing a new airframe. It seems that gamble created a major flaw.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 16, 2019, 08:43:00 pm
It's a Boeing design error and the S/W patch allowing "the option" of using two sensors stinks of cover-up. AOA DISAGREE alert indicator is also an "option"?!  :palm:

Using two sensors is still shitty because you have now doubled the probability of MCAS failure due to a sensor failure.
Multiple sensors iced up for the AF447 disaster. Would MCAS register a discrepancy with two sensors reading similar yet both are out to lunch?
I'll repeat the old adage "with two clocks you can never know the correct time". This MCAS system is never going to be stellar, even adding a third (sensor) opinion because the other pair can malfunction. It's just getting a slightly lower probability of failure, this is all Boeing can accomplish. Unless there was a gross S/W bug that is being fixed too.

In other industries with safety-critical design, you do fault-tree analysis and FMEDA to ensure you have coverage of a sensor problem, among other scenarios.
Clearly, Boeing bungled this and is showing a repeat bungle with their hasty "software fix" that cannot meet basic functional safety requirements even after piling on the algorithm smartness.
I've seen this before - a bad design safety-critical system is out there, sold in numbers and a corporation has a massive panic to fix it ASAP without changing any hardware.
Adding complex S/W algorithms (which can never be proven correct) is very dangerous.

Then I read this: (http://www.b737.org.uk/mcas.htm)
"MCAS is implemented within the two Flight Control Computers (FCCs). The Left FCC uses the Left AOA sensor for MCAS and the Right FCC uses the Right AOA sensor for MCAS. Only one FCC operates at a time to provide MCAS commands. With electrical power to the FCCs maintained, the unit that provides MCAS changes between flights. In this manner, the AOA sensor that is used for MCAS changes with each flight."

How do you come up with something so stupid?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Simon on March 16, 2019, 08:50:26 pm
I assumed that for a safety critical system you measure everything with 3 sensors, should one fail you can identify it is the failed one as two measurements still agree and you flaf the faulty sensor.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 16, 2019, 09:21:58 pm
On the horizon i can see a large number of relatives preparing to sue Boing.
Quote
Boeing have been working on a software modification to MCAS since the Lion Air accident. Unfortunately although originally due for release in January it has still not been released due to both engineering challenges and differences of opinion among some federal and company safety experts over how extensive the changes should be. Apparently there have been discussions about potentially adding enhanced pilot training and possibly mandatory cockpit alerts to the package. There also has been consideration of more-sweeping design changes that would prevent faulty signals from a single sensor from touching off the automated stall-prevention system.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 16, 2019, 10:39:51 pm
https://www.youtube.com/watch?v=RyeqeqSNSgQ (https://www.youtube.com/watch?v=RyeqeqSNSgQ)

Somebody remind me why MCAS is even needed?
This 737 max 8 is presumably empty, but none the less, wow an impressive climb.

ET302 took off like a bat out of hell, hard vertical climb for the first few seconds after takeoff so I wonder if a sensor was not working right from the start.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: chickenHeadKnob on March 17, 2019, 12:29:21 am
Somebody remind me why MCAS is even needed?
This 737 max 8 is presumably empty, but none the less, wow an impressive climb.

ET302 took off like a bat out of hell, hard vertical climb for the first few seconds after takeoff so I wonder if a sensor was not working right from the start.

The angle of attack sensors don't measure the angle with the ground or horizon, rather they measure the relative angle of the airflow to the center line of the aircraft. So if the aircraft is moving fast enough and has a high enough thrust to weight ratio it can keep on accelerating even in a steep climb. If the airspeed is increasing and the climb angle stays constant the angle of attack will actually decrease.

None the less I bet the factory pilots rehearse that manoeuvre and probably disabled MCAS.  They likely also had in mind the Airbus 320 Demo flight crash where the pilots where in inadvertently fighting HAL 9000.
https://www.youtube.com/watch?v=I9gELPxPG8Q (https://www.youtube.com/watch?v=I9gELPxPG8Q)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 17, 2019, 01:01:56 am
On the horizon i can see a large number of relatives preparing to sue Boing.
Quote
Boeing have been working on a software modification to MCAS since the Lion Air accident. Unfortunately although originally due for release in January it has still not been released due to both engineering challenges and differences of opinion among some federal and company safety experts over how extensive the changes should be. Apparently there have been discussions about potentially adding enhanced pilot training and possibly mandatory cockpit alerts to the package. There also has been consideration of more-sweeping design changes that would prevent faulty signals from a single sensor from touching off the automated stall-prevention system.

The FAA people involved in the process would have been unavailable from December 22 to January 25. Trump personally added a month to the schedule as part of the unintended consequences of his budget shutdown. Boeing can't release squat without FAA approval. Nor can they they resolve any engineering differences when the FAA isn't available. So Boeing should get a pass on at least a month of that delay.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 17, 2019, 04:48:04 pm
Somebody remind me why MCAS is even needed?
This 737 max 8 is presumably empty, but none the less, wow an impressive climb.

Actually, the MCAS was needed in part *because* of those powerful engines. They are more powerful and mounted farther forward than the engines on other 737s, so their power generates a higher turning moment that wants to push the nose up, so the danger of a stall is increased. Furthermore, once you the AOA very high, the nacelles themselves generate some lift (again, with a large moment because of the forward placement relative to the center of rotation), and that pushes for an even higher AOA. This is really only a problem once you are already at high AOA, but essentially the engines themselves become a destabilizing force once you get out of the safe zone.

MCAS is designed to keep the scenario from running away.

Pretty good explanation of why you don't add power immediately after a stall here: https://www.youtube.com/watch?v=TlinocVHpzk (https://www.youtube.com/watch?v=TlinocVHpzk)

Pretty good explanation of why high AOA's are more problematic in the MAX here: https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ (https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/)


Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 17, 2019, 05:57:23 pm
Hmmm, at what point does the Max become a different plane? When you start moving the engines around, changing its dynamics etc...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: mtdoc on March 17, 2019, 06:27:52 pm
Read this Twitter thread (https://twitter.com/trevorsumner/status/1106934362531155974?s=21) for an interesting take on the root causes.  Fuel prices/economic considerations led to a cascde of band aid design and sytems changes each one an attempt to compensate for problems introduced by the prior. The “software patch” is just the latest.

I won’t be surpised to see more of these kind of economics/complexity/systems problems in socierty going forward as there is more and more pressure on engineers to provide technology fixes to underlying economics/resource problems.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 17, 2019, 07:14:10 pm
Read this Twitter thread (https://twitter.com/trevorsumner/status/1106934362531155974?s=21) for an interesting take on the root causes.  Fuel prices/economic considerations led to a cascde of band aid design and sytems changes each one an attempt to compensate for problems introduced by the prior. The “software patch” is just the latest.

I won’t be surpised to see more of these kind of economics/complexity/systems problems in socierty going forward as there is more and more pressure on engineers to provide technology fixes to underlying economics/resource problems.

Providing technology fixes to economic problems is pretty much what engineering is. I think "An engineer can do for a dollar what any fool can do for two" is attributed to Arthur Wellington, a well known civil engineer from the late 1800's.

I don't really see the problem with Boeing setting the design goal for the MAX to improve performance without requiring a new type certificate. That the MCAS may be a bad implementation, or the specific engine placement requiring MCAS was a bad idea, or the whole thing has led to complex human+automation failure modes is a sign that maybe they screwed up.

But it is one thing to say that an engineering project failed, quite another to state as SO many have done, IMHO, talking without much knowledge, that the concept itself was doomed to fail. I suspect that in reality, Boeing will implement some fixes and there will be some training, and the MAX will ultimately become a safe airplane like the rest of the 737's.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Bud on March 17, 2019, 07:46:57 pm
It turns out i personally know someone who lost his family members on the Ethiopian flight.... Cant imagine what that person is going through...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 17, 2019, 07:58:44 pm
I suspect that in reality, Boeing will implement some fixes and there will be some training, and the MAX will ultimately become a safe airplane like the rest of the 737's.

Yes it will, I think so too, but with the MCAS... they royally screwed up.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 18, 2019, 02:44:19 am
Quote
Actually, the MCAS was needed in part *because* of those powerful engines. They are more powerful and mounted farther forward than the engines on other 737s, so their power generates a higher turning moment that wants to push the nose up, so the danger of a stall is increased. Furthermore, once you the AOA very high, the nacelles themselves generate some lift (again, with a large moment because of the forward placement relative to the center of rotation), and that pushes for an even higher AOA. This is really only a problem once you are already at high AOA, but essentially the engines themselves become a destabilizing force once you get out of the safe zone.

I'm struggling with this description. It makes it seem like the new engine placement has a tendency to push the nose of the plane up, and that is the main reason for MCAS.

From the pieces I have gathered, the problem requiring the MCAS is that the engine size and placement altered the aerodymanics of the plane in a way that made it unstable. It's not just a matter of the pilot needed to adjust the trim to adjust for a predictable and steady nose-up tendency. It sounds like the plane becomes unstable in a way that the trim would have to be whacked around up and down in rather large and fast adjustments to make the ride smoother.

In addition to this link posted by mtdoc, I have read another article that suggested the "ride comfort" was adversely affected the the change in engine position, and the MCAS was added to make the flight smoother. But, alas, I have no link.
Quote
Read this Twitter thread for an interesting take on the root causes. 

Trevor Sumner suggests that the software was never the problem and worked fine. That it was a bandaid that was necessary because of the change in engine placement and the resulting change in aerodynamics. But if anything, it sounds like the software bandaid was indeed part of what turned a "bumpy ride smoother-outer" into a death trap. Yes, the pilots should have cut out the stab trim or what not. And I don't know why there were never informed of the deadly potential problem with the MCAS. But it would have been very trivial (in hindsight) to make MCAS unable to override manual input to such a sustained degree. If it was there to make the ride smoother, then it could have been implemented (thru software) to be able to improve the ride without killing the passengers. Given that a sensor malfunction could have theoretically happened out of the blue at least as low as 6,000 feet and requiring manually turning off the system and course correction within just mere seconds (flipping multiple switches on the roof of the cabin while plummeting towards the earth in near free fall, then cranking the trim wheel bit by bit), it might have happened even with a prepared pilot that knew about the potential fault in advance.

In the light of what I'm inferring, the MCAS system would also have to account for resonant frequencies/oscillations, in addition to sensor malfunction. There would have to be some smarts to it, lets say. Not just a simple if/then cause and effect.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: TheSteve on March 18, 2019, 02:53:41 am
Are the new engines so powerful that MCAS is needed or is it purely a bandaid because the weight of the new engines changed the CG too much and they were too cheap to re-locate the wings to the proper place?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 18, 2019, 02:56:58 am
^that's what I am wondering.

AFAIK, the engines were too big for ground clearance. So to use the existing 737 frame, they had to change the mounting position.

Due to Boeing's philosophy that the plane should be able to fly with only manual control, I assume this means the new engines and mounting position are still safe and stable enough to be flown, manually... but I have inferred (right or wrong) that the ride would be less smooth/comfortable without MCAS.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: chickenHeadKnob on March 18, 2019, 03:06:02 am

I'm struggling with this description. It makes it seem like the new engine placement has a tendency to push the nose of the plane up, and that is the main reason for MCAS.


That is exactly the reason for MCAS ; safety, not ride comfort. Youtuber Mentour pilot, who is a 737NG captain explains this.

For powered aircraft there is a corner in the flight envelope at high angles of attack called "getting behind the power curve". Aerodynamically past a certain high angle of attack,  before full stall the sink rate/drag on the aircraft increases dramatically and if power is applied with low slung engines the pitch up moment makes things worse. 
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 18, 2019, 03:26:47 am
If that were the only reason for MCAS, why does it have to rely on a single AOA sensor, rather than the combination of sensors that create the stall warning / stick shake? If it only has to be in effect in near stall conditions, then it should not need to be active unless near a stall.

I'm also struggling with the plane going full throttle. Multiple sources suggest MCAS has control over the elevator with no mention of the throttle. 

There are multiple tidbits that suggest to me the MCAS was created to make the ride smoother, which requires a very fast and frequent input to perhaps the throttle in addition to the elevator. Boeing didn't want to offer the 737 MAX and have airliners complain that the ride is bumpier than the old planes?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: blueskull on March 18, 2019, 03:34:54 am
A stupid question here: why is MCAS needed in the first place? Isn't the pilot trained to push when the stick shaker is activated? There are some certain scenarios where the pilot must respond without referring the handbook, and they get well trained and well paid for executing those memory checklists well.

What's the problem trusting the pilot? Military planes don't have as much "safety" BS, and they don't fall from the sky for no reason.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 18, 2019, 03:39:10 am
^The US Airforce did experiments with reverse raked wings. This was inherently instable and required active electronic management of some of the control surfaces. This is kind of along the lines of what I am thinking that MCAS was actually made to do... to make faster than human adjustments to reduce the effects of inherent instability. Unlike the reverse wing fighter jets, which had complete runaway instability, perhaps the change in engines created some undesired oscillations between 2 or 3 points of shared stability which were not fatal (until incorrectly MCAS'd) but uncomfortable.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: chickenHeadKnob on March 18, 2019, 03:58:42 am
If that were the only reason for MCAS, why does it have to rely on a single AOA sensor, rather than the combination of sensors that create the stall warning / stick shake? If it only has to be in effect in near stall conditions, then it should not need to be active unless near a stall.


That the MCAS in default only use a single Angle of attack vane was a mistake by boeing. That stall warning is done with angle of attack sensors (and not "other" sensors) is because it is an aerodynamic phenomenon, not something to do with engines, a common misconception of non-pilots. From what I have read about MCAS, and the Mentourpilot video linked below, you are mistaken if you think MCAS is constantly trimming and flying the plane. It is constantly monitoring the angle of attack but only adding pitch down when it thinks the aircraft is approaching stall. It the recent crashes it looks like the system incorrectly initiated trim down when it didn't need to, and was fighting the pilots.

Have a look at Mentourpilot's video, he dumbs it down too much for my taste but it might help:
https://www.youtube.com/watch?v=TlinocVHpzk (https://www.youtube.com/watch?v=TlinocVHpzk)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 18, 2019, 04:09:39 am
Quote
Actually, the MCAS was needed in part *because* of those powerful engines. They are more powerful and mounted farther forward than the engines on other 737s, so their power generates a higher turning moment that wants to push the nose up, so the danger of a stall is increased. Furthermore, once you the AOA very high, the nacelles themselves generate some lift (again, with a large moment because of the forward placement relative to the center of rotation), and that pushes for an even higher AOA. This is really only a problem once you are already at high AOA, but essentially the engines themselves become a destabilizing force once you get out of the safe zone.

I'm struggling with this description. It makes it seem like the new engine placement has a tendency to push the nose of the plane up, and that is the main reason for MCAS.

Two separate phenomena that I intermingled. Adding power on a 737 when it is in/near a stall will generally make things worse. This is a generic problem with all airplanes with the engines below the wings, but it is certainly a bigger problem with more power at your disposal, and it is a bigger problem with the increased moment of the MAX engine position.

Furthermore, the reason MCAS was specifically designed for the MAX is that the *nacelles* themselves generate lift. (Almost any object in an airstream can generate lift if you hold it the right way.) They are designed to have neutral lift when in level flight, but as you turn the nose of the plane up, the engines actually want to push it up even more, and this is very pronounced at high angles of attack. I'm sure simulations showed that this instability is hard to recover from if not dealt with immediately, hence MCAS.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 18, 2019, 04:12:37 am
It's a Boeing design error and the S/W patch allowing "the option" of using two sensors stinks of cover-up. AOA DISAGREE alert indicator is also an "option"?!  :palm:

Using two sensors is still shitty because you have now doubled the probability of MCAS failure due to a sensor failure.
Multiple sensors iced up for the AF447 disaster. Would MCAS register a discrepancy with two sensors reading similar yet both are out to lunch?
I'll repeat the old adage "with two clocks you can never know the correct time". This MCAS system is never going to be stellar, even adding a third (sensor) opinion because the other pair can malfunction. It's just getting a slightly lower probability of failure, this is all Boeing can accomplish. Unless there was a gross S/W bug that is being fixed too.

In other industries with safety-critical design, you do fault-tree analysis and FMEDA to ensure you have coverage of a sensor problem, among other scenarios.
Clearly, Boeing bungled this and is showing a repeat bungle with their hasty "software fix" that cannot meet basic functional safety requirements even after piling on the algorithm smartness.
I've seen this before - a bad design safety-critical system is out there, sold in numbers and a corporation has a massive panic to fix it ASAP without changing any hardware.
Adding complex S/W algorithms (which can never be proven correct) is very dangerous.

Then I read this: (http://www.b737.org.uk/mcas.htm)
"MCAS is implemented within the two Flight Control Computers (FCCs). The Left FCC uses the Left AOA sensor for MCAS and the Right FCC uses the Right AOA sensor for MCAS. Only one FCC operates at a time to provide MCAS commands. With electrical power to the FCCs maintained, the unit that provides MCAS changes between flights. In this manner, the AOA sensor that is used for MCAS changes with each flight."

How do you come up with something so stupid?

The problem with "MCAS disagree" is that it does not necessarily mean there is a sensor problem. There are aerodynamic situations, such as a steep turn where correctly operating sensors can disagree. Hence, it is a reason to indicate something to the pilot, not a reason for the system to punt. I suspect, though, that the software patch will make it so MCAS will not activate on either sensor indicating high AOA, but only if both indicate high AOA. Well, that's just a guess.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 18, 2019, 04:34:39 am
Quote
That the MCAS in default only use a single Angle of attack vane was a mistake by boeing. That stall warning is done with angle of attack sensors (and not "other" sensors) is because it is an aerodynamic phenomenon, not something to do with engines, a common misconception of non-pilots.
Thanks but I understand that, already. In this case, other sensor could have told the MCAS system that the plane was not stalled. The fact that the plane is going 600 mph in the direction the nose is pointed should be a pretty good indicator of this. I don't know what all sensors that the plane has, but it seems like there are some other ways to detect a stall than the AOA. And the fact the stick shaker did not activate means that the malfunctioning AOA did not fool the stick shaker, right?

Quote
Furthermore, the reason MCAS was specifically designed for the MAX is that the *nacelles* themselves generate lift. (Almost any object in an airstream can generate lift if you hold it the right way.) They are designed to have neutral lift when in level flight, but as you turn the nose of the plane up, the engines actually want to push it up even more, and this is very pronounced at high angles of attack. I'm sure simulations showed that this instability is hard to recover from if not dealt with immediately, hence MCAS.
Thanks for this. I think you explained it in your previous post just fine, in hindsight, but I think I understand it better, now. It sounds like the MAX is inherently more prone to getting away from the pilot and stalling at high AOA maneuvers, and it harder to recover from, requiring much greater input to the elevator and less ability to add useful thrust? Essentially, without electronic help, the MAX has less maneuverability. And any electronic aid should only ever need to be fleeting, to bring the plane back from the "runaway" edge of maneuverability. Jacking the elevator full down for 30 seconds seems like a scenario that would be helpful... never? If a pilot is pushing a passenger jet carrying 200 people to the utmost limit, you'd think he has a really, really good and really, really imminent reason... like to avoid hitting something (including the ground).

I am curious why the plane was on full throttle. Do any pilots have a theory here? The plane was supposedly going 600mph and on full thrust. Maybe this is a normal pilot response.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 18, 2019, 07:16:33 am
A stupid question here: why is MCAS needed in the first place? Isn't the pilot trained to push when the stick shaker is activated? There are some certain scenarios where the pilot must respond without referring the handbook, and they get well trained and well paid for executing those memory checklists well.

What's the problem trusting the pilot? Military planes don't have as much "safety" BS, and they don't fall from the sky for no reason.

Actually they do, quite regularly, not counting combat losses:
https://en.wikipedia.org/wiki/List_of_accidents_and_incidents_involving_military_aircraft_(2010%E2%80%93present) (https://en.wikipedia.org/wiki/List_of_accidents_and_incidents_involving_military_aircraft_(2010%E2%80%93present))

The difference is in the number of casualties and who investigates. In fixed wing combat aircraft, generally all seats are ejection seats, so survival rates are high. In transport aircraft and helicopters, there are still far fewer people involved in most cases.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 18, 2019, 07:24:27 am
I am curious why the plane was on full throttle. Do any pilots have a theory here? The plane was supposedly going 600mph and on full thrust. Maybe this is a normal pilot response.
Well if you know that engine thrust on the aircraft tends to push the nose up, and one is desperately trying to get the nose up, it makes some sense to pour on the throttle to get the nose up.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 18, 2019, 09:20:08 am
And another question: if there is a huge structural error in this plane, why did "only" two planes crash in half a year time ?
Are there more incidents, reports from pilots that just in time got the plane under control by disabling the computer and take manual control? Haven't heard about them ?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 18, 2019, 09:39:40 am
And another question: if there is a huge structural error in this plane, why did "only" two planes crash in half a year time ?
Are there more incidents, reports from pilots that just in time got the plane under control by disabling the computer and take manual control? Haven't heard about them ?

Yes, there are reports of at least two other pilots that have had to deactivate MCAS during takeoff.

Edit: Not the MCAS, had to disable the autopilot it seems:
http://time.com/5550449/pilots-boeing-737-max-issues/ (http://time.com/5550449/pilots-boeing-737-max-issues/)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Daixiwen on March 18, 2019, 09:46:31 am
And another question: if there is a huge structural error in this plane, why did "only" two planes crash in half a year time ?
From what we know so far the MCAS becomes a problem if the angle of attack sensor gives a false reading. I sure hope the sensor is not *that* bad.

A sensor meeting the "major failure" safety requirement must have a failure rate less than 1/100000. Are there any statistics of how many total 737 MAX flights have occurred since its launch?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 18, 2019, 09:53:39 am
Yes, there are reports of at least two other pilots that have had to deactivate MCAS during takeoff.
Ok 5 incidents in a half year for 350 planes flying at least two flights a day , so 5 incidents over 127000+ flights.

EDIT: the plane has been in service since 2016 so that would be miliions of flights and only now it occurs.

Don't get me wrong it is good to get to the bottom of this, but it looks like it will be pretty hard to exactly determine the cause if it only happens under certain very specific conditions.
Good that the flightrecorders are there, otherwise it would be a needle in a haystack.

Quote
There are approximately 350 Boeing 737 Max 8 aircraft in operation worldwide, being flown by 54 operators, according to the US Federal Aviation Administration (FAA).5 days ago
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 18, 2019, 10:36:45 am
Quote
it looks like it will be pretty hard to exactly determine the cause...
Or... maybe not.

https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ (https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/)

Apologies if someone else has already linked this. It seems like it was published within the last 18 hours. It seems pretty clear, so far. It contains almost all the important details in this thread but without the faff.

1. FFA let Boeing approve its own plane, in some ways.
2. The MCAS was said to move the elevator only 0.6 degrees. But Boeing increased it to 2.5 degrees after test flights. No one told this to the FAA.
3.  After the elevator is manually moved by the pilot, the MCAS can re-trigger. Doing a full 2.5 degrees again. (In the Ethiopian Airlines flight, the captain corrected the plane 21 times, then he handed the plane to the FO. The FO made only a tiny, partial correction after MCAS triggered. Then it triggered again. This put the elevator to full nose down, and the plane crashed shortly after.)
4. Boeing didn't include info about MCAS to its customers, at all.
5. MCAS was probably incorrectly classified. FFA approved the original classification based on 0.6 degrees of elevator adjustment. That changed to 2.5 (and was actually unlimited, due to retriggering). And even they way it was initially classified, it still needed to have two sensors, not just one.
6. They didn't consider the human factor of what happens to a pilot when 2.5 degrees of elevator adjustment is made out of the blue and repeatedly retriggers and no one told them this could even happen. 5 degrees is basically maximum nose dive; so I think "panic" might be on the menu. I wonder how many 737 commercial (not test) pilots have ever intentionally used even 2.5 degree downward angle on a flight.

So basically, this MCAS system, in the hands of a pilot who has spent 6,000 hours of flight time living by very small and gradual adjustments and essentially "not messing up", becomes a shoddy encoder wheel, where you manage to turn the volume up by 1, then it goes down by 10, then up by 1, then down by another 10. And then the music stops playing.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 18, 2019, 11:08:30 am
Yes, there are reports of at least two other pilots that have had to deactivate MCAS during takeoff.
Ok 5 incidents in a half year for 350 planes flying at least two flights a day , so 5 incidents over 127000+ flights.

EDIT: the plane has been in service since 2016 so that would be miliions of flights and only now it occurs.

Don't get me wrong it is good to get to the bottom of this, but it looks like it will be pretty hard to exactly determine the cause if it only happens under certain very specific conditions.
Good that the flightrecorders are there, otherwise it would be a needle in a haystack.

Quote
There are approximately 350 Boeing 737 Max 8 aircraft in operation worldwide, being flown by 54 operators, according to the US Federal Aviation Administration (FAA).5 days ago

The first 737 MAX commercial flight was in May, 2017. Wherever you got 2016 from was probably publicity about the aircraft making test flights.

You might find these easy-to-find numbers more useful: https://en.wikipedia.org/wiki/List_of_Boeing_737_MAX_orders_and_deliveries (https://en.wikipedia.org/wiki/List_of_Boeing_737_MAX_orders_and_deliveries)

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: chickenHeadKnob on March 18, 2019, 11:11:03 am
Thanks but I understand that, already. In this case, other sensor could have told the MCAS system that the plane was not stalled. The fact that the plane is going 600 mph in the direction the nose is pointed should be a pretty good indicator of this. I don't know what all sensors that the plane has, but it seems like there are some other ways to detect a stall than the AOA. And the fact the stick shaker did not activate means that the malfunctioning AOA did not fool the stick shaker, right?


Other sensors might inform the MCAS software that the the aircraft is in a "this can't happen" situation but then what. I suspect the flight law software would choose to believe the angle of attack indicator over  conflicting information as they should be more reliable than the rest. For what it is worth the stall horn  in piston aircraft is  a very simple reliable device, it roughly forms the same function. As the angle of attack approaches stall the vane rotates and a noise is made, then the pilot needs to take action and lower the nose.

The problem in 737Max case is that MCAS kicks in and starts quietly adding downward trim before the stick shaker angle of attack. And as far as I know this only this happens in manual flight mode. This was poorly explained to the pilots who's first reaction would be to countermand that input with opposite trim with the trim hat on the yoke. That apparently is not the way you disable MCAS and it keeps on fighting your inputs.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BradC on March 18, 2019, 11:15:37 am
3.  After the elevator is manually moved by the pilot, the MCAS can re-trigger. Doing a full 2.5 degrees again. (In the Ethiopian Airlines flight, the captain corrected the plane 21 times, then he handed the plane to the FO.

Fuck me drunk. I'm sorry. What ?? 21 times??
"Here, the thing is fucked and we're all going to die. You deal with it".
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 18, 2019, 11:28:56 am
3.  After the elevator is manually moved by the pilot, the MCAS can re-trigger. Doing a full 2.5 degrees again. (In the Ethiopian Airlines flight, the captain corrected the plane 21 times, then he handed the plane to the FO.

Fuck me drunk. I'm sorry. What ?? 21 times??
"Here, the thing is fucked and we're all going to die. You deal with it".

Wrong take on it. It was more likely something along the lines of, "My controls aren't working right, try yours!" Which is a perfectly reasonable thing to try. Redundancy on all the primary flight controls and instruments from side to side is deliberate, just in case one side breaks in some way.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Towger on March 18, 2019, 11:31:13 am
Are the new engines so powerful that MCAS is needed or is it purely a bandaid because the weight of the new engines changed the CG too much

It can take off like a Vulcan bomber:

https://youtu.be/RyeqeqSNSgQ
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BradC on March 18, 2019, 11:37:56 am
Wrong take on it. It was more likely something along the lines of, "My controls aren't working right, try yours!" Which is a perfectly reasonable thing to try. Redundancy on all the primary flight controls and instruments from side to side is deliberate, just in case one side breaks in some way.

Yep. Not a pilot and done nothing more than a couple of (really fun) lessons in a Cessna, so happy to take that. Still, the difference between the Captain trying 21 times and the first officer pushing it into the dirt is peculiar.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 18, 2019, 11:58:32 am
Quote
It can take off like a Vulcan bomber:
Wowzers. The video says the plane experiences zero gravity when it leveled off. If you could get all the passengers to sign a waiver, I'd be the first one to.... watch the cell phone videos.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: chickenHeadKnob on March 18, 2019, 12:10:40 pm
Quote
It can take off like a Vulcan bomber:
Wowzers. The video says the plane experiences zero gravity when it leveled off. If you could get all the passengers to sign a waiver, I'd be the first one to.... watch the cell phone videos.

Getting to negative G is trivial to do in any aircraft, even a glider. It doesn't have anything to do with the climb rate.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 18, 2019, 12:11:51 pm
Standard airshow stuff for new planes. Light fuel load and a completely empty cabin. Even the passenger seats and cabin trim may be missing. Much bigger power to weight ratio than a normal commercial takeoff.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 18, 2019, 12:35:15 pm
It can take off like a Vulcan bomber:

Now that really was something to experience! I remember an airshow at RAF Finningley when I was a kid, back when they were still fully operational. One gently cruised in at low level and then, half way along the runway, just sat on its tail and went up almost vertically. The feeling of my chest being forcibly compressed completely overwhelmed the indescribable roar.

It left a lasting impression even after all these years, I've never experienced anything like it again. That level of noise exposure would never be allowed these days of course.

Sorry, OT.

P.S. I saw its last airshow at Yeovilton. Sadly, they were very gentle on the airframe and engines, they did deploy the parachute though.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: nfmax on March 18, 2019, 01:30:49 pm
Standard airshow stuff for new planes. Light fuel load and a completely empty cabin. Even the passenger seats and cabin trim may be missing. Much bigger power to weight ratio than a normal commercial takeoff.
A long time ago, I flew in a British Midland 747 from San Diego to LHR. The aircraft had flown from LHR to LAX, then the little hop down to San Diego to drop off the last few passengers. It took off with about 30 passengers on board, and hardly any fuel. Whoosh....
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: LapTop006 on March 18, 2019, 02:34:47 pm
Standard airshow stuff for new planes. Light fuel load and a completely empty cabin. Even the passenger seats and cabin trim may be missing. Much bigger power to weight ratio than a normal commercial takeoff.
A long time ago, I flew in a British Midland 747 from San Diego to LHR. The aircraft had flown from LHR to LAX, then the little hop down to San Diego to drop off the last few passengers. It took off with about 30 passengers on board, and hardly any fuel. Whoosh....

Qantas used to fly LAX->AKL->MEL, one day by chance I happened to hop on the AKL->MEL leg, after the vast majority of passengers & cargo had left, along with the light fuel load for such a short hop it took off like the proverbial bat out of hell.

One of my favourite flying memories.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 18, 2019, 02:48:38 pm
^The US Airforce did experiments with reverse raked wings. This was inherently instable and required active electronic management of some of the control surfaces. This is kind of along the lines of what I am thinking that MCAS was actually made to do... to make faster than human adjustments to reduce the effects of inherent instability. Unlike the reverse wing fighter jets, which had complete runaway instability, perhaps the change in engines created some undesired oscillations between 2 or 3 points of shared stability which were not fatal (until incorrectly MCAS'd) but uncomfortable.
Seams both US X29 and Sovjets SU47 got raked wing concept from Junkers Ju287 which all of them suffered from warping wings at certain flight conditions which a MCAS would not fix i presume.
https://www.youtube.com/watch?v=mOCUTyoi9eo (https://www.youtube.com/watch?v=mOCUTyoi9eo)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: boffin on March 18, 2019, 03:22:28 pm
But, because these sticks are not coupled and do not have any force feedback, the pilots did not know what the other one was doing.

This is something that has always struck me as an absolutely stupid design. If the plane has two sticks, they should absolutely be mechanically linked together, or only one set of controls should be active at a time, with a very obvious indication of which is active. I never liked the sidestick arrangement anyway, it just looks wrong, and seems like it would be awkward.

Actually in most modern passenger aircraft the left controls are connected to the left elevator, the right controls, right elevator and there's a sheer pin that can be broken (on purpose) if there's a jam, so that each side independently controls elevators; everything from roughly Dash-8 and bigger.  Egypt Air 990 was a case where this was highlighted in what appears to be pilot v pilot fight for  the aircraft.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 18, 2019, 04:26:48 pm
Standard airshow stuff for new planes. Light fuel load and a completely empty cabin. Even the passenger seats and cabin trim may be missing. Much bigger power to weight ratio than a normal commercial takeoff.
A long time ago, I flew in a British Midland 747 from San Diego to LHR. The aircraft had flown from LHR to LAX, then the little hop down to San Diego to drop off the last few passengers. It took off with about 30 passengers on board, and hardly any fuel. Whoosh....

I used to do a fairly regular trip to Cork airport from LHR. Cork is a small airport built on the top of a hill (you can't see one end of the runway from the other, subject to low cloud too). On days with unfavourable wind direction and speed (frequent) taking of from Cork used to involve bringing the tanker out, taking fuel off the plane (737) and using the short cross runway... Taxi right to the very end, turn without going onto the grass, full brakes, full throttle and release. As you say, "Whoosh...."

The plane would then fly to Shannon (much bigger, international flights), to fill up with sufficient fuel to fly back to LHR. I kid you not!

This was back in the '80s https://en.wikipedia.org/wiki/Cork_Airport (https://en.wikipedia.org/wiki/Cork_Airport)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 18, 2019, 04:47:41 pm
It sounds like the MAX is inherently more prone to getting away from the pilot and stalling at high AOA maneuvers, and it harder to recover from, requiring much greater input to the elevator and less ability to add useful thrust?

Yes, I think this is basically true, but the caveat is that it gets unstable once you've already gotten it into a high AOA situation, which in normal ops should not happen. You might say that a pilot's #1 one job flying and airplane is keeping the wing flying, so this defect -- that the plane is a problematic performer at high AOA -- is perhaps less of an operational defect than it seems.

Essentially, without electronic help, the MAX has less maneuverability.

Again, this is not an airshow stuntplane, it's maneuverability at high AOA isn't generally that important, because it's not supposed to be there. And indications so far from these accidents is that the plan did not have high AOA when the problem kicked in. A faulty sensor made it *think* it was experiencing high AOA.


If a pilot is pushing a passenger jet carrying 200 people to the utmost limit, you'd think he has a really, really good and really, really imminent reason... like to avoid hitting something (including the ground).

History has shown it both ways. Sometimes a pilot correctly pushes a plane beyond its safe envelope because of good reason that requires it, sometimes pilots have caused accidents by doing so.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 18, 2019, 04:50:10 pm
The problem in 737Max case is that MCAS kicks in and starts quietly adding downward trim before the stick shaker angle of attack. And as far as I know this only this happens in manual flight mode. This was poorly explained to the pilots who's first reaction would be to countermand that input with opposite trim with the trim hat on the yoke. That apparently is not the way you disable MCAS and it keeps on fighting your inputs.

I'm not quite certain of this, but I believe in the Lionair case, the published data show that the stick shaker was going on one side. I haven't seen the ET data yet. I'd be surprised if MCAS before the stick shaker kicks in, but there's a lot surprising in these accidents.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: G7PSK on March 18, 2019, 05:47:52 pm
It can take off like a Vulcan bomber:

Now that really was something to experience! I remember an airshow at RAF Finningley when I was a kid, back when they were still fully operational. One gently cruised in at low level and then, half way along the runway, just sat on its tail and went up almost vertically. The feeling of my chest being forcibly compressed completely overwhelmed the indescribable roar.

It left a lasting impression even after all these years, I've never experienced anything like it again. That level of noise exposure would never be allowed these days of course.

Sorry, OT.

P.S. I saw its last airshow at Yeovilton. Sadly, they were very gentle on the airframe and engines, they did deploy the parachute though.
I used to have workshop 400 meters from the main runway at RAF Marha,Marham Norfolk, all the air shows by the Vulcan bomber as the ground control officer was based there so I used to see the vulcan doing it's thing several times a year over about a 15 year period. Also saw and heard the Victor tankers taking off at all times of the day and night as with the Canberra's reconosance and the Tornado's, The noise level was so graet at times that it caused mortar to run down the walls, the engine run up area was less than 50 meters from my workshop. The only good side was the neighbors did complain about any noise I made at any time of day or night in the workshop.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 18, 2019, 08:05:51 pm
It's terrible to see engineers forced to either roll out unsafe shit, or lose their job.

The managers, executives etc. suffer little for their corruption, even when caught. One or two people might get fined or some jail time, despite hundreds killed.

Further proof is the way Boeing is handling things, as a "software upgrade" which doesn't even cover the AOA sensors having poor reliability in the first place.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 18, 2019, 08:11:57 pm
Further proof is the way Boeing is handling things, as a "software upgrade" which doesn't even cover the AOA sensors having poor reliability in the first place.

Wait, wait... perhaps it's not the sensors' fault, but a software bug.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Gyro on March 18, 2019, 08:30:55 pm
A storm is slowly but surely approaching Boeing, (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump))

...

Every time politicians, MBAs and managers meddle with technical issues something fails.

"... participated in phone conversations with top Boeing executives and other stakeholders, offering his thoughts on the aviation industry. But since then, he has faced criticism that his over-involvement stymied the FAA from acting sooner. "

Nooooooh!   :palm:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 18, 2019, 08:49:44 pm
Further proof is the way Boeing is handling things, as a "software upgrade" which doesn't even cover the AOA sensors having poor reliability in the first place.

Wait, wait... perhaps it's not the sensors' fault, but a software bug.

The AOA sensor is first in the chain of events, it triggers the MCAS software. Unless the flight control software has huge bugs...

MCAS I thought only activates in manual mode, and the prior complaints by two pilots had problems when autopilot was engaged, when MCAS should be disabled then.
Also, autothrottle did not work in one instance. This implies there's some other problem.

https://www.washingtonpost.com/business/economy/sensor-cited-as-potential-factor-in-boeing-crashes-draws-scrutiny/2019/03/17/5ecf0b0e-4682-11e9-aaf8-4512a6fe3439_story.html?noredirect=on&utm_term=.271f3763b148 (https://www.washingtonpost.com/business/economy/sensor-cited-as-potential-factor-in-boeing-crashes-draws-scrutiny/2019/03/17/5ecf0b0e-4682-11e9-aaf8-4512a6fe3439_story.html?noredirect=on&utm_term=.271f3763b148)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 19, 2019, 02:01:09 am
Even if there's no software bug, even if the AOA sensor is the most reliable sensor on the plane, there is an error in the design/implementation. If software bugs are also discovered, oh boy. Not that the engineers are the fault. Mistakes happen, and that is why the approval process (normally) takes as long as it does.

Quote
A storm is slowly but surely approaching Boeing, (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump))
Sure, Boeing is going to be "Shenzu Air" after Chinese investors buy it. J/K. They'll get a government bailout, if it comes to that. Maybe one scapegoat goes to jail for 2 years. But what about the FAA? Surely a bunch of those guys can be liberated from the federal payroll and offered some time behind bars for endangerment of human life if not bribery. And who knows how high up this goes into the government? Does it even end at the FAA?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 19, 2019, 02:14:56 am
Even if there's no software bug, even if the AOA sensor is the most reliable sensor on the plane, there is an error in the design/implementation. If software bugs are also discovered, oh boy. Not that the engineers are the fault. Mistakes happen, and that is why the approval process (normally) takes as long as it does.

Quote
A storm is slowly but surely approaching Boeing, (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump))
Sure, Boeing is going to be "Shenzu Air" after Chinese investors buy it. J/K. They'll get a government bailout, if it comes to that. Maybe one scapegoat goes to jail for 2 years. But what about the FAA? Surely a bunch of those guys can be liberated from the federal payroll and offered some time behind bars for endangerment of human life if not bribery. And who knows how high up this goes into the government? Does it even end at the FAA?

You guys seem awfully sure that Boeing and the FAA worked together to sell an airplane they knew was unsafe. I'll agree, I think that if that is proven, the punishment should be very severe. But I think you do not need that kind of behavior to produce a bad outcome. I think it's interesting that so many people do. What incentive do either of those organizations have to certify a passenger killing machine?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: imo on March 19, 2019, 12:29:51 pm
Quote
Airlines want safety, but with margins so slim, they are forced to worry about their bottom line. And the FAA wants safety, but needs to weigh the Cost-Benefit of each new advance. So in the end, it is often Tombstone Technology and accidents -- that drive the industry forward.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on March 19, 2019, 02:10:15 pm
Can there be a 737 Max pilot that does not know about MCAS and how to respond when it acts up anywhere in the world at this point?

Did Boeing actually send out mandatory to read information to airlines explaining the MCAS system after the first accident? Or would those pilots have to have followed the news, with all its inaccuracies?

If Boeing continued to pretend that pilots really didn't need to know there was an automatic control in a plane where pilots very much expect there not to be one, that's still on them.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: mtdoc on March 19, 2019, 03:00:50 pm
Uh hu..

The 737 MAX Saga Is a Total Disgrace for Boeing and the FAA (https://libertyblitzkrieg.com/2019/03/18/the-737-max-saga-is-a-total-disgrace-for-both-boeing-and-the-faa/)

Quote
This whole affair seems like a perfect microcosm for our twisted and broken modern U.S. economy and culture in general. Greed, regulatory capture and death — it has it all.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 19, 2019, 03:07:55 pm
Even if there's no software bug, even if the AOA sensor is the most reliable sensor on the plane, there is an error in the design/implementation. If software bugs are also discovered, oh boy. Not that the engineers are the fault. Mistakes happen, and that is why the approval process (normally) takes as long as it does.

Quote
A storm is slowly but surely approaching Boeing, (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump (https://www.theverge.com/2019/3/18/18270910/boeing-faa-investigation-max-8-mcas-trump))
Sure, Boeing is going to be "Shenzu Air" after Chinese investors buy it. J/K. They'll get a government bailout, if it comes to that. Maybe one scapegoat goes to jail for 2 years. But what about the FAA? Surely a bunch of those guys can be liberated from the federal payroll and offered some time behind bars for endangerment of human life if not bribery. And who knows how high up this goes into the government? Does it even end at the FAA?
Mmkaay, now FBI with special counsel Miiuulleeerr and DOJ is setting up a investigation to Russian collusion as they suspect Piutin has caused the MCAS software bug. 2 years later no collusion was found and Miiuulleer refuses to release clown report while Dumpf having tea and cakes with Boing CEO..
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 19, 2019, 03:36:54 pm
Perhaps already posted, just in case:

https://www.eetimes.com/author.asp?section_id=36&doc_id=1334444 (https://www.eetimes.com/author.asp?section_id=36&doc_id=1334444)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on March 19, 2019, 04:43:03 pm
The Hudson river landing was a good example of why pilots need an internalized model of the flight system and why arcane rote procedures to deal with failures are not enough.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SeanB on March 19, 2019, 04:53:14 pm
I used to have workshop 400 meters from the main runway at RAF Marha,Marham Norfolk, all the air shows by the Vulcan bomber as the ground control officer was based there so I used to see the vulcan doing it's thing several times a year over about a 15 year period. Also saw and heard the Victor tankers taking off at all times of the day and night as with the Canberra's reconosance and the Tornado's, The noise level was so graet at times that it caused mortar to run down the walls, the engine run up area was less than 50 meters from my workshop. The only good side was the neighbors did complain about any noise I made at any time of day or night in the workshop.

OHS came around one day where I was, to measure sound levels. Coincidentally there was an Atar 09k50 in the test bed being given an after service check. Started, run till warm then the full power with full afterburner test while they were measuring sound pressure levels in the complex. 130dB plus, a half kilometer away from the test bed, and nobody noticed it as it was normal.

Now scary was when I accidentally got a flight in an aircraft that officially did not exist, and we needed all 4km of runway, plus a little more, to take off. Was a very interesting flight, but again, no cameras were allowed.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 19, 2019, 05:21:45 pm
The Hudson river landing was a good example of why pilots need an internalized model of the flight system and why arcane rote procedures to deal with failures are not enough.

This, I think is the first good argument I've heard for why 737 pilots need to know about MCAS.

As it happens, during the USAir 1549 landing, the A320's control systems did not let Sullenberger flare the way he had wanted to. The outcome was fine, but if the system had been more aggressive in "protecting the envelope" maybe it would not have been. At least he knew what the system would do.

https://www.youtube.com/watch?v=cKuw49KBywA (https://www.youtube.com/watch?v=cKuw49KBywA)

But the thing is that flight manuals do not provide internalized models of how an airplane really flies. You have to get that from operating the machine. And furthermore, if you operate it carefully, within normal parameters associated with passenger flight, you won't get exposed to the extreme flight regimes where this knowledge is actually useful and important. So you can have 10,000 hours in a plane and still not know what it will do in an unusual situation. This *is* something you can learn in a simulator, if it is sufficiently faithful, and I think that is one learning that I think experts can already agree on regarding the MAX: the pilots should have gotten more sim time, including time that exposes them to the behavior of the aircraft in unusual scenarios that are specific to that model.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 19, 2019, 06:26:22 pm
But, because these sticks are not coupled and do not have any force feedback, the pilots did not know what the other one was doing.

This is something that has always struck me as an absolutely stupid design. If the plane has two sticks, they should absolutely be mechanically linked together, or only one set of controls should be active at a time, with a very obvious indication of which is active. I never liked the sidestick arrangement anyway, it just looks wrong, and seems like it would be awkward.

Actually in most modern passenger aircraft the left controls are connected to the left elevator, the right controls, right elevator and there's a sheer pin that can be broken (on purpose) if there's a jam, so that each side independently controls elevators; everything from roughly Dash-8 and bigger.  Egypt Air 990 was a case where this was highlighted in what appears to be pilot v pilot fight for  the aircraft.


You're not likely to break that shear pin without knowing it though. On the Airbus planes the two sticks are not mechanically linked in any way at all, if one pilot is pulling back or pushing forward hard on their stick you wouldn't know by holding yours.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 19, 2019, 07:17:07 pm
Quote
Mmkaay, now FBI with special counsel Miiuulleeerr and DOJ is setting up a investigation to Russian collusion as they suspect Piutin has caused the MCAS software bug. 2 years later no collusion was found and Miiuulleer refuses to release clown report while Dumpf having tea and cakes with Boing CEO..

I like my tinfoil hats, so fair enough. But wait and see. FAA was fasttracking these approvals because someone was poking/pressuring them and or there was some major personal interest or incentive. Maybe Boeing hires retired FAA officials as consultants, and that is enough. Maybe there's more inbreeding and impropriety than that, even. I imagine Boeing is a very important company to our country's military and government.* And somehow many people were actively not doing their jobs and looking the other way.

*Transportation Secretary Elaine Chao even rode in a 737 MAX two days after the latest crash.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 19, 2019, 07:38:11 pm
But the thing is that flight manuals do not provide internalized models of how an airplane really flies. You have to get that from operating the machine. And furthermore, if you operate it carefully, within normal parameters associated with passenger flight, you won't get exposed to the extreme flight regimes where this knowledge is actually useful and important. So you can have 10,000 hours in a plane and still not know what it will do in an unusual situation. This *is* something you can learn in a simulator, if it is sufficiently faithful, and I think that is one learning that I think experts can already agree on regarding the MAX: the pilots should have gotten more sim time, including time that exposes them to the behavior of the aircraft in unusual scenarios that are specific to that model.
That is the whole point is it not? According to that eetimes article Boeing claimed that any experienced 737 pilot did not need additional training or simtime for the max.
That is also why it was a big seller, the airlines did not have to invest in hours of training and that was a massive saving. It is also probably in the future the reason that if there has to be substantial additional training, the airlines will cancel their orders.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 19, 2019, 07:52:32 pm
Quote
But the thing is that flight manuals do not provide internalized models of how an airplane really flies. You have to get that from operating the machine. And furthermore, if you operate it carefully, within normal parameters associated with passenger flight, you won't get exposed to the extreme flight regimes where this knowledge is actually useful and important. So you can have 10,000 hours in a plane and still not know what it will do in an unusual situation. This *is* something you can learn in a simulator, if it is sufficiently faithful, and I think that is one learning that I think experts can already agree on regarding the MAX: the pilots should have gotten more sim time, including time that exposes them to the behavior of the aircraft in unusual scenarios that are specific to that model.
In this case, experiencing/simulating what the plane does in an extreme handling situation is not enough. They should need to experience what it is like not only when MCAS kicks in during the edge of stall. The training should also include the MCAS kicking in "out of the blue" during routine flight. This is a completely different experience with potentially very little time to react. If the plane pulls more than 1 negative G during this malfunction, it is going to be hard to even simulate. Reading a manual and sim might not even be enough, because of "instinctual" or automatic human response. Simulation is good, but now do it when you're cruising along with everything normal when the floor drops out from under you, you are disoriented, and the first and foremost thing being pressed onto your adrenaline soaked pea brain as you regain your orientation is the ground ending your life within the next 25 seconds unless you fix the problem within the first few of those seconds. And all the while you hear the screams of 200 passengers who are sure they're about to die through the cabin wall.

Military helicopter pilots are trained to evacuate the vehicle in a water crash, and the only effective simulation involves a giant tank of water and a fake helicopter that spins and dunks them upside down in the water. Apparently, only a small percentage of trainees make it out on the first try, even though they know exactly what is coming and when. This training greatly increased the survival rate of pilots in water landings. Simply knowing what to do and practicing under normal conditions did not help.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 19, 2019, 09:06:38 pm
But the thing is that flight manuals do not provide internalized models of how an airplane really flies. You have to get that from operating the machine. And furthermore, if you operate it carefully, within normal parameters associated with passenger flight, you won't get exposed to the extreme flight regimes where this knowledge is actually useful and important. So you can have 10,000 hours in a plane and still not know what it will do in an unusual situation. This *is* something you can learn in a simulator, if it is sufficiently faithful, and I think that is one learning that I think experts can already agree on regarding the MAX: the pilots should have gotten more sim time, including time that exposes them to the behavior of the aircraft in unusual scenarios that are specific to that model.
That is the whole point is it not? According to that eetimes article Boeing claimed that any experienced 737 pilot did not need additional training or simtime for the max.
That is also why it was a big seller, the airlines did not have to invest in hours of training and that was a massive saving. It is also probably in the future the reason that if there has to be substantial additional training, the airlines will cancel their orders.

Yes, that was the aircraft's goal and claim. And pilots are really trained these days to avoid the need for heroic mastery of ship's aerodynamics rather than trying to achieve such mastery. Today's pilots just don't have great stick and rudder skills, and that's turned out to be safe for the most part because other than trying to fly actually broken or malfunctioning aircraft, such skills rarely come up. They do, from time to time: USAir 1549, good outcome, AF447, bad outcome.

MCAS was designed to keep pilots from ever experiencing the instability of a MAX at extreme AOA. This was probably judged safer than trying to teach pilots to deal with it. Folks are saying that was not a sound engineering decision and I think they don't generally know what they're talking about. These are complex decisions, and history and human factors, and what can be expected of 1 std dev below mean pilots all figure into it.

But MCAS introduced a new failure mode (or modes) of its own, due to mistakes or poor enginneering, or reasons still unknown, and pilots have obviously not been able to handle that. The solution could be training on these failure modes or it could be fixing MCAS, or all of the above.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 19, 2019, 11:22:16 pm
It seems to me they're going to end up needing additional training no matter what. Especially if these two accidents turn out to be caused by MCAS malfunctions, the pilots absolutely need to know what to do in the event that system fails and how to override it.

As far as stick & rudder skills, IMHO knowing how to deal with failures and fly by hand when necessary is exactly the reason we have professional pilots in the cockpit rather than an operator just skilled enough to monitor the automated systems. I worry that too much automation, not just in planes but now in cars too becomes a crutch, enabling people to become complacent and dependent on the technology and unable to step in when the technology inevitably fails in certain edge cases.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tautech on March 19, 2019, 11:52:33 pm
Here in NZ pilot skills are assessed as in you're critiqued constantly by one another and have a few trips to the sim each year where assessment jumps to another level.
In the sim you're thrown all sorts of swerve balls and emergency situations that in particular the Captain must master.
Trouble is, if a particular situation is not able to be simulated pilots must refer to their basic flying skills in order to sort it out but if the plane is fighting them thinking it knows better, well Houston, we have a problem.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 20, 2019, 12:39:01 am
MCAS was designed to keep pilots from ever experiencing the instability of a MAX at extreme AOA.

It was introduced for a reason (https://en.wikipedia.org/wiki/Boeing_737_MAX#Maneuvering_Characteristics_Augmentation_System_(MCAS)) - due to forward & up engine placement of MAX (compared to older models) which cause an upward pitching moment that leads to increased AOA and risk of stall. Some facts regarding Flight 302 are interesting: plane crashed with MCAS in "full nosedive mode", yet during last moments of flight plane gained altitude and speed according to flightradar24 data (https://graphics.reuters.com/ETHIOPIA-AIRPLANE/0100911Q1DX/index.html). Pilots have option to disengage automatic stabilizer trim and crank it mechanically using wheel, but seems that instead of taking control over MCAS, they simply fought it - continued to climb at full(?) throttle, reached high speeds with stabilizer in nosedive position and lost control over plane. [all this just speculation of armchair investigator]
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on March 20, 2019, 01:58:28 am
Pilots have option to disengage automatic stabilizer trim

An option they didn't think was relevant with the autopilot turned off.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 02:39:50 am
Pilots have option to disengage automatic stabilizer trim

An option they didn't think was relevant with the autopilot turned off.

I don't think that's true. The trim wheels are moving by themselves. They are large and very obvious when turning. They also make a loud clacking. That is it dead obvious that the machine is retrimming the stab. You might not know why it is happening, but you know that it is. And the procedure to make it stop no matter the reason is simple. You don't need to know what subsystem is commanding the stab trim to disable it.

If the pilots wanted to disconnect the trim motors, they could have easily. That they didn't is a mystery that the CVRs will hopefully reveal. But I suspect the reason was that they weren't completely sure the machine didn't have a good reason to do what it was doing. They're trained to avoid stalls, and if the machine is saying down, down, down, you have to be really confident you know better to disconnect it entirely.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on March 20, 2019, 03:39:32 am
If the pilots wanted to disconnect the trim motors

That's a different switch though, the autopilot trim switch was in their mind irrelevant.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: mtdoc on March 20, 2019, 05:48:19 am
Prediction:  The 737 Max will not fly again.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: blueskull on March 20, 2019, 05:57:57 am
Prediction:  The 737 Max will not fly again.

400*125M$=50B$. Even 90% are reused in remanufacturing, that's still 4B$ cost. God bless Boeing.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 20, 2019, 06:44:27 am
I would bet it will be back in the air within a few months. Worst case they remove MCAS and re-certify, there appears to be nothing inherently wrong with the aircraft, it just handles a bit differently than the 737 classic. The DC-10 had teething problems that included several deadly crashes within a short period and went on to become a successful aircraft, along wit the MD-11 that evolved from it.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 20, 2019, 08:56:37 am
I would bet it will be back in the air within a few months. Worst case they remove MCAS and re-certify, there appears to be nothing inherently wrong with the aircraft
Problem is that it seems it is unstable and thats the reason for developing the MCAS.
As for the software update it doesn't matter what Boeing comes up with, it will be under harsh scrutiny of pilots, regulatory agencies and airlines worldwide. It may even make its way to Stackoverflow for discussion who knows ::).

It's not unstable, the only problem is the bug in MCAS that makes it push nose down relentlessly for no reason and crash, but not the dynamics of the plane.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 20, 2019, 09:02:29 am
Prediction:  The 737 Max will not fly again.

But that would be game over for Boeing...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 09:07:17 am
But that would be game over for Boeing... 
or the government would have to bail them out from US taxpayers money because it is an to important industry to loose like they did with some banks (so far for capitalism and each should hold up its own).
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 20, 2019, 09:41:26 am
Prediction:  The 737 Max will not fly again.
There’s a precisely zero percent chance of this outcome.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 09:47:46 am
Prediction:  The 737 Max will not fly again.
There’s a precisely zero percent chance of this outcome.
I would not be so sure.
The reputation of the name "737 Max" is already pretty much destroyed.
They might do some small alterations and rename the model to for instance 737 Plus or something like that, in that case mtdoc's prediction has become reality.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 20, 2019, 10:07:30 am
Prediction:  The 737 Max will not fly again.
There’s a precisely zero percent chance of this outcome.
I agree.

I would not be so sure.
The reputation of the name "737 Max" is already pretty much destroyed.
They might do some small alterations and rename the model to for instance 737 Plus or something like that, in that case mtdoc's prediction has become reality.
That could always be a possibility - but I doubt it will go that far.  If Boeing bury the problem name and re-badge the airframe, it is going to be patently obvious as an attempt to hide the embarrassment.  I believe they need to brace themselves and take the flak head on - and I think it is clear they are going to cop some.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 10:25:22 am
It is going to be interesting to see the "game" commence, who is going to resign, who is fired, who is getting the blame.
But in the end Airbus survived their computer-erroneous crashes, so I do not see why Boeing would be different.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: FrankBuss on March 20, 2019, 10:27:04 am
Some rumors about the audio recordings and flight data records:

https://www.reuters.com/article/us-indonesia-crash-exclusive/exclusive-cockpit-voice-recorder-of-doomed-lion-air-jet-depicts-pilots-frantic-search-for-fix-sources-idUSKCN1R10FB (https://www.reuters.com/article/us-indonesia-crash-exclusive/exclusive-cockpit-voice-recorder-of-doomed-lion-air-jet-depicts-pilots-frantic-search-for-fix-sources-idUSKCN1R10FB)

In short: Looks like the nose was pushed down by the trim system and they didn't recognize it, and needed too long to read the manual how to fix it. The evening before another crew had the same problem, but they knew how to fix it, but apparently didn't tell the new crew about the problem.

Isn't there some regulation to report all problems, and for the new crew to read all reports? When I'm watching bus driver changing, they always ask and tell each other if there is a problem with the bus or on the route. I would have thought that's even more verbose for planes.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 20, 2019, 10:44:17 am
No doubt, the pilots are to blame too. After the 610 flight crash they should have known better and disable the damn thing at the first sign.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 20, 2019, 11:04:34 am
It's not unstable, the only problem is the bug in MCAS that makes it push nose down relentlessly for no reason and crash, but not the dynamics of the plane.

I beg to differ, The software was designed to compensate for a new instability that resulted from some small physical-design modification and MCAS was added to comply with airworthiness certification

Exactly. Pushing nose down to decrease AOA and avoid stall is function of MCAS, not bug. Main question here is: it was bad decision of MCAS due to faulty AOA sensor or bad decision of pilots to fight MCAS or maybe both. If instruments scream that stall is imminent, plane itself is pushing nose down to decrease AOA but you gain altitude and speed instead (thus increase AOA) - it is very strange thing to do to say it politely.

[edit] Who the hell runs life-critical system from input of just two sensors single sensor (https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/)?! - Even automobile airbags have better redundancy (AFAIK).
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 11:36:40 am
https://www.youtube.com/watch?v=l0WG0B2JYLQ (https://www.youtube.com/watch?v=l0WG0B2JYLQ)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: LapTop006 on March 20, 2019, 11:59:21 am
The reputation of the name "737 Max" is already pretty much destroyed.

Nah. You'd still fly on a 787 despite the battery fires?

The 777 with engine icing?

What about a DC10 (ok, the final ones are now out of passenger service) after all the cargo door incidents?

The earlier 737s with rudder hard-over?

These things happen with new models, and are usually fixed.

As others have said, the 737MAX is a bit of a hack to keep the line going to compete with the re-engined A320 series, Boeing's plan was to do a fresh design so they could throw away a bunch of the legacy the 737 type certificate, but they decided that would give them a risk of losing customer to Airbus.

Their big hope in this space is probably the MOM airplane plan goes very well, enough to justify a shrink variant that would fit in 737 gates and share a type certificate (similar to the 757/767 days).
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Bud on March 20, 2019, 01:15:34 pm
Both planes crashed in presumably hot climate. Could that have to do with the angle of attack sensors failing?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 20, 2019, 01:41:08 pm
https://www.bloomberg.com/news/articles/2019-03-19/how-an-extra-man-in-cockpit-saved-a-737-max-that-later-crashed (https://www.bloomberg.com/news/articles/2019-03-19/how-an-extra-man-in-cockpit-saved-a-737-max-that-later-crashed)

Quote
As the Lion Air crew fought to control their diving Boeing Co. 737 Max 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit.

That extra pilot, who was seated in the cockpit jumpseat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia’s investigation.

The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.

The presence of a third pilot in the cockpit wasn’t contained in Indonesia’s National Transportation Safety Committee’s Nov. 28 report on the crash and hasn’t previously been reported.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: daddylonglegs on March 20, 2019, 01:56:31 pm
Prediction:  The 737 Max will not fly again.
In the early 90s a design flaw in 737s caused at least two fatal crashes (0) and yet here we are.

Having said that, this time round things might be different. The FAA is seen to be compromised (1):
Quote
As Boeing hustled in 2015 to catch up to Airbus and certify its new 737 MAX, Federal Aviation Administration (FAA) managers pushed the agency’s safety engineers to delegate safety assessments to Boeing itself, and to speedily approve the resulting analysis.

But the original safety analysis that Boeing delivered to the FAA for a new flight control system on the MAX — a report used to certify the plane as safe to fly — had several crucial flaws.

Other agencies will not accept the FAA's certification of the software modification which will cause some delays in the return to flight. The agencies may also reject the FAA's original certification of the 737 MAX and require Boeing to go directly to them for certification (2). If so it will be months or years before the 737 MAX flies in those areas, though it will probably return to flight in the US in a few months.

I recommend reading the Seattle Times article (1). It is hair-raising and what they describe might explain how Boeing chose to activate MCAS off a single sensor even though the why mystifies everyone they asked.

An older article in the same paper (3) discuses the fact that the symptoms of MCAS activation are different to previous runaway trim failures and how this might have flumoxed the Lion Air pilots, both on the accident flight and on the previous flight. That previous flight didn't crash but the pilots were unable to diagnose what was wrong and why what they did worked.

Of course, at this stage we don't know what happened in the second crash and the final verdict is not yet in on the first. The pilots on the Ethiopian flight had information not available to the pilots on the Lion flight.

(0) https://en.wikipedia.org/wiki/Boeing_737_rudder_issues (https://en.wikipedia.org/wiki/Boeing_737_rudder_issues)

(1) https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ (https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/)

(2) https://globalnews.ca/news/5072383/canada-eu-reviewing-certification-boeing-737-max/ (https://globalnews.ca/news/5072383/canada-eu-reviewing-certification-boeing-737-max/)

(3) https://www.seattletimes.com/business/boeing-aerospace/faa-evaluates-a-potential-design-flaw-on-boeings-737-max-after-lion-air-crash/ (https://www.seattletimes.com/business/boeing-aerospace/faa-evaluates-a-potential-design-flaw-on-boeings-737-max-after-lion-air-crash/)

Edit: Apologies, KL27x already posted a link to the main article I was citing.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 20, 2019, 02:02:14 pm
Quote
Mmkaay, now FBI with special counsel Miiuulleeerr and DOJ is setting up a investigation to Russian collusion as they suspect Piutin has caused the MCAS software bug. 2 years later no collusion was found and Miiuulleer refuses to release clown report while Dumpf having tea and cakes with Boing CEO..

I like my tinfoil hats, so fair enough. But wait and see. FAA was fasttracking these approvals because someone was poking/pressuring them and or there was some major personal interest or incentive. Maybe Boeing hires retired FAA officials as consultants, and that is enough. Maybe there's more inbreeding and impropriety than that, even. I imagine Boeing is a very important company to our country's military and government.* And somehow many people were actively not doing their jobs and looking the other way.

*Transportation Secretary Elaine Chao even rode in a 737 MAX two days after the latest crash.

I also like my personal tinfoil hats but that was perhaps not the point, but yes wait and see, but perhaps its more like its to much moo money involved (as usually) to send anyone of the "elite" to jail........................except for that little scape goatee engineer somewhere deep down Titanics boiler room?

Secretary Elaine Chao is more of the symptom of US gov mad cow disease rather then the cure. She was plain luckey! :scared:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: imo on March 20, 2019, 02:25:06 pm
Quote
...
The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.
I can hardly imagine why the crew N1 with such an issues during the flight had not informed the crew N2 on it.
Just watching CNN on new developments on Lion Air case - the pilots were searching in the flight manuals during the dive (from CVR).
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 02:46:02 pm
Quote
...
The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.
I can hardly imagine why the crew N1 with such an issues during the flight had not informed the crew N2 on it.
Just watching CNN on new developments on Lion Air case - the pilots were searching in the flight manuals during the dive (from CVR).

It's very interesting that the Indonesian investigators left out the part about the dead head pilot who knew what he was doing from their report.

Stab runaway is a memory item. That means pilots are supposed to know the procedure, cold.

Evidence is mounting that this system has a design flaw, but the evidence has always been obvious that these crews screwed up.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on March 20, 2019, 03:10:51 pm
Quotes :

“As the 31-year-old captain tried in vain to find the right procedure in the handbook, the 41-year-old first officer was unable to control the plane, two of the sources said.


It is like a test where there are 100 questions and when the time is up you have only answered 75,” the third source said. “So you panic. It is a time-out condition.”


The Indian-born captain was silent at the end, all three sources said, while the Indonesian first officer said “Allahu Akbar”, or “God is greatest”, a common Arabic phrase in the majority-Muslim country that can be used to express excitement, shock, praise or distress. "
  :'(


Reuters : Exclusive: Cockpit voice recorder of doomed Lion Air jet depicts pilots' frantic search for fix - sources (https://www.reuters.com/article/us-indonesia-crash-exclusive/exclusive-lion-air-pilots-scoured-handbook-in-minutes-before-crash-sources-idUSKCN1R10FB)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 03:23:17 pm
There was a frantic search to find out how to disable the trim system because the pilots did not know how to fly the airplane. Stab trim runaway is a memory item. And in the case of lionair, this frantic search was unsuccessful for nearly ten minutes. They were not looking through encyclopedia brittanica here. They would have been looking through a QRH: a laminated, spiral bound book with thumb tabs for common emergencies.

I'm not saying this aircraft did not cause this accident, but this crew's poor performance also caused the accident. Accident chains in aviation almost always have many links.

Reporting on this whole saga has been awful.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MasterTech on March 20, 2019, 03:35:30 pm
There was a frantic search to find out how to disable the trim system because the pilots did not know how to fly the airplane.

Blaming the pilots for *any* of these is mean. Blame Boeing, the FAA, revolving doors, complacency, kickbacks, crony capitalism in the US... take your pick
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SiliconWizard on March 20, 2019, 03:45:01 pm
Quote
...
The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.
I can hardly imagine why the crew N1 with such an issues during the flight had not informed the crew N2 on it.

Although that behavior sounds completely irresponsible to us, I've heard a couple pilots knowing this company saying that it could likely be explained by cultural factors. N1 had a technical problem and managed to solve it on its own. People there tend to suck it up and move on. Reporting a problem they were not 100% sure was a real problem and not something they themselves caused is kinda against they cultural habits.

As to the 737 MAX, frankly it looks like Boeing went one step too far to extend the 737 line. No clue yet whether they are going to get away with it.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 20, 2019, 04:16:24 pm
Blaming the pilots for *any* of these is mean. Blame Boeing, the FAA, revolving doors, complacency, kickbacks, crony capitalism in the US... take your pick

Perhaps not the pilots of the 610 flight, but ET 302 they should have known already and disable the damn thing in a sec at the first sign.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: imo on March 20, 2019, 04:38:29 pm
It's very interesting that the Indonesian investigators left out the part about the dead head pilot who knew what he was doing from their report..
Most probably because a) they had not included the entire 24h long CVR transcript into the report.. [the modern CVRs do 24h recording afaik], or b) they listened to the crew N2 talk only..
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 05:25:04 pm
Blaming the pilots for *any* of these is mean. Blame Boeing, the FAA, revolving doors, complacency, kickbacks, crony capitalism in the US... take your pick

Perhaps not the pilots of the 610 flight, but ET 302 they should have known already and disable the damn thing in a sec at the first sign.

I think this post was made with the tongue firmly in cheek. At least I hope it was!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 20, 2019, 05:44:21 pm
Blaming the pilots for *any* of these is mean. Blame Boeing, the FAA, revolving doors, complacency, kickbacks, crony capitalism in the US... take your pick
Perhaps not the pilots of the 610 flight, but ET 302 they should have known already and disable the damn thing in a sec at the first sign.
I think this post was made with the tongue firmly in cheek. At least I hope it was!

Mine or his?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MasterTech on March 20, 2019, 05:59:27 pm
Blaming the pilots for *any* of these is mean. Blame Boeing, the FAA, revolving doors, complacency, kickbacks, crony capitalism in the US... take your pick
Perhaps not the pilots of the 610 flight, but ET 302 they should have known already and disable the damn thing in a sec at the first sign.
I think this post was made with the tongue firmly in cheek. At least I hope it was!

Mine or his?

LOL, he means your post. Meaning that you can't be serious saying that the ET302 pilots are to blame, in a sarcastic way
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 06:33:43 pm
Blaming the pilots for *any* of these is mean. Blame Boeing, the FAA, revolving doors, complacency, kickbacks, crony capitalism in the US... take your pick
Perhaps not the pilots of the 610 flight, but ET 302 they should have known already and disable the damn thing in a sec at the first sign.
I think this post was made with the tongue firmly in cheek. At least I hope it was!

Mine or his?

LOL, he means your post. Meaning that you can't be serious saying that the ET302 pilots are to blame, in a sarcastic way

I mean that the ET302 pilots certainly are to blame. The aircraft was flyable. They are not the only ones to blame. There's plenty of blame to go around. I don't care if it is "mean" -- I want pilots who can act decisively in an abnormal situation.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 07:07:47 pm
I want pilots who can act decisively in an abnormal situation.
Without prior information and instructions, without proper manual, without proper training ?
So how do you want a pilot to act since something that should not happen, happened and they have no clue that some faulty POS hardware has taken over the plane ?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 20, 2019, 07:39:10 pm
When the MCAS system activates, does it result in the trim wheels spinning or does it occur completely silently? Will a nose up trim command override It or does MCAS have the final say? My understanding is that both trim and MCAS act on the same jackscrew that moves the tailplane.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 20, 2019, 08:18:01 pm
When the MCAS system activates, does it result in the trim wheels spinning or does it occur completely silently?

Yes the wheels spin and make noise, and can be stopped by hand, just have to grab them.

Will a nose up trim command override It or does MCAS have the final say?

Yes a nose up trim command overrides, but as soon as you let the button go MCAS starts trimming again in the other direction, nose down. That's why you have to disable MCAS.

My understanding is that both trim and MCAS act on the same jackscrew that moves the tailplane.

Yes, that's right.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: chickenHeadKnob on March 20, 2019, 08:23:08 pm
Both planes crashed in presumably hot climate. Could that have to do with the angle of attack sensors failing?

It is not self evident why misreads from angle of attack sensors are happening. There is something called density altitude that pilots are very conscious of, it effects take off run distance. Addis Ababa Bole airport is at exceptionally high elevation for a main airport -  2334 meters/ 7625 ft. and is in an equatorial climate zone leading to "hot and high"  conditions and long take off runs. This probably was only a minor factor, the pilots would for sure keep maximum power in climb for some time after lift-off. At other Airports climb power is dialled back for noise abatement  reasons over populated areas.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: jmelson on March 20, 2019, 08:26:35 pm
When the MCAS system activates, does it result in the trim wheels spinning or does it occur completely silently? Will a nose up trim command override It or does MCAS have the final say? My understanding is that both trim and MCAS act on the same jackscrew that moves the tailplane.
The trim wheel spins, and it has a "clacker" to make a distinct noise to inform the crew that it is spinning.  One way to stop trim changes is to GRAB the wheel and hold it, the override clutches are set such that this doesn't take a lot of force.

There are several systems that use the same trim motor in the center console to adjust the stabilizer.  This drives the wheels through a clutch.  the wheels then pull a cable loop that operates the jackscrew in the tail.

Jon
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 08:32:00 pm
I want pilots who can act decisively in an abnormal situation.
Without prior information and instructions, without proper manual, without proper training ?
So how do you want a pilot to act since something that should not happen, happened and they have no clue that some faulty POS hardware has taken over the plane ?

In short: yes. I want the pilot to understand "this machine is doing something I do not want, I must stop it." That is how the the QRH is written, that is how the pilots are (supposed to be) trained: turn of automation and get control of the airplane, figure out why that was necessary later. It's just not a huge mental leap to see that the plane is being trimmed hard down against your wishes, and then to stop that. It really doesn't matter the why and or what "should" happen -- things happen on airplanes. MCAS is not the only reason a plane could have runaway trim, and in fact, the section of the emergency checklist isn't called "MCAS doing crazy stuff" it is called "runaway stabilizer trim." You take action and stop it, just as the dead header the other day did.

I have sympathy for this crew, but they screwed up. It happens.

I actually will have more sympathy for them if they were confused about the true state of the aircraft ("maybe it is stalling and Otto is right to want to go down") because of sensor indications than if they knew the plane was malfunctioning and simply failed to stop it. The former is potentially trickier. But we know from the ET302 flight that this went on for like 10 minutes and through several oscillations. We also know this happened in good VMC so there would be plenty of easy visual indications that the plane was at a reasonable attitude, and, barring any major turbulence or acceleration, that means the AOA would not be high, either. That makes the former less likely and the latter much more.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: langwadt on March 20, 2019, 09:11:07 pm
When the MCAS system activates, does it result in the trim wheels spinning or does it occur completely silently? Will a nose up trim command override It or does MCAS have the final say? My understanding is that both trim and MCAS act on the same jackscrew that moves the tailplane.

https://youtu.be/AgkmJ1U2M_Q?t=3m26s
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on March 20, 2019, 09:23:15 pm
"runaway stabilizer trim."

More like a hobble away in this case.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 10:40:38 pm
In short: yes. I want the pilot to understand "this machine is doing something I do not want, I must stop it."
That is what they did as far as they knew the plane BUT

Quote from: eetimes
After the two recent crashes, public outrage focused on this particular Boeing decision, and on regulatory agencies in the United States and the European Union who agreed that pilots need not be trained or even alerted to the new software, including the new MCAS override controls.

In other words, as far as pilots knew, the MCAS did not exist.

They were not told the main details about their plane, they had no notion of the mcas so they were in a major disadvantage.

You now sound like that board of inquiry from the movie Sully, why did you not directly go to the nearby airport, simulations have proven you could have made it.
Yeah right if you knew right away what was wrong , how much time you had left and made the right decision in a split second.

I find it harsh to blame a dead crew when they had no information about the cause of the problem in the first place. Add the complete confusion because the plane responds totally different than expected.

Quote
That is how the the QRH is written, that is how the pilots are (supposed to be) trained: turn of automation and get control of the airplane, figure out why that was necessary later.
How do you turn something off if no one told you it existed and also not told you how to turn it off, if it can be turned off at all ?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 20, 2019, 10:51:45 pm
How do you turn something off if no one told you it existed and also not told you how to turn it off, if it can be turned off at all ?

They should have known, I mean the pilots of ET 302, because the FAA put out this alert (see the pdf attached) in November 2018 after the Lion flight 610 crash.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 11:08:32 pm
 Lets see what the investigation reveals.
Did they have this AD? They should, but did they?
Which actions did they take and what was the effect?

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 11:09:35 pm
They were not told the main details about their plane, they had no notion of the mcas so they were in a major disadvantage.

Yes, you and others and the media have said this repeatedly. I'm saying something different, as a pilot: it is not relevant. Airplanes at their core, are simple machines. They are objects that are pushed or pulled through the air by engines, and which can change their shape in certain ways to control where they go. That's it. The whole ball of wax. There is a lot of automation in modern aircraft, and pilots, to various degrees, know how it works, or don't. Generally, they know how to use it. They don't know what decisions were made when the software was written, what hidden conditions and failure modes are buried in it. They just don't.

In this case, literally one of the SIMPLEST aspects of the aircraft was out of control: the stabilizer trim. This is controlled, physically, by a prominent and loud wheel in the cockpit, and such wheels are present on just about every aircraft (some trim the elevator, some trim the stabilizer itself). There is nothing mysterious about this.

Better pilots would have stopped this cold.

And as I have said many many times in this thread, that doesn't mean that MCAS is not forked up, or that Boeing didn't screw up. But the pilots still screwed up, and in an obvious way.

You now sound like that board of inquiry from the movie Sully, why did you not directly go to the nearby airport, simulations have proven you could have made it.
Yeah right if you knew right away what was wrong , how much time you had left and made the right decision in a split second.

What is this 10 second nonsense? This plane oscillated more than 20 times over 10 minutes. This is nothing like the Sully movie.

And by the way, I would love to know what Sullenberger would think of this accident. I have a strong suspicion that in pilot's lounges around the world, 737 drivers are mad at Boeing, but also wondering how those crews could have screwed the pooch so badly.

I find it harsh to blame a dead crew when they had no information about the cause of the problem in the first place. Add the complete confusion because the plane responds totally different than expected.

It is harsh. Airplanes are dangerous and judge mistakes harshly. That is the nature of aviation.

How do you turn something off if no one told you it existed and also not told you how to turn it off, if it can be turned off at all ?

Jumpin' Jesus on a pogo stick! They didn't have to turn off the MCAS! They had to turn off the trim system, which of course, they knew about. It's a motor that drives one the basic flight control surfaces of the machine.

(https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/?action=dlattach;attach=682905)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: chris_leyson on March 20, 2019, 11:11:07 pm
If the FAA put out an alert then does it become the pilots responsibility to track FAA alerts or is it the airlines responsibilty to inform the pilots of FAA alerts and provide additional training. Ultimately it is the manufacturers responsibility to inform the airlines and the pilots. Looks like a lack of due diligence on someones part and I don't think it's down to the pilots.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 20, 2019, 11:22:02 pm
Lets see what the investigation reveals.
Did they have this AD? They should, but did they?
Which actions did they take and what was the effect?

If they didn't, it really is the pilots fault (both of them) for not reading required material to maintain their certifications.

Additionally, it would be the Ethiopian airlines fault, as they claimed all their 737 Max pilots received additional training on the MCAS, even before the black boxes were found.

Never mind that this was such current news so much that the general public was aware of it. Airline pilots even more so!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 20, 2019, 11:23:39 pm
Yes, you and others and the media have said this repeatedly. I'm saying something different, as a pilot: it is not relevant. Airplanes at their core, are simple machines. They are objects that are pushed or pulled through the air by engines, and which can change their shape in certain ways to control where they go. That's it. The whole ball of wax. There is a lot of automation in modern aircraft, and pilots, to various degrees, know how it works, or don't. Generally, they know how to use it. They don't know what decisions were made when the software was written, what hidden conditions and failure modes are buried in it. They just don't.

In this case, literally one of the SIMPLEST aspects of the aircraft was out of control: the stabilizer trim. This is controlled, physically, by a prominent and loud wheel in the cockpit, and such wheels are present on just about every aircraft (some trim the elevator, some trim the stabilizer itself). There is nothing mysterious about this.
Better pilots would have stopped this cold.
Well if you are an experienced 737 pilot with thousands of flight hours you probably know best.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 20, 2019, 11:41:07 pm
Yes, you and others and the media have said this repeatedly. I'm saying something different, as a pilot: it is not relevant. Airplanes at their core, are simple machines. They are objects that are pushed or pulled through the air by engines, and which can change their shape in certain ways to control where they go. That's it. The whole ball of wax. There is a lot of automation in modern aircraft, and pilots, to various degrees, know how it works, or don't. Generally, they know how to use it. They don't know what decisions were made when the software was written, what hidden conditions and failure modes are buried in it. They just don't.

In this case, literally one of the SIMPLEST aspects of the aircraft was out of control: the stabilizer trim. This is controlled, physically, by a prominent and loud wheel in the cockpit, and such wheels are present on just about every aircraft (some trim the elevator, some trim the stabilizer itself). There is nothing mysterious about this.
Better pilots would have stopped this cold.
Well if you are an experienced 737 pilot with thousands of flight hours you probably know best.

That's literally not an argument.

As I've stated upthread, I am a pilot, not an airline pilot. I fly much simpler aircraft. Yet even in those aircraft there are sophisticated autopilots and I know how to disable them.

I'll tell you one thing I probably have in common with those guys: I don't want to die in an airplane crash. To that end, I think quite a bit about what I'd do in a given situation, whether I'd be up to it or not. I, of course, don't know. But to take a ship into the air, one should at least try to approach the question honestly. Most, but not all, pilots read a LOT about accidents. They study the mistakes of others. In the process, you come across some where you're pretty sure you wouldn't make that mistake, others where you see yeah, I would be susceptible to that. In the end, of course, until you're tested, you just don't know. But you still think about it. You still analyze, try to predict, try to mentally prepare. And to the best of my non-737 driver ability to predict, I think most competent pilots would have flown through these upsets. Maybe scared, maybe angry, but they would have kept control. That opinion is worth just as much as yours, no more, no less.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 01:27:59 am
Quote
And to the best of my non-737 driver ability to predict, I think most competent pilots would have flown through these upsets. Maybe scared, maybe angry, but they would have kept control. That opinion is worth just as much as yours, no more, no less.
I think if you put the world's 100 best 737 commercial pilots in this situation, without any knowledge of MCAS, a significant percentage of them would have failed. The most important bit to me, is if Boeing has disclosed the specifications of the MCAS system to its customers, this could have dropped to practically zero (in this exact scenario, anyway... it could have been much worse). Sure, some better pilots would have shut off the stab trim before the final super malfunction from the double-triple hit of MCAS. Some much worse pilots would have, as well. But it was probably avoidable in the first place.

Quote
What is this 10 second nonsense? This plane oscillated more than 20 times over 10 minutes. This is nothing like the Sully movie.
And during that 10 minutes, the MCAS fired 21 times. So during that 10 minutes, the plane was bucking violently more than half that time. That makes it a bit more difficult to use the emergency manual. Every time the thing went off, the pilot had seconds to correct the plane, rather than reading a manual. No matter how great it is organzed, it will be hard to use under these conditions.

This is what I consider a fact: The stab cutout switches were never designed to handle this kind of event. A system that can erroneously adjust the trim to 50% of a full nose dive per activation should need to be automatically or easily deactivated from the main control column or yoke. This MCAS could theoretically erroneously fire at ANY altitude, as far as we know. It may not even be recoverable at all if it happened during takeoff or landing.

Consider the FO took control, having just lived through 21 of these events. And the very first time it happened under his control (he got a double whammy, apparently), the plane was not recoverable even from a mile up.



Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 21, 2019, 01:35:16 am
They were not told the main details about their plane, they had no notion of the mcas so they were in a major disadvantage.

Yes, you and others and the media have said this repeatedly. I'm saying something different, as a pilot: it is not relevant.

I'm not a pilot, but I understand enough to see the validity of the above statement.  The symptom of a stabilizer going crazy is all that matters in determining the action required.  The cause is pretty much irrelevant when you are trying to control the aircraft and you already have a procedure in place to deal with the problem.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 21, 2019, 01:36:38 am
This is what I consider a fact: The stab cutout switches were never designed to handle this kind of event.

Then why were they fitted?  (To me, the answer is really obvious.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 01:46:12 am
^ to me the it is obvious that shutting off the autopilot was made more easy and intuitive than cutting out those stab trim switches. The dual stab trim switches are there for a reason.... just in case the first part fails. And in the original 737 design, the only thing automatically adjusting the trim would have been an autopilot thing, making small but persistent adjustments, not a full on nose dive at over 1G, losing significant altitude that takes time to regain.

If the MCAS were disclosed, cutting out the stab trim switches would not be a secondary action in this instance of violent downward trim. You do not have time to even do that if this error happened at low enough altitude and it would be very difficult to take your eyes off the ground to flip switches on the ceiling if it happened out of the blue at low altitude and you are in an unexpected free fall.

If it's the second action on a paper in flight emergency reference manual, it works better if you have time to refer to the manual before you are dead. Esp if you are a seasoned 737 pilot who has learned all the important bits of the 737, and then you are told the MAX is exactly the same.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 21, 2019, 01:47:55 am
this guy is a programmer and a (cessna) pilot and seems to think the core problem is, that what should have been a brand new aircraft design was being sold as a 737 still.

https://drive.google.com/file/d/1249KS8xtIDKb5SxgpeFI6AD-PSC6nFA5/view?fbclid=IwAR0CXP2xVmFT2pSGMmx519uFmRw7jMs9uq5FnrumIqT34KcS8j5of5bTWa8 (https://drive.google.com/file/d/1249KS8xtIDKb5SxgpeFI6AD-PSC6nFA5/view?fbclid=IwAR0CXP2xVmFT2pSGMmx519uFmRw7jMs9uq5FnrumIqT34KcS8j5of5bTWa8)

And as a result of this corporate sleight of hand, it has a very unstable airframe, which is patched by an added software system that the 737 never had before, and safety is signed off by someone in the aircraft manufacturer's employ, with a huge conflict of interest.

Added bonus, it seems like the auto control software was written by a siloed off group that has no practical experience with flying planes, and certainly no understanding of the fragility of mechanical sensors.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 21, 2019, 02:10:13 am
If the MCAS were disclosed...

You are still not getting the point.

The symptom was runaway stabilizer.  There is a predetermined set of actions to be executed in such a situation - and, from what I have seen, these are memory items - NO MANUAL LOOKUP REQUIRED.

You could list a dozen causes for a runaway stabilizer problem - one of which may be MCAS - but exactly which one does not matter when it comes to taking remedial action.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 21, 2019, 02:15:12 am
And in the original 737 design, the only thing automatically adjusting the trim would have been an autopilot thing, making small but persistent adjustments, not a full on nose dive at over 1G, losing significant altitude that takes time to regain.

Pretty sure that's not true. There are two things that, without MCAS, are *supposed* to cause the stab trim to move: the pilots trim switches and the autopilot. But if their is a fault in either of those, or the wiring between them and the motors, or if there is a mechanical fault in the system, then the system can go haywire. (The reason it has that grasp and hold item in the checklist is in part because there are mechanical failure modes where unit can move on its own, and the pilots can stop it.) Again, the procedure outlined in the FCOM/QRH is to stop the trim from moving, and it just doesn't ask or even mention anything about the cause.

If the MCAS were disclosed, cutting out the stab trim switches would not be a secondary action in this instance of violent downward trim. You do not have time to even do that if this error happened at low enough altitude and it would be very difficult to take your eyes off the ground to flip switches on the ceiling if it happened out of the blue at low altitude and you are in an unexpected free fall.

I think basically the first part is true: if the pilots were aware of MCAS, they would have been more likely to act to shut out the trim motors. However, the ET pilots did know this (or could have) and didn't, so there is also a training requirement. The second part about time is still dubious to me. MCAS actually us unlikely to activate near the ground as it cannot operate when flaps are out. So you'd have to be near the ground due to something weird happening already for MCAS to be a factor there.

Also, the switches are on a lower console, not that it matters,

If it's the second action on a paper in flight emergency reference manual, it works better if you have time to refer to the manual before you are dead. Esp if you are a seasoned 737 pilot who has learned all the important bits of the 737, and then you are told the MAX is exactly the same.

Pretty sure the stab runaway procedure is *supposed* to be a memory item, meaning the pilots should know it. But the book exists because nobody remembers everything in an emergency. But again, this is not an ordinary book. It is designed to be used in an emergency, and has large type, thumb indexed sections, red to outline the emergency stuff. The idea is that while one person is handling the aircraft, the other can grab this and get critical information out of it. Whether this is true in practice, I don't know. But it is  definitely intended that pilots can quickly access emergency procedures.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 02:19:02 am
Quote
You are still not getting the point.
I get it.

Quote
- and, from what I have seen, these are memory items - NO MANUAL LOOKUP REQUIRED.
I'll concede this, even. Djaco seems to agree on this.

But a 737 pilot with 5,000 hours of training on a 737 and countless more hours of simulation, they expect certain things. This was not expected. Do you appreciate what 2.5 degrees of stab trim means (per activation)? See the vid of the MAX doing a stunt takeoff. 2.5 degrees is half the total trim, and it can erroneously retrigger, giing it unlimited authority. This is not something expected. And it happened at a low enough altitude to be a real gut check.

If this happened while a plane happened to be banking in a tight enough turn at low enough altitude in approach maneuvers, it might not even be recoverable. Your first automatic response after flying 737 forever would be to cut out autopilot and correct manually. Then you get hit with the multiple erroneous activations, and it is too late to fix that, at all.

*Djacobow: yeah, I don't know at what altitude you extend/retract the flaps, but apparently even a mile up does not give a lot of time. 20-25 seconds to impact, maybe the last 10 to 15 could be too late to correct.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 21, 2019, 02:31:56 am
But a 737 pilot with 5,000 hours of training on a 737 and countless more hours of simulation, they expect certain things. This was not expected.

I think this is where our arguments diverge - the identification of the problem.  As I understand it, one of the purposes of simulation time is to train and keep pilots "up to speed" in identifying and resolving abnormal situations.

Real life doesn't always play nice, presenting you with familiar, practiced scenarios - but, rather, will add its own twists.  This is why I am not going to pursue the point any further and I will see what comes from the investigation.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 21, 2019, 02:32:31 am
I want pilots who can act decisively in an abnormal situation.
Without prior information and instructions, without proper manual, without proper training ?
So how do you want a pilot to act since something that should not happen, happened and they have no clue that some faulty POS hardware has taken over the plane ?

In short: yes. I want the pilot to understand "this machine is doing something I do not want, I must stop it." That is how the the QRH is written, that is how the pilots are (supposed to be) trained: turn of automation and get control of the airplane, figure out why that was necessary later. It's just not a huge mental leap to see that the plane is being trimmed hard down against your wishes, and then to stop that. It really doesn't matter the why and or what "should" happen -- things happen on airplanes. MCAS is not the only reason a plane could have runaway trim, and in fact, the section of the emergency checklist isn't called "MCAS doing crazy stuff" it is called "runaway stabilizer trim." You take action and stop it, just as the dead header the other day did.

I have sympathy for this crew, but they screwed up. It happens.

I mean that the ET302 pilots certainly are to blame. The aircraft was flyable. They are not the only ones to blame. There's plenty of blame to go around. I don't care if it is "mean" -- I want pilots who can act decisively in an abnormal situation.

I would wait to draw such conclusions. Its guaranteed what pilots have said regarding 737MAX (is that a new STM32F model?) will be one of the hot points when this debacle mangles in the courts. From NASA pilot safety database: https://asrs.arc.nasa.gov/search/database.html

Quote
The airplane’s nose can tilt down suddenly during takeoff, pilots aren’t being adequately trained on the autopilot system, and the operations manual is “criminally insufficient.” These are the complaints of US pilots in incident reports involving Boeing’s 737 Max 8 jetliner, the same model that was involved in two deadly crashes in recent months.

Another pilot said it was “unconscionable that a manufacturer, the FAA, and the airlines would have pilots flying an airplane without adequately training, or even providing available resources and sufficient documentation to understand the highly complex systems that differentiate this aircraft from prior models.”

That same pilot added, “I am left to wonder: what else don’t I know? The Flight Manual is inadequate and almost criminally insufficient. All airlines that operate the MAX must insist that Boeing incorporate ALL systems in their manuals.”

After the Lion Air Flight 610 crash, Seattle Times has published an article that Boeing did not inform companies or pilots that they even installed the system. This means that pilots had no knowledge about MCAS and its processes.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 02:39:41 am
In the words of Mike Tyson, "Everyone has a plan, until they get punched in the face."   
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 21, 2019, 03:26:29 am
Prediction:  The 737 Max will not fly again.
There’s a precisely zero percent chance of this outcome.
I would not be so sure.
The reputation of the name "737 Max" is already pretty much destroyed.
They might do some small alterations and rename the model to for instance 737 Plus or something like that, in that case mtdoc's prediction has become reality.
There is literally zero, null, nada, zilch chance that it won’t take to the skies again (with the same name). Though the crashes are terrible, the cause is fairly simple and will be simple to fix. As others have explained to you already, many aircraft models had early issues, but later went on to be reliable, safe workhorses.

This isn’t a comparatively cheap product like a smartphone where a complete recall costs “just” a few billion dollars. This was $2-3B in development alone, and then each aircraft costs $121 million, and they delivered 350 units so far. A permanent recall would thus cost a total of $45.4 billion. It’s not gonna happen, especially since the fix will be very inexpensive.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 04:25:00 am
Even after disabling stab trim and turning the wheel manually to narrowly avoid the first impact, the pilot would have probably stalled the fully loaded plane in tbe process, believing it to be able to lift and handle like a regular 737.

This is the exact scenario where properly functioning MCAS is necessary to make 737 pilots qualified to fly the MAX.

If Boeing had let this cat out of the bag, pilots would have needed to learn how to manually fly a 737 MAX, and it would have required another 9 months to a year for certification. They could not even acknowledge this difference to their customers. There's no way a 737 pilot would have known to jam the trim a whole 2.5 degrees when the stick shaker went off.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 21, 2019, 04:42:41 am
Even after disabling stab trim and turning the wheel manually to narrowly avoid the firat impact, the pilot would have probably stalled the fully loaded plane in tbe process, believing it to be able to lift and handle like a regular 737.
What?!? The whole issue with the engines is that the MAX has too much lift, not too little. MCAS’s job is to nudge the nose back down, not up.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 04:47:48 am
Quote
What?!? The whole issue with the engines is that the MAX has too much lift, not too little. MCAS’s job is to nudge the nose back down, not up.
The reason for this is because the MAX will easily enter an unrecoverable stall if you are at a high angle of attack, which would not happen with the previous versions. You would be using a high angle of attack when pulling up from an unexpected dive at low altitude. And you would have to deactivate MCAS to do this. The pilot would be manually flying a plane that handles very differently and stalls much easier than the plane he was certified on. The new plane was slipped under the same certification because of this MCAS system.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 21, 2019, 05:11:44 am
Even after disabling stab trim and turning the wheel manually to narrowly avoid the firat impact, the pilot would have probably stalled the fully loaded plane in tbe process, believing it to be able to lift and handle like a regular 737.
What?!? The whole issue with the engines is that the MAX has too much lift, not too little. MCAS’s job is to nudge the nose back down, not up.

You focused on the wrong aspect of the word "lift".  It was not the magnitude of the lift force that was intended in the cited statement, but the aspect of "lift and handle" (perhaps better stated as just "handle") "like a regular 737".

The point being that when thrust is added in the MAX, it has a (significantly) greater upward turn moment than that of earlier models of 737.  This will cause more pitch up than a pilot used to the older models would expect ... ie. it does not handle "like a regular 737".
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 05:19:51 am
^No not just that. According to Djacobow, the aerodynamics of the engines, themselves, increase the lift as the AOA increases. So as the AOA increases, the AOA increases itself. In order to utilize the same high angle of attack in the MAX, the pilot would have to know how the plane handles to "ride the edge." They would have to preemptively trim down (a huge amount!) to maintain that high AOA in a way that it doesn't run away from them. I imagine it is a bit like countersteering in a car where the back end can break loose. If you don't expect it, you are probably going to spin around and go over the edge of the cliff.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 21, 2019, 05:38:52 am
You guys are going in circles. Some of you need to stop assuming pilots are idiots if not properly trained on the aircraft. Stop saying stupid things like pilots automatically will stall the plane if the system isn't on. They still have basic flying skills that apply to all planes to fall back on. Arguments about what constitutes certification doesn't make the pilots incompetent and unable to react to the consistent and controllable effects of engine thrust, even on manual control.

Clearly Boeing expected the plane to be flyable with the automatic trim system disabled, or the procedure wouldn't be in the manual and the stab cutout switches wouldn't exist.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 05:53:40 am
^LOL okey doke.

Of course manually flying the plane is better than the plane in permadive. But controlling the plane in a high AOA would have been extremely difficult for someone who has trained on the old plane and handed this one that is supposed to be no different.

The original plane was designed from the start to be stable. The change in engine made it unstable at high AOA. Pilot can't be expected to use a high AOA for the first time in an emergency situation and magically "feel" the angle getting away with adrenaline coursing (and lol if you think they are going to be determine this by sensor readings in real time), and knowing to respond so quickly and drastically to maintain control of the plane. 
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 21, 2019, 05:54:27 am
The reason for this is because the MAX will easily enter an unrecoverable stall if you are at a high angle of attack, which would not happen with the previous versions.

Stall characteristic of MAX is the same as NG. What's different - increased pitch up effect of the LEAP-1B engines due to their placement (forward & up). Pitch-up increases AOA which may lead to stall.

Quote
The new plane was slipped under the same certification because of this MCAS system.

MCAS system was introduced to slip MAX under "minor modification of existing plane" certification. Boeing was cutting corners on self-certification (allowed by FAA) because of competition from Airbus. 737 NG - licensed pilots were trained for MAX on iPads during 1-hour session. No simulator session required :palm: This is criminal negligence from Boeing, regulators and airlines: https://www.aviationcv.com/aviation-blog/2019/shocking-facts-boeing-737max-crash (https://www.aviationcv.com/aviation-blog/2019/shocking-facts-boeing-737max-crash)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on March 21, 2019, 05:58:13 am
Some of you need to stop assuming pilots are idiots if not properly trained on the aircraft.

+1 , this  :-+

Some sound so convinced that like they're actually have been in the cockpit watching the whole scenery.  :palm:
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 06:03:59 am
Quote
Stall characteristics of MAX is the same as NG. What's different - increased pitch up effect of the LEAP-1B engines, their placement (forward & up). Pitch-up increases AOA which may lead to stall.
But additionally, at high angle of attack, the engines themselves aerodynamically produce lift and drag. At high angle of attack, the plane isn't flying nose first. The vector of travel is at an angle to the attitude of the plane. And larger engines further forward is like an "air brake" giving the effect of the plane wanting to flip/rotate. This is very pronounced. We know this because of the degree of trim movement that MCAS needed to make.

In the original plane, as designed, this high AOA would be stable. On the MAX the problem is not inadvertently nosing the plane up due to thrust. Otherwise, MCAS would adjust the trim a tiny bit according to the amount of thrust. It's the problem of what happens to the plane once it is at a high angle of attack which MCAS addresses. At this point the plane is unstable and wants to spin in the air, tail under nose. That's the direction of force that the engine placement creates in this attitude.

Quote
Stall characteristics of MAX is the same as NG.
If it handled just like the NG, there would be no need for MCAS. The normal response would be sufficient.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 21, 2019, 06:06:20 am
At high angle of attack, the plane isn't flying nose first.

Right.  :-DD
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 06:11:31 am
What I mean is the plane isn't flying like an arrow. A high AOA would be a situation where the nose is tilted up and the back end of the fuselage passes through a lower point in space than the nose of the fuselage.

When the plane is puling up hard from a dive, it doesn't reach level flight the instant the plane's fuselage is horizontal to the ground. The vector of the plane will still be such that the plane is losing some altitude at this point.

This is what high AOA means, don't it?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 21, 2019, 06:24:38 am
At high angle of attack, the plane isn't flying nose first.

What? I think it sums it up pretty nicely. Angle of attack of 0° means the plane is flying perfectly nose first. As in the plane is pointing in the same direction as its air speed velocity.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 06:48:36 am
^I don't know if Berni is backing me up or piling on. But I fully agree with his statement.

I'm not a pilot and I'm not trying to school anyone. I'm just using common sense. Just because you're not a pilot doesn't mean you have to take words like AOA and treat them like a made-up thing in Star Trek.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 21, 2019, 06:54:28 am
At high angle of attack, the plane isn't flying nose first.

What? I think it sums it up pretty nicely. Angle of attack of 0° means the plane is flying perfectly nose first. As in the plane is pointing in the same direction as its air speed velocity.

No, it doesn't. You're confusing angle of attack with pitch. In a straight and level cruise, you're still going to need a positive angle of attack to counter the force of gravity.

Angle of attack is the difference between the chord of the wing and the actual direction of travel. Note that flaps, when deployed, change the shape of the wing which changes the chord of the wing which changes the angle of attack relative to the pitch of the plane. Similarly, spoiler devices on the wing can spoil the lift, which doesn't actually change the chord, but does change the angle of attack because it affects the direction of flight.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 06:59:26 am
^Ok. Take everywhere I said AOA and change it to pitch.

So "pitch" is the angle of the plane relative to the vector of the plane's velocity, not an angle in relation to the earth, right? And for simplicity, I'm not worried about wind.

The engines being fixed to the plane, w/e you call it, this is the problem I'm referring to. As the angle of the plane increase upwards in relation to its vector, there is a point where the MAX will be unstable and will quickly go out of whack beyond recovery in a positive feedback loop (at least compared with the original version). This is what seems obvious to me from what we have been told and including what Djacobow has previously explained a few pages back.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rs20 on March 21, 2019, 07:09:22 am
Everyone here is being overly specific. Let's start by quoting wikipedia.

Quote
In aerodynamics, angle of attack specifies the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. Since a wing can have twist, a chord line of the whole wing may not be definable, so an alternate reference line is simply defined. Often, the chord line of the root of the wing is chosen as the reference line. Another choice is to use a horizontal line on the fuselage as the reference line (and also as the longitudinal axis).

OK, so:
1. Angle between the longitudinal axis of the aircraft and earth (irrespective of direction of travel): is called Pitch (so KL27x, the answer to your last question is "No, pitch *is* related to the earth")
2. Angle between the longitudinal axis of the aircraft and the velocity of the aircraft through the air: is called AOA (assuming we choice the "another choice" in the Wikipedia definition); and needn't be positive in straight and level flight (especially at high speed)
3. Angle between root chord of the wing and velocity of the aircraft through the air: is also called AOA (assuming the chord line definition is used); and this particular definition I could believe Nusa's claim that this must always be positive in straight and level flight, maybe.

In short, let's stop arguing over an ill-defined term like AOA. A wing designer probably has definition 3 in mind, while a pilot maybe probably has definition 2 in mind.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 21, 2019, 07:28:02 am
Ah it is a confusion with pitch. No, pitch and AOA are two different things.

Pitch is the front to back angle of the plane relative to horizontal on earth. It makes up the absolute rotation angle along with Roll (angle left to right relative to horizontal) and Yaw (rotation around the planes vertical axis relative to the earths north pole).

This is much like mixing Yaw and Heading. Heading is also relative to the north pole, but its the direction the plane is moving. Wind causes the difference between the two as crosswind essentially makes the plane fly slightly sideways relative to the ground below (This is seen nicely in heavy crosswind landings)

AOA is the angle of the difference between your Pitch Roll Yaw of your plane and the direction of the wind outside (Tho usually you only want AOA to be offset in the Pitch direction). Its essentially what angle the air is hitting the wings. You want a few degrees of AOA for the wings to produce lots of lift, but if the AOA gets too high the wings go into a so called aerodynamic stall where the lift drops sharply, the drag sharply raises and heavy turbulence develops around the wing. This is very bad because no lift means you fall out of the sky and because the wings are now ineffective its very difficult to control the plane to get it pointing forwards again so that the AOA reduces and you get lift again.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 07:34:14 am
I'm pretty happy with those explanations. I think my previous posts are fairly ok, then.

Regardless if perfectly horizontal flight means the AOA must be positive, that is irrelevant. When pulling up out of a nose dive to avoid crashing the plane into the ocean, one would expect the plane to be put into a high AOA. And this is where the MCAS would kick in to prevent the 737-trained pilot from losing the plane to a stall.

So in the case of having to shut off MCAS because the plane it put into a nose dive with an imminent date with the earth, the pilot would then be putting the 737 MAX into a high AOA and facing the dangerous potential of a stall. Crash into the ocean at 600mph, or fall into the ocean at 200mph. Dead is dead.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 21, 2019, 08:05:24 am
The thing is that this MCAS system would take a while to adjust the trim so low that the plane would nose dive into the ground.

The pilots would have seen the big trim wheels moving as MCAS is trimming pitch down. The wheels also make a mechanical noise as they spin on purpose to make them more noticeable. All they would have to do is flick a switch to disable automatic trim, manually trim it back to level and then continue flying as normal.

But the fact that the pilots are not properly trained about the new MCAS and its possible failure modes, likely means that the pilots are suddenly suspecting other failures and reacting according to those, the high stress situation making them too focused on certain things that they would not notice the trim wheel oddity. There are many many things that can go wrong on a plane, troubleshooting a system you don't even know exists on such short notice as you are heading for the ground is not easy.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 21, 2019, 08:12:17 am
New update. This man is probably the best subject-matter-expert reporter available for interpreting the actual facts released from various sources:

https://www.youtube.com/watch?v=9Ts_AjU89Qk (https://www.youtube.com/watch?v=9Ts_AjU89Qk)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 08:24:00 am
^8:23 for insight over MCAS and the interesting perspective that a third pilot might bring.

Quote
There are many many things that can go wrong on a plane, troubleshooting a system you don't even know exists on such short notice as you are heading for the ground is not easy.
Exactly. And even though the problem went on for 10 minutes in the Jakarta case, think how near these "single" spaced out malfunctions would put the plane to death that entire time. In the fully loaded plane, you would lose altitude much more quickly than regaining it. It only took the one double malfunction in rapid succession to end it all. The captain took back control but it was not in time. You know he wasn't taking a nap. He was right there, trying to save everyone's life.

Quote
The thing is that this MCAS system would take a while to adjust the trim so low that the plane would nose dive into the ground.
Did you see the altitude graph? I imagine everyone on the plane lost their lunch. These changes don't appear to be gradual. This guy ^ uses the words "absolutely terrifying." "Startle factor." No matter how big the wheel or how loud it clicks, it appears to be quite responsive. See the vid someone posted of the vertical takeoff, how fast it can level out. Just because it is normally steered like the Titanic doesn't mean it can't change vector in a hurry. I imagine the MCAS system would be moving the elevator as fast as possible. The runaway trim which pilots have been trained and done simulation with is never going to move the elevator that much or that fast, lest someone spill their drink. Only 5 degree change needed for full nose dive, per the Seattle Times article, and the MCAS does 2.5 degrees per firing. How much of that elevator range did the test pilot in the stunt takeoff use? Was that even full elevator?

I refuse to believe that 2 out of 2 pilots can get a job flying a hundred million dollar plane with 200 souls on board without being halfway competent.

*You can also see in this video the location of the AOA sensor is on the sides of the plane near the nose. Thus, the AOA, as measured by these vanes, is the angle of the plane vs the air it is passing through. It is only measuring the angle of the "wings" by virtue that the wings are attached to the fuselage. So I don't get the hubbub over my usage of AOA. I didn't think modern commerical jets rotate their wings to adjust AOA. They may have some control surfaces to change the curvature of the top of the wing to change the amount of lift. And there are flaps. But the wings are pretty fairly well fixed in place, otherwise.

Tooki: the pilot in this video states what you did, as to the reason for MCAS. That it is there because the position of the engine produces substantial nose up force. But we know by virtue of how it works, this is not correct IMO. It kicks in based on AOA sensor. It only kicks in after the nose has gone up. It is not there to make the plane handle like a 737. With the MAX, the pilot can get the nose up by increasing thrust. This isn't counteracted by the elevator under normal AOA. It's only when the AOA gets extreme that it kicks in. So as long as the AOA is not nearing the danger zone, yeah, the nose goes up under hard acceleration. No magic prevents this from happening. The magic pixies kick in if this goes too far out of the normal range. IOW, the MAX can't necessarily pull up with greater force than the NG. The elevator can do that just fine; the engines need not do this at all. What this means is the MAX loses control.... if not before, at least more suddenly... than the NG does.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 21, 2019, 10:23:00 am
Why did none of the pilots at least grab and stop the trim wheel? I still don't get it. The damn thing was spinning under their noses. They knew what that wheel spinning meant, didn't they? Three minutes is a long time, it's not a sec, yet they couldn't connect the dots. Poor guys. It's so sad.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 21, 2019, 10:30:03 am
Three minutes is a long time...

In a confusing, high stress, life and death situation, 3 minutes will pass very, very quickly.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 21, 2019, 10:30:20 am
Quote
The thing is that this MCAS system would take a while to adjust the trim so low that the plane would nose dive into the ground.
Did you see the altitude graph? I imagine everyone on the plane lost their lunch. These changes don't appear to be gradual. No matter how big the wheel or how loud it clicks, it appears to be quite responsive. See the vid someone posted of the vertical takeoff, how fast it can level out. Just because it is normally steered like the Titanic so no one spills their drink doesn't mean it can't change vector in a hurry. I imagine the MCAS system would be moving the elevator as fast as possible. Only 5 degree change needed for full nose dive, per the Seattle Times article. How much of that did the test pilot in the stunt takeoff use? Was that even full elevator?

Well yes you can certainly make negative G or pull over 2G in a big airliner if you try.

But the quick maneuvers are done using the control surfaces moved by powerful hydraulic pistons, these are the ones tied to the pilots control column and can certainly move very fast. But things like trim are different, here the entire wiglet on the tail moves. This is moved via a motor turning a worm gear, all this gearing down gives it plenty of oomph while turning very slowly, as in normal use it is never needed to turn quickly. This is what MCAS is moving via trim.

The problem is that the entire wiglet is much bigger than the small flap part at the end of it. This small flap is what is moved quickly and responsively by hydraulics. If the whole wiglet is tilted up a little bit then you can just tilt down the flap to counteract it, but once the wiglet tilts more it can produce more force than the little flap can at full deflection. At this point no matter what the pilot does on the control stick he can't get the nose back up (Well apart from rolling the plane on its back, but then you have a uncontrolled pitch up and its certainly not something you are supposed to do in an airliner, especially if you ask the passengers).

The two fighting forces of the wiglet and its flap also produce more drag, slowing the plane down, making it even harder to keep altitude.

Keep in mind that the pilot can keep it perfectly level while the trim is being turned down by simply pulling back on his controls more and more. But eventually he hits the end of his control range and that's when the plane starts to plummet. (Tho if the plane was warning him of a stall he might not pull up since that's the opposite of what you are supposed to do if approaching a real stall)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: TerraHertz on March 21, 2019, 10:54:58 am
https://www.rt.com/news/454275-indonesia-crash-third-pilot/ (https://www.rt.com/news/454275-indonesia-crash-third-pilot/)
Off-duty pilot reportedly saved Boeing 737 MAX from crashing day before disaster
Extract:
Quote
An extra pilot, who hitched a ride on a Lion Air Boeing 737 MAX a day before its crash in October, saved it during an emergency strikingly similar to the one that proved fatal, Bloomberg reports.

The new airliner plunged into the Java Sea killing all 189 people on board apparently due to a malfunction in an anti-stall system which pushed the nose of the aircraft down.

A day before the crash the same aircraft experienced a similar problem but was saved by an off-duty pilot who realized what was happening and instructed the crew on how to stop the system from affecting the flight, the agency said.

I wonder if the MCAS software interprets 'rapidly declining altitude' as 'must be still stalled, try more pitch down' ?
Also, with all the spoken warnings to pilots in modern cockpits, you'd think someone would add some spoken messages from MCAS, to let pilots know why the 'safety system' was killing them.
Though given the attitude inherent in implementing something like MCAS (rather than just warning the pilots), such a message would probably be something unhelpful like "I hate you, die die dieeeee!"


This is why I refuse to own a car with computerized engine and drive systems. Well, ONE reason why.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 11:18:08 am
Berni, I wonder where you are getting this information that is not in the news? Are you interested in aviation or do you have personal experience?

Google "737 winglet" and it says this is the little vertical thing at the tips of the wings. The elevators appear to me as one piece on either side of the tail. As far as I know, the elevator is the most powerful control surface for rapidly changing the attitude/AOA of the plane under normal flight. And the same elevator used by MCAS or by autopilot trim is also used by the pilots for manual control.

GeorgeoftheJungle, in my understanding, everyone who is talking about the trim wheel slowly clicking away until the snoozing pilot realizes his plane is facing the ground is not on the right planet. This kind of incident might have surprised the pilots the first time, but not the 22nd time. If the wheel makes a clicking sound, maybe watch a video of a Marlin fisher and the sound the reel makes when the fish is pulling away at 50 knots. When this happened, the pilots didn't need to hear the clicks to suspect something was wrong. Their seats falling out from under them and their lunch pushing into their esophagus provided all the notice they needed. If that didn't work, I'm sure the 200 screams would have woke the dead. This is not a gradual trim adjustment or course change. It's a last ditch massive response for when the S has already HTF, and all the drinks have already been spilled.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 21, 2019, 11:38:22 am
Google "737 winglet" and it says this is the little vertical thing at the tips of the wings.

I think he did mean horizontal stabilizers. Indeed it would be good that we do not re-invent naming of airplane parts & systems
https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/ (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 12:05:08 pm
There are control surfaces on the wings for banking. There are flaps on the wings for increasing lift and drag during takeoff and landing. There are sliding surfaces on the top rear of the wing for changing the amount of lift.

Don't let the words "trim" or "stabilizer" fool you. The elevators are the most powerful control for changing the plane's vector. If you want to do a loop de loop or a rapid nose dive, you use the elevators.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Berni on March 21, 2019, 12:09:34 pm
Yes the technical term for that part of the tail is the elevator but i wanted to stick to generic terms. So winglet as in "a small wing shaped thing" rather than those little upwards curving things on the end of wings, but yeah those are indeed called winglets (Unintended name clash).

I do have some interest in aviation and work at a company that makes avionics, but i am not a pilot, so don't take my words as fact.

Was mainly trying to explain why trim does not cause the plane to suddenly nose dive out of the blue within a second, but rather its a slow gradual thing that makes the plane more and more nose heavy as time goes on until at some point it becomes impossible to keep it up by normal control column input.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 21, 2019, 12:21:07 pm
There are control surfaces on the wings for banking. There are flaps on the wings for increasing lift and drag during takeoff and landing. There are sliding surfaces on the top rear of the wing for changing the amount of lift.

Don't let the words "trim" or "stabilizer" fool you. The elevators are the most powerful control for changing the plane's vector. If you want to do a loop de loop or a rapid nose dive, you use the elevators.

If that were true, we wouldn't be in this situation. In fact, the elevators are the second-most powerful control for that purpose, having less surface area than the horizontal stabilizer itself. Part of the reason the stabilizer jackscrew has that much travel is that it's intended to serve as a backup system for a jammed or inoperative elevator. In normal operation, the two systems work together.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 21, 2019, 12:30:08 pm
GeorgeoftheJungle, in my understanding, everyone who is talking about the trim wheel slowly clicking away until the snoozing pilot realizes his plane is facing the ground is not on the right planet. This kind of incident might have surprised the pilots the first time, but not the 22nd time. If the wheel makes a clicking sound, maybe watch a video of a Marlin fisher and the sound the reel makes when the fish is pulling away at 50 knots. When this happened, the pilots didn't need to hear the clicks to suspect something was wrong. Their seats falling out from under them and their lunch pushing into their esophagus provided all the notice they needed. If that didn't work, I'm sure the 200 screams would have woke the dead. This is not a gradual trim adjustment or course change. It's a last ditch massive response for when the S has already HTF, and all the drinks have already been spilled.

You're seeing the plane's trying to kill you, every time you release the nose up button in the yoke the trim wheel next to you starts spinning again in reverse, for gods sake at least grab the damn wheel to stop it going nose down again. Why not?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 21, 2019, 12:45:36 pm
Yes the technical term for that part of the tail is the elevator but i wanted to stick to generic terms.

In this discussion we better use terms that do not lead to confusion :)

(https://www.grc.nasa.gov/www/k-12/airplane/Images/airplane.jpg)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 21, 2019, 12:51:44 pm
^ Indeed. Those ARE the generic terms. If people don't know them, they better learn them to talk in this thread.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 21, 2019, 02:03:52 pm
Quote
What?!? The whole issue with the engines is that the MAX has too much lift, not too little. MCAS’s job is to nudge the nose back down, not up.
The reason for this is because the MAX will easily enter an unrecoverable stall if you are at a high angle of attack, which would not happen with the previous versions. You would be using a high angle of attack when pulling up from an unexpected dive at low altitude. And you would have to deactivate MCAS to do this. The pilot would be manually flying a plane that handles very differently and stalls much easier than the plane he was certified on. The new plane was slipped under the same certification because of this MCAS system.
Yup, I already knew and fully understood this. Hence why I was like "wtf" at your comment.

You focused on the wrong aspect of the word "lift".  It was not the magnitude of the lift force that was intended in the cited statement, but the aspect of "lift and handle" (perhaps better stated as just "handle") "like a regular 737".

The point being that when thrust is added in the MAX, it has a (significantly) greater upward turn moment than that of earlier models of 737.  This will cause more pitch up than a pilot used to the older models would expect ... ie. it does not handle "like a regular 737".
I understand this. But I didn't "focus on the wrong aspect", actually: at the moment when I actually clicked "Quote", it only said "lift", not "lift and handle" — that was edited in later. (I didn't notice it sneak into the quoted text.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 02:49:53 pm
Quote
Yup, I already knew and fully understood this. Hence why I was like "wtf" at your comment.
This is clear as mud. Not the transparent kind.

I get wordy and confusing, at times. But this pretty much sums up what I meant:

The MAX can't necessarily pull up in a tighter radius or G force than the original 737. Yeah, the moment of inertia from the engine will push the nose up more than the original. But the elevator can do that just fine as much as you would ever need; the engines need not do this at all. It seems evident to me that MCAS is needed because the MAX is not as controllable at this high AOA. Even after you cut the engine back, the aerodynamic lift and drag of the larger, higher, farther forward engines in this high AOA presentation make the plane want to nose up (more).

So I sorta disagree with Brumby and the popular explanation of this in the news. Yeah, the plane wants to nose up during engine acceleration, but MCAS is not going to kick in until there's near stall conditions. It is expected that 100% of pilots will adapt to the way the plane flies and handles without ever activating MCAS. Else Boeing would be even dumber and more brazen than anyone here has even thought to hand out planes they expect pilots to inadvertently stall. No. MCAS is there for the unlikely event a pilot needs to intentionally utilize an extremely high AOA.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 21, 2019, 03:48:53 pm
My piloting experience is only with RC model planes so I'm not going to claim expertise on the matter, but if I were in the cockpit of an airliner and the plane trimmed itself fully nose down and started plunging to earth I can't imagine having a first reaction other than grabbing the trim wheel and cranking it back up. Clinging to it holding the trim within the authority of the elevator to keep the plane in level flight buys as much time as needed to assess the situation. I mean I realize the machine usually knows what it's doing but if the plane is in a steep dive it seems obvious something is wrong.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 21, 2019, 03:57:52 pm
^Agree, this sounds logical. And I hate to take over the thread with my machine gun posts. I'm hating myself.

But as far as we know, this has maybe happened on 3 occasions, and in 2 of them the plane went down. So either these 4 pilots had no common sense, or this is not as simple as it sounds.

Maybe later, we will find out this has happened a hundred times, and only 2 sets of pilots went down the wrong path. Or maybe it really was only the 3 occasions and 4 out of the first 6 pilots (7 if you include the 3rd NP on the plane that properly cut the stab trim) just happened to be out of the norm.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 21, 2019, 04:07:12 pm
At high angle of attack, the plane isn't flying nose first.

Right.  :-DD

I would not have put it this way, but it is essentially correct. I mean, it is always correct in the sense that when the angle of attack is not 0.0, the aircraft is not flying, relative to the wind, in the same direction it's pointing. At high AOA, this is a noticeable difference. Again, this may seem absurd to non-pilots, but this is just how planes are. The direction they are going relative to space, relative to air, and relative to which way they are pointed can all be different, and usual are.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 21, 2019, 04:11:34 pm
Quote
Stall characteristics of MAX is the same as NG. What's different - increased pitch up effect of the LEAP-1B engines, their placement (forward & up). Pitch-up increases AOA which may lead to stall.
But additionally, at high angle of attack, the engines themselves aerodynamically produce lift and drag. At high angle of attack, the plane isn't flying nose first. The vector of travel is at an angle to the attitude of the plane. And larger engines further forward is like an "air brake" giving the effect of the plane wanting to flip/rotate. This is very pronounced. We know this because of the degree of trim movement that MCAS needed to make.

Let's be careful to distinguish between stall characteristics, and the aerodynamics of the airplane at high AOA, but near a stall.

I don't think anyone has discussed stall characteristics of the 737 on this thread. I don't know what they are, and I suspect precious few have experienced them, mostly Boeing test pilots. The whole "system" is built around not getting there.

This whole discussion concerns avoiding getting into stall territory, and from what I've read, MCAS was designed to deal with the fact that as you get near a stall, the airplane starts to push further towards the stall on its own, and this tendency is either not present in the non-MAX versions, or it is weaker.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 21, 2019, 04:16:03 pm
^Agree, this sounds logical. And I hate to take over the thread with my machine gun posts. I'm hating myself.

But as far as we know, this has maybe happened on 3 occasions, and in 2 of them the plane went down. So either these 4 pilots had no common sense, or this is not as simple as it sounds.

Maybe later, we will find out this has happened a hundred times, and only 2 sets of pilots went down the wrong path. Or maybe it really was only the 3 occasions and 4 out of the first 6 pilots (7 if you include the 3rd NP on the plane that properly cut the stab trim) just happened to be out of the norm.

Something else we agree with. I think pilots should have handled this situation pretty readily, and yet they did not. That could be for any number of reasons, and we just don't know what they are yet. But I think that gets to my overarching point which is that the world seems ready to throw Boeing management in prison for pushing an unsafe airplane, and I think the reality is much more complicated. (In fact, I'm surprised at the rush to judgment regarding the very *idea* of this airplane being fundamentally flawed.) We obviously need to find out why the MCAS system "went haywire", but we *also* need to find out why pilots aren't following the emergency procedures they were supposedly trained to follow by memory.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 21, 2019, 04:20:25 pm
^Agree, this sounds logical. And I hate to take over the thread with my machine gun posts. I'm hating myself.

Another way we agree. I am not having any fun in this thread and probably need to step away from the keyboard. :-)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on March 21, 2019, 05:39:58 pm
Disturbing facts ...

Reuters : Ethiopia crash captain did not train on airline's MAX simulator: source (https://www.reuters.com/article/us-ethiopia-airplane-simulator-exclusive/ethiopia-crash-captain-did-not-train-on-airlines-max-simulator-source-idUSKCN1R20WD)

“Boeing did not send manuals on MCAS,”

“Actually we know more about the MCAS system from the media than from Boeing.”

“It is still very disturbing to us that Boeing did not disclose MCAS to the operators and pilots,”
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Marco on March 21, 2019, 06:02:31 pm
Jumpin' Jesus on a pogo stick! They didn't have to turn off the MCAS! They had to turn off the trim system, which of course, they knew about.

The normal failure mode they seem to be trained for is a continuous run away though. The mach system they knew about could not produce such a failure mode AFAICS (though it can be dangerous in its own right on a malfunction at low altitude). Stuck switches or shorts could never produce such a failure mode ... it would be a one in a billion type failure mode without MCAS.

As I said, more a hobble away than a runaway.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 21, 2019, 06:52:13 pm
The normal failure mode they seem to be trained for is a continuous run away though. The mach system they knew about could not produce such a failure mode AFAICS (though it can be dangerous in its own right on a malfunction at low altitude). Stuck switches or shorts could never produce such a failure mode ... it would be a one in a billion type failure mode without MCAS.

You're right. The word "continuous" in the instructions is not exactly consistent with this scenario, and I guess that could have kept pilots from following it. However, though this problem was intermittent, when the trim motor ran, it ran for a rather long time - 10 seconds, and I believe 2.5 degrees of stab movement per go; as I understand it, that's an awful for a 737.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 21, 2019, 07:29:11 pm
The AOA DISAGREE dash LED is optional, Boeing just announced it's making it mandatory. Airbus includes it for free.
I wonder how much it cost, this aviation-spec LED, some wire and a connector. It must be $10,000's of dollars on a $120M aircraft.

Missing a lousy LED on the instrument panel is beyond pathetic  :palm: caught up in politics and marketing.
I have to agree:
"Boeing's 'Optional' Safety Equipment on the 737 Max is a Monument to Corporate Greed" (https://www.esquire.com/news-politics/politics/a26894297/boeing-737-max-optional-safety-equipment-pay-extra)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: imo on March 21, 2019, 07:32:06 pm
https://www.ft.com/content/d726faea-4b36-11e9-bbc9-6917dce3dc62 (https://www.ft.com/content/d726faea-4b36-11e9-bbc9-6917dce3dc62)
Quote
Boeing will install an extra safety alarm in the cockpits of all its 737 Max aircraft after intense criticism in the wake of two fatal crashes.

The US aerospace group has decided to include a warning light in new 737 Max planes and to retrofit all existing ones, according to a person familiar with the situation.

The alarm will tell pilots if two “angle of attack” sensors — which indicate the angle of a plane’s nose — disagree, a sign that one is not working.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 21, 2019, 07:56:14 pm
I mean, it is always correct in the sense that when the angle of attack is not 0.0, the aircraft is not flying, relative to the wind, in the same direction it's pointing.

Right. Boeing does good job explaining AOA:

(http://www.boeing.com/commercial/aeromagazine/aero_12/images/attack_whatisaoa.jpg)

http://www.boeing.com/commercial/aeromagazine/aero_12/attack_story.html
 (http://www.boeing.com/commercial/aeromagazine/aero_12/attack_story.html)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 22, 2019, 01:41:12 am
This new 737 model  was built as and designated as a 737 in order to save certification time and training costs for airlines that were the customers of the planes.

At the end of the day, the 737 MAX should NOT have been a 737. The basic 737 airframe is not compatible with the engine size they needed to put on the plane. and when they did it anyway the airframe became unstable, in that approaching a stall the plane becomes more likely to go into a stall. this is nothing like the behaviour of any 737 in the nearly 50 years 737s have been in the sky.

And now it appears that the massive control system hack put in place to try and neutralise the massive mechanical problem caused by using engines that were too large ended up being "downplayed" so that the 737 certification could stand. "downplayed" to the point that it doesn't even tell you when it's operating! (and massive incompetence in the actual execution of the control system - the active control system only even looks at one vane to make decisions that can kill everyone on board if the vane is faulty!)

Yes in a perfect world a non-panicked pilot is sometimes able to work out what is wrong with a crashing 737 max, because we know  a few did... It seems they are especially able to work it out if they have had training on how this new 737 isn't like every other 737 they ever flew... but in 2 cases now, the pilots didn't... so.... it's kind of obvious that whatever was done was nowhere near enough. Just by the results we have seen in the world.

So all the armchair pilots sitting here saying "but they should have adjusted the trim back" - yeah I'm sure you're a cool and in control genius, and you would have magically worked out what exactly was going on with the whole visual field full of dials and controls while the plane was randomly just pulling your control column away from you and falling out of the sky while you tried to fly it, and saved the day. But so far two flight crews managed to not save the day and hundreds of people are dead. So it seems that unfortunately real commercial pilots aren't as good as you...

This is 100% the result of a corporation using weakened regulatory systems to cut costs at the expense of human lives.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 22, 2019, 03:18:19 am
The AOA DISAGREE dash LED is optional, Boeing just announced it's making it mandatory. Airbus includes it for free.
I wonder how much it cost, this aviation-spec LED, some wire and a connector. It must be $10,000's of dollars on a $120M aircraft.

Missing a lousy LED on the instrument panel is beyond pathetic  :palm: caught up in politics and marketing.
I have to agree:
"Boeing's 'Optional' Safety Equipment on the 737 Max is a Monument to Corporate Greed" (https://www.esquire.com/news-politics/politics/a26894297/boeing-737-max-optional-safety-equipment-pay-extra)
LED?? No. It’s an on-screen indicator on one of the color LCDs, according to a video I saw.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 03:23:36 am
So all the armchair pilots sitting here saying "but they should have adjusted the trim back" - yeah I'm sure you're a cool and in control genius, and you would have magically worked out what exactly was going on with the whole visual field full of dials and controls while the plane was randomly just pulling your control column away from you and falling out of the sky while you tried to fly it, and saved the day. But so far two flight crews managed to not save the day and hundreds of people are dead. So it seems that unfortunately real commercial pilots aren't as good as you...

This is 100% the result of a corporation using weakened regulatory systems to cut costs at the expense of human lives.


But that isn't what it was doing. It didn't "pull the control column" anywhere, it spun the trim wheels fully nose down, an action that is impossible to not notice happening or recognize. When you say "visual field full of dials and controls" it makes it sound like an aircraft instrument panel is a sea of random controls that the crew has no idea what they do, while in reality any competent pilot knows precisely what all of them do and where they all are from memory. A pilot needs to be able to deal with situations like this, whether due to a design fault with the aircraft, a mechanical failure or some external factor. The fact that these crews apparently didn't do that suggests a degree of incompetence. I'm not going to judge them entirely until we have all the details but to assert that this is "100%" anything at this point is quite frankly bullshit, we don't know what happened with certainty yet, but assuming things played out the way early evidence suggests, then the crew gets at least a portion of the blame here. I will remind you that there are at least a couple actual certified pilots in this thread, not just a bunch of armchair goobers who haven't got a clue.

There have been a LOT more incidents throughout aviation history where flight crews not only failed to save the day, but actively caused the accident through their own error or neglect. The fact that two may have failed to deal with the same situation here does not necessarily absolve them from blame.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: blueskull on March 22, 2019, 03:29:28 am
LED?? No. It’s an on-screen indicator on one of the color LCDs, according to a video I saw.

I think the LED on a small "button panel" was a paid option, while the LCD indication icon is what they promise to deliver this time.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Dundarave on March 22, 2019, 04:14:25 am
Is it just me, or does anyone else think that there's something immoral about Boeing designating functionality that is for the sole purpose of increased flight safety (such as the "disagree light") as "optional" and charging extra for it?  And thus allowing corporate airline customers to opt-out of paying for it to be implemented in their aircraft?  Comfort and operational economy options, sure.  But items that can only be classified as "safety-related" and designed to notify when the rest of the aircraft isn't performing up to its paid-for specifications at the potential expense of all the lives aboard?  Apparently, Boeing has a corporate policy which holds that not all passengers deserve equal levels of flight safety.

On each flight, there are, like, 200-odd passengers who assume when they buy their ticket that the aircraft they are flying in is as safe as the aircraft industry can reasonably make it.   Airlines who fly equipment that is not "as safe as the industry can reasonably make it" due to missing safety options that could have been purchased, but were not, should be forced to make that information public.  Letting consumers vote with their feet about what airlines they want to fly based on who's "cheaped out" on their safety is likely the only way to put a stop to what I consider outrageous, money-chiseling, negligent behaviour.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 22, 2019, 05:16:11 am
At the end of the day, the 737 MAX should NOT have been a 737.

Firstly, that statement suggests to me you do not understand the type rating system at all.  I'm not a pilot, but I have been following some of the ecology...

There are many variants of the 737 and just because a pilot has been "type rated" for one model does not mean they can hop into the cockpit of any 737.  Where the changes are significant enough - and these do exist in the 737 line - pilots must go through the full "type rating" process, which impacts both pilots and airlines.  However, there are several models where the differences are minor and a pilot rated for a previous model may only need to undergo "difference training" to be qualified to fly the new version.  This is easy to achieve and represents minimal impact to an airline and their pilots.  This is the reason why any aircraft will not have too many things change, to make sure the differences are small enough so that "difference training" is all that is needed.

There's nothing wrong with the MAX-8 being presented as a 737.  What may be the case (which could be part of the fall-out of these incidents) is that it should have been classed as a new type.  In that case, pilots will need to do type rating - and that is going to impact everyone.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 22, 2019, 05:56:21 am
LED?? No. It’s an on-screen indicator on one of the color LCDs, according to a video I saw.

I thought it is located on the center forward panel?  Air Canada and WestJet had already ordered the aircraft with the indicator light but I don't have pics.

Why would Boeing charge $ for some text annunciator on an LCD?  Putting the word AOA DISAGREE on an LCD. They charge money for that!?!  :wtf:
Southwest Airlines is adding an AoA "indicator" (gauge) on the primary flight display. I'm not sure that is useful- what happens when there is a sensor disagreement, to not create confusion.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 22, 2019, 05:58:48 am

There have been a LOT more incidents throughout aviation history where flight crews not only failed to save the day, but actively caused the accident through their own error or neglect. The fact that two may have failed to deal with the same situation here does not necessarily absolve them from blame.

what happened is we have had two crashes one after the other with new planes of the exact same model, killing hundreds of people.... Even if those two crews weren't the best pilots in the world, I expect that they had managed to not kill everyone while flying plenty of other 737s before. Both crews came unstuck on this new model.

I think it's safe to say that the the differences of this particular plane from any previous ones, and the way those differences were handled, was a massive error of judgement that has cost hundreds of lives.

And when i say "error of judgement" I mean "conspiracy of criminal negligence that should see the people involved in the highest levels of managing the project imprisoned for the rest of their lives, and Boeing out of business if it can't afford to do either a full recall of their not-fit-for-purpose planes. Or at very least, complete some kind of retrospective "new plane" process on this model for all the planes of this type currently out there."

There's a particular concern with the allegation that their software bodge was baked into the system and hidden in a way that it was not obvious it even existed, letalone obvious it was operating.... And the allegation that it only used the mechanical vane sensor on one side of the plane to make string of repeated decisions that ended up killing everyone on board, and didn't even have the ability to cross check the plane's dual sensors for sensor faults.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 22, 2019, 06:08:16 am
There's nothing wrong with the MAX-8 being presented as a 737.  What may be the case (which could be part of the fall-out of these incidents) is that it should have been classed as a new type.  In that case, pilots will need to do type rating - and that is going to impact everyone.

Thanks for the terminology tip.

But it's more than just pilots doing the training to be allowed to fly it.
They should have to prove the that this new type (of which over a hundred planes just like the 2 crashed ones are out there in the world by now) is even fundamentally ok to have pilots trained to operate it.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BravoV on March 22, 2019, 06:16:01 am
All the dirt that had swiped underneath the carpet, are starting to pop out one by one.


CNN : Pilots transitioned to 737 Max 8 with self-administered online course (https://edition.cnn.com/2019/03/22/us/max-8-boeing-self-administered-courses-lion-air-ethiopian-airlines-intl/index.html)

Quotes :

Pilots of Southwest Airlines and American Airlines took courses -- lasting between 56 minutes and three hours -- that highlighted differences between the Max 8 and older 737s, but did not explain the new maneuvering characteristics augmentation system, know as MCAS, the spokesmen said.

"MCAS was installed in the aircraft and Boeing didn't disclose that to the pilots," said Trevino, while adding that Southwest pilots are experienced with 737s.

"This is ridiculous," said Captain Dennis Tajer, a representative of the Allied Pilots Association, which represents 15,000 American Airlines pilots. "If you're going to have equipment on the airplane that we didn't know about, and we're going to be responsible for battling it if it fails, then we need to have hands-on experience."
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: mtdoc on March 22, 2019, 06:32:02 am
The basic 737 airframe is not compatible with the engine size they needed to put on the plane. and when they did it anyway the airframe became unstable, in that approaching a stall the plane becomes more likely to go into a stall. this is nothing like the behaviour of any 737 in the nearly 50 years 737s have been in the sky.

Yes, and if true, this is why the 737 Max will not (or should not) fly again.  All the focus in this thread on armchair piloting and engineering bodges seem to be ignoring this fundamental and overwhelming design flaw. A different or better bodge wil not fix the underlying problem which if the plane is continued to be allowed to fly will eventually result in more deaths. 

But I do not want to underestimate the corporate power, greed and regulatory capture at work here so maybe they will be stupid enough to allow it to fly again after the new bodges are in place.... ::)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 06:40:52 am
There have been a LOT more incidents throughout aviation history where flight crews not only failed to save the day, but actively caused the accident through their own error or neglect. The fact that two may have failed to deal with the same situation here does not necessarily absolve them from blame.

The blame here has already been established: 737M8 and M9 are grounded worldwide. Simple as that.

No it has not been established, and it's not as simple as that. The planes have been grounded until the investigation determines what happened and what if any corrective actions must be taken. There may well be a problem with the aircraft but grounding them by no means establishes blame.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 06:50:59 am
Yes, and if true, this is why the 737 Max will not (or should not) fly again.  All the focus in this thread on armchair piloting and engineering bodges seem to be ignoring this fundamental and overwhelming design flaw. A different or better bodge wil not fix the underlying problem which if the plane is continued to be allowed to fly will eventually result in more deaths. 

But I do not want to underestimate the corporate power, greed and regulatory capture at work here so maybe they will be stupid enough to allow it to fly again after the new bodges are in place.... ::)

It will absolutely fly again, I would wager a substantial amount of money on that fact. It will probably go on to have a good safety record, just as many other planes have in the past. There have been numerous cases of design flaws on new aircraft causing deadly crashes, aircraft type groundings and investigation, and in not one single one of these cases did the type not fly again. Won't happen here either, it's silly to even suggest it as a possibility. These incidents will certainly cost Boeing sales but the problem will be solved and the planes will be back in the air.

Absolute most drastic case, MCAS will be removed and pilots will require re-training to deal with the different handling characteristics of the max. Some people here seem to fail to comprehend this, it is not unstable or badly mannered, it simply handles differently than the 737 classic and thus requires the MCAS in order for it to be flown by pilots certified on the 737 classic. The upward pitch when thrust is increased is a characteristic of ALL airliners with engines slung under the wings. The difference here being the max exhibits this to a greater degree.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 07:04:00 am
Oh yeah, de facto it has been established, on official paper it just takes more time. Otherwise find me other pilot error produced accident in which a global fleet was grounded. Or a pilot induced accident in which the justice department did subpoena Boeing and the FAA, or ....


Unless you know something that the rest of us don't, you don't know whether it was pilot induced, or caused by a flaw in the aircraft, or caused by a combination of these, or something else entirely. It's sensible to ground the aircraft because there is reasonable suspicion of a problem with the design but that is not the same as establishing blame. The investigation is underway, it will be months before blame is established, and it will probably turn out to be a cascade of events that all worked together to cause the accidents.


When a person is suspected of a crime they are arrested and charged, if it is a serious crime they will be detained, but that does not establish blame. They are innocent until proven guilty in a court of law, in other words the court establishes blame, and only after the crime is investigated and the evidence examined. Sadly many people do not understand this and jump the gun trying to be an armchair judge and jury all rolled into one.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 22, 2019, 07:15:18 am

Absolute most drastic case, MCAS will be removed and pilots will require re-training to deal with the different handling characteristics of the max. Some people here seem to fail to comprehend this, it is not unstable or badly mannered, it simply handles differently than the 737 classic and thus requires the MCAS in order for it to be flown by pilots certified on the 737 classic. The upward pitch when thrust is increased is a characteristic of ALL airliners with engines slung under the wings. The difference here being the max exhibits this to a greater degree.

My reading of the fundamental issue that the hidden software bodge was designed to overcome, is the 737 MAX8 not only exhibits regular upward pitch when thrust is increased, but far worse - it also exhibits more upward pitch increase the more the upward pitch is increased.... ie the upward pitch on the 737 MAX8 has a positive feedback element that is not present on other 737s (or pretty much any other commercial plane ever) and the plane is aerodynamically unstable for that reason.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 22, 2019, 07:27:01 am
.... and the plane is aerodynamically unstable for that reason.

How wrong can you be?

IF it WAS aerodynamically unstable, then how come there have been thousands of successful flights?

Such illogical statements don't add to the discussion, but make a mockery of it.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kleinstein on March 22, 2019, 08:09:48 am
.... and the plane is aerodynamically unstable for that reason.

How wrong can you be?

IF it WAS aerodynamically unstable, then how come there have been thousands of successful flights?
......

Most planes get  aerodynamically unstable at to high an AoA - that is what the stall problem is about. The problem with the 737max can be that high high thrust the critical AoA can be lower than normal. So adding thrust can be even worse.

With a working MACS (e.g. no sensor failure) the system seems to work OK and they even got through with only minimal extra training.

I am a little skeptic about the option to only give only better instructions to the pilots on how to disable the MACS. They would ad least need quite some extra (e.g. simulator) training on how to fly with the MACS deactivated.

My guess is Boing will have to update the software and give some training / info to the pilots, so that the system is less likely to fail (e.g. use both sensors, limit the power) and the pilots know better how to handle a possible upset. So it's more like a question on how long the planes stay at ground. If thing go well maybe before the summer season, would be nice to be ready before the winter season.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: blueskull on March 22, 2019, 08:14:23 am
I'm amazed that by now no H1B software programmer from India was blamed for this whole issue, ICE could deport him aaaaand case closed.

If they trust someone to code on a plane, that guy should at least be a senior employee, maybe 3+ years with the company.
And no programmer is going to work for a company on H1B for a few years.

Usually it's OPT->H1B->EB3->Green card.
If I work for a company and I don't see my I140 filed the next year I got H1B, I'll see myself out.

And if someone fits Boeing's requirement, he/she would probably have a PhD from a good university, so why not self petite EB2 NIW?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 22, 2019, 08:51:30 am

How wrong can you be?

IF it WAS aerodynamically unstable, then how come there have been thousands of successful flights?

Such illogical statements don't add to the discussion, but make a mockery of it.

I dunno... how wrong can you be?  It looks like you are trying to make it a competition or something. those 3 sentences have an amazing hit rate for wrongness. I'm not sure I'll be able to keep up but hey, I'll give it a red hot go:

Now. In absence of you going and reading up on control theory or even just feedback in systems I'll break what I said down into smaller steps for you, and try to explain the terminology so you can keep up with the discussion and stop resorting to derailing the discussion and making a mockery of it by acting abusively.

So, what I'm talking about with this new plane, is there's a problematic state variable in a flying plane "system". This state variable is either "pitch" or "angle of attack" (whichever it happens to be, the particular one is unimportant for this discussion.. possibly it's also tied to a second state variable, which I'd expect might be "thrust", maybe there's even more associated variables.. but I'm leaving that out for the sake of simplicity.. only one contains the feedback mechanism when feedback starts, so it's the critical one here)

1) This state variable, for some range of values, has a positive feedback loop. That is - for a range of values of the state variable, with no control operating on that variable, that state variable will increase without bound (well, until hitting a natural limit of the system, stalling the plane, and killing everyone onboard)

2) The positive feedback effect on that state variable is literally a case of instability for that state value. Other 737s in flight do not have this positive feedback on this state variable and therefore this state variable isn't unstable for other 737s in flight.

3) Instability in any one (or more) state variables of a system literally defines that system to be unstable. that's, like, the definition of an unstable system...  Now, other planes that don't have positive feedback in any state variables don't meet this definition. This plane does, though.

4) Now, we need to take a moment and back off from the definition above and realise that a system being "unstable" doesn't necessarily mean the whole system just oscillates chaotically in the full range of all its state variables and is impossible to control in any way from the instant it starts in motion (that would be your worst case for instability in a system)

5) In the case of this plane, instability most likely makes it harder to control the plane when the system hits a state variable value that brings in positive feedback... Which is exactly what the software bodge is there to try and avoid in this plane, but seems it did that in a terrible way. The very existence of this software bodge tells us explicitly that Boeing knew that not only is the flying plane unstable in this variable, it's bad enough that the instability needs to be countered (or masked) You don't bodge software like that up and put it inside a life critical control system just because you're bored on a rainy weekend, you know.


PS, I'm not an expert on aerodymanics  here, but it's my understanding that a lot of fighter planes are deliberately aerodynamically unstable in different ways because it allows them to do fast manoeuvres they couldn't do if they were stable... BUT fighter planes have ejector seats for that reason, and aren't full of passengers for that reason (OK, and probably other reasons...)

Anyway, here's some fun discussion on fighter plane stability I googled for you. Enjoy. But please be very careful not to sign in and abuse the people on this stack exchange about how they are stupid and not contributing to a discussion on fighter plane instability and control, because if fighter planes were unstable how could they ever fly, and thousands of fighter plane flights happen every day.
https://aviation.stackexchange.com/questions/8049/are-fighter-jets-designed-to-be-so-inherently-unstable-that-a-human-cant-fly-on (https://aviation.stackexchange.com/questions/8049/are-fighter-jets-designed-to-be-so-inherently-unstable-that-a-human-cant-fly-on)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 22, 2019, 09:56:31 am
5) In the case of this plane, instability most likely makes it harder to control the plane when the system hits a state variable value that brings in positive feedback... Which is exactly what the software bodge is there to try and avoid in this plane, but seems it did that in a terrible way.

Thank you, well explained. Chain of events for many may seem like: high thrust of engines pitched plane up, MCAS activated and decided to kill everybody by trimming horizontal stabilizers into deadly nosedive. Definitely it was not that simple. Problem could be that positive feedback pitch-up is non-intuitive for pilots that are not trained for such. They may see MCAS actions (trim) as "this f**ing plane does not let me gain altitude as fast as I am used to". If they counteract MCAS trim using other control surfaces - it will make things worse. How else we can explain stabilizer trim jackscrew to be in full nosedive position while plane was gaining altitude & overspeeding till last moments? It may not be faulty AOA instrument. It could be so that pilots were successfully operating older 737 planes closer to critical AOA than treshold is set for MCAS. Suddenly MCAS decided that what they do is not safe, started to trim, pilots did not know what the plane is doing, was trying to compensate using wrong controls/approach. When pilots counteract stabilizer trim during speed increase at high thrust, sooner rather than later trimmed for dive stabilizer will be more effective than all the other controls combined that are in the pilots hands (joystick).

To me it seems like "pilot not trained for particular (type of the) plane", like this airplane crash (https://en.wikipedia.org/wiki/Lokomotiv_Yaroslavl_plane_crash). They were taking off with parking brake activated...
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 22, 2019, 10:07:44 am
of which over a hundred planes just like the 2 crashed ones are out there in the world by now
376 delivered to customers as of last month.

The blame here has already been established: 737M8 and M9 are grounded worldwide. Simple as that.
Such things have happened before. The DC-10 fleet was grounded by the FAA (they even pulled it's type rating) early in its career for a series of accidents. Yet it went on to a successful passenger career. A bunch of them are still flying in cargo service (most are now called MD-10's after a glass cockpit upgrade that allows them to share a type rating with the MD-11). Fex-ed operates most of them.

The 737 classic had rudder failures earlier in its career that caused fatal crashes and control problems. Took them years to figure that one out and years more before they were all retrofited. There were so many in the sky that I don't think anyone even considered grounding the entire fleet. It would have crippled airlines around the world.

And that's just off the top of my head. The other guys are right, the 737-MAX is going to fly again, and probably fairly soon. I'd put money on it.

I dunno... how wrong can you be?  It looks like you are trying to make it a competition or something.
You might be winning this competition.


PS, I'm not an expert on aerodymanics  here
That's real obvious. Yet you're acting like an authority with your conclusions.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 22, 2019, 10:33:23 am
PS, I'm not an expert on aerodymanics  here
That's real obvious. Yet you're acting like an authority with your conclusions.

What he tells about positive feedback is not conclusion, but well known fact:

Quote
The engines were both larger and relocated slightly up and forward from the previous NG CFM56-7 engines to accomodate their larger diameter. This new location and size of the nacelle causes it to produce lift at high AoA; as the nacelle is ahead of the CofG this causes a pitch-up effect which could in turn further increase the AoA and send the aircraft closer towards the stall.

All this adds to pitch-up effect from engine thrust.

http://www.b737.org.uk/mcas.htm (http://www.b737.org.uk/mcas.htm)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 22, 2019, 10:57:44 am
PS, I'm not an expert on aerodymanics  here
That's real obvious. Yet you're acting like an authority with your conclusions.

What he tells about positive feedback is not conclusion, but well known fact:

Quote
The engines were both larger and relocated slightly up and forward from the previous NG CFM56-7 engines to accomodate their larger diameter. This new location and size of the nacelle causes it to produce lift at high AoA; as the nacelle is ahead of the CofG this causes a pitch-up effect which could in turn further increase the AoA and send the aircraft closer towards the stall.

All this adds to pitch-up effect from engine thrust.

http://www.b737.org.uk/mcas.htm (http://www.b737.org.uk/mcas.htm)

This is not a software analysis that's simulated to guaranteed failure in 0.01 seconds. There's real physics and time and pilot opportunities to correct involved. What an automatic system can do automatically, a pilot can do manually, if necessary. In any case, the engine placement is NOT the direct cause of these accidents. Focus on what actually went wrong.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 22, 2019, 11:14:23 am
This is not a software analysis that's simulated to guaranteed failure in 0.01 seconds. There's real physics and time and pilot opportunities to correct involved. What an automatic system can do automatically, a pilot can do manually, if necessary. In any case, the engine placement is NOT the direct cause of these accidents. Focus on what actually went wrong.

Even Boeing admitted that most likely source of crash is (possibly inferior) MCAS system which were introduced for which exactly reason? - Engine placement. So, please, don't.... Also you have no authority to tell what we shall focus on or not. On the other hand I agree to you that most likely they will solve potential issues w/o scrapping MAX or reverting it to NG engines.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 22, 2019, 12:04:02 pm
My reading of the fundamental issue that the hidden software bodge was designed to overcome, is the 737 MAX8 not only exhibits regular upward pitch when thrust is increased, but far worse - it also exhibits more upward pitch increase the more the upward pitch is increased.... ie the upward pitch on the 737 MAX8 has a positive feedback element that is not present on other 737s (or pretty much any other commercial plane ever) and the plane is aerodynamically unstable for that reason.
The thing is, having an inherently aerodynamically unstable airframe and using software to make it what I'll call "apparently stable" to the pilots is a completely valid design approach. (Think of the Segway scooter, which is only possible because of software.)

So, operating under the assumption that MCAS is what failed, my take on this is that Boeing screwed the pooch in the implementation of MCAS.

1. It should not have been allowed to make such drastic corrections. The maximum correction per intervention event is already far more than they'd originally planned — and had submitted to the FAA — but the real issue is that if a pilot overrides a full-scale MCAS intervention, even by the tiniest amount, MCAS will re-trigger soon and can apply full-scale correction again, resulting in MCAS being able to push the elevators all the way nose-down. This is many, many, many times more correction than it had been described as being capable of, and I'm fairly confident this was not by design. (It should only be able to apply a certain amount of total cumulative correction, rather than only being limited within a single intervention, but unlimited in the number of interventions it can make.)

2. The other issue, arguably the bigger one, is that MCAS seems to use only the input from a single AOA sensor, which is insanity IMHO, especially given that the plane already has more than one such sensor! I can't imagine any reason why you wouldn't use the inputs from hardware that's already in place. IIRC, the MAX has two AOA sensors, which of course means that in the case of disagreement, you can't immediately know which one is wrong. So I totally agree with the others who've said that simply, there should be three, so that you can do a "best 2 of 3" analysis and thus have a reading with a high level of confidence.

Both of these flaws have to be in place at the same time for the crashes to happen in the way we suspect as of right now. Fixing either one would have prevented the crashes. And both are comparatively easy to fix, so if I were Boeing, I'd fix both.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 22, 2019, 12:12:34 pm
As I said before, I am not sure this plane will fly again with the same name.
It has a bad reputation and people don't want to fly in it anymore.

Today the first airliner cancelled their order of 49 MAX planes .
Sorry only dutch but translated: the reason for the cancelation is that their customers have lost all trust in this plane and the airliner would like to order a different type of plane.

https://www.nu.nl/economie/5804268/vliegmaatschappij-garuda-indonesia-annuleert-bestelling-49-boeings.html (https://www.nu.nl/economie/5804268/vliegmaatschappij-garuda-indonesia-annuleert-bestelling-49-boeings.html)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 22, 2019, 12:19:56 pm
As I said before, I am not sure this plane will fly again with the same name.
It has a bad reputation and people don't want to fly in it anymore.
You've said it before, and I'll say again that there's a zero percent chance this will happen.

The DC10, for example, had some design flaws that caused a few crashes early on. It had a similar image problem. But the flaws were identified and fixed, and the DC10 went on to become one of the most successful airliners of its era. Consumers absolutely did not dwell on its early reputation.

The fact is, most people don't even give a second's thought to what aircraft type they're flying on. They assume (correctly) that the airlines have a vested interest in not having their planes crash, and thus that they're airworthy.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 22, 2019, 12:44:24 pm

That's real obvious. Yet you're acting like an authority with your conclusions.

Most of the conclusions I'm talking about are already discussed by people who do have expertise..

I'm not the person who invented the idea that the basic 737 shape is incompatible with the huge engines they bolted on to the max8, and that the hacking on of engines that are too big caused the plane to become unstable.

I'm not the one who first explained how the way this particular plane was allowed into the market and the skies seems to be shady as all hell due to the above 2 points and the apparently secret/hidden fix that was bolted into the plane's software system to try and patch it but apparently spoken about very little.

that post I made that you quoted half a line of out of context was just dealing with someone who wanted to have a go about things and didn't even know the fundamentals of system stability.

my main point in this thread is dealing with armchair pilots who think that despite ALL WE HEAR about how irregular this project was, and how different the plane physically is compared to the 737 version it's pretending to be the same as, that just because one pilot is known to have been able to save one of these planes with the fault from crashing once, that it must mean that the other 2 flight crews whose planes crashed, killing everyone on board, must have just been incompetent and the planes are fine.

Maybe they will fly these planes again, because sure, rich people hate losing money, and I bet there's a bunch of rich people directing lackeys right now to make sure they lose the least money possible over this... And sure, maybe it is just going to be a control system update...

Whatever they do, I just want a serious investigation into the suitability of whatever their final fixed version of the plane is, because the first declaration of suitability for that plane was an absolute pile of bullshit. So more of the same process is not going to cut it..  And really, moving forward, airplane manufacturers should not be self-certifying planes if stuff like this can happen.

And hopefully they'll also come to the conclusion that's its a very new and specific type of plane so people get trained properly on how not to die while flying it...

The only conclusion of my own that I've brought up here, really, is that it is looking a bit like this project contained a high level conspiracy to avoid corporate responsibility and save money, at the cost of human safety and now lives... So a thorough investigation into the decisions made by the key high-level people responsible for this project should to be a big priority, and if found to be a criminal conspiracy or even the slightest hit of unethical behaviour, they should be going to prison for consecutive life sentences for each person that died on those planes.. And I'll argue that all day, given what we've heard about the way the project certification was managed, the way new plane introduction and training was managed, and how different this plane apparently is to the plane it's certified to be..
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: julianhigginson on March 22, 2019, 12:55:29 pm
he thing is, having an inherently aerodynamically unstable airframe and using software to make it what I'll call "apparently stable" to the pilots is a completely valid design approach. (Think of the Segway scooter, which is only possible because of software.)


I absolutely agree... some forms of instability can definitely be patched with control systems, and the segway is a great example.... I would never claim otherwise.. but if you're going to do that, the system has to be fit for purpose...

And when we are talking about a plane where a critical error kills everyone on board, that system has to be robust and it has to be incapable of killing people no matter what you throw at it.

And when you're talking about a massive complex thing like a plane where pilots have to be able to override the system if it's going wrong, well you also have to be frank and open about what the plane is, how it actually works, and how it might be different from other planes you've ttold people it's the same thing as..

Quote
Both of these flaws have to be in place at the same time for the crashes to happen in the way we suspect as of right now. Fixing either one would have prevented the crashes. And both are comparatively easy to fix, so if I were Boeing, I'd fix both.

you'd also have to fix the documentation and the training and probably the plane type, but yes I agree, if the MCAS could be made to not fall down in a screaming heap and kill everyone on board, it could possibly be a suitable fix for the planes physical instability, as long as people piloting the plane were fully aware of what it was doing, why it was there, and had some experience flying the plane without it enabled.

Also, whoever let the plane design out with such obvious holes  in the design needs to be seriously investigated (like, did anyone even consider a basic system level FMEA on this thing? that should have pointed out the issue with only one mechanical vane sensor being used as bright as day!)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 22, 2019, 03:56:56 pm
As I said before, I am not sure this plane will fly again with the same name.
It has a bad reputation and people don't want to fly in it anymore.
You've said it before, and I'll say again that there's a zero percent chance this will happen.

The DC10, for example,

Lets continue over a year and we will see.
Referring to planes of the 70s makes no sense, society has changed too much esp social media, internet....
If airliners are cancelling orders it looks bad, I can't say I can blame them.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 22, 2019, 05:06:11 pm
It wouldn't be the first time the sensor is ok but the sensor data that arrives to the flight computer isn't, due a software bug somewhere else.

https://en.wikipedia.org/wiki/Qantas_Flight_72#Final_report (https://en.wikipedia.org/wiki/Qantas_Flight_72#Final_report)
Quote
At 12:42:27 the aircraft made a sudden uncommanded pitch down manoeuvre, recording −0.8 g, reaching 8.4 degrees pitch down and rapidly descending 650 feet (200 m) in about 20 seconds before the pilots were able to return the aircraft to the assigned cruise flight level. At 12:45:08 the aircraft then made a second uncommanded manoeuvre of similar nature, this time reaching +0.2 g, 3.5 degrees pitch down and descending 400 feet (120 m) in about 16 seconds before being returned to level flight.[14][15] Unrestrained passengers and crew as well as some restrained passengers were flung around the cabin or crushed by overhead luggage as well as crashing with overhead compartments. The pilots stabilised the plane and declared a state of alert (pan-pan), which was later updated to mayday when the extent of injuries was relayed to the flight crew
[...]
Final report
Analysis
After detailed forensic analysis of the FDR data, the flight control primary computer (FCPC) software and the air data inertial reference unit (ADIRU), it was determined that the CPU of the ADIRU corrupted the angle of attack (AOA) data. The exact nature was that the ADIRU CPU erroneously relabelled the altitude data word so that the binary data that represented 37,012 (the altitude at the time of the incident) would represent an angle of attack of 50.625 degrees. The FCPC then processed the erroneously high AOA data, triggering the high-AOA protection mode, which sent a command to the electrical flight control system (EFCS) to pitch the nose down

https://www.youtube.com/watch?v=2cSh_Wo_mcY (https://www.youtube.com/watch?v=2cSh_Wo_mcY)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 22, 2019, 05:37:33 pm
well this is getting interesting
so AOA indicators is an option?
like a software addon in oscilloscopes?  :-DD
but they are still suppose to tell the pilot there is a stall? or it did not?

The Wright brothers had (only) an AoA sensor and gauge indicator on their 1903 Flyer. It was a piece of yarn tethered on a stick.
I'm glad Boeing remembers it's kind of important, since day one.

"[Boeing] announced it would now make standard an indicator light that warns pilots of a sensor malfunction"
"A U.S. airline source said that feature would cost roughly $80,000 extra"  :palm:
https://www.cbsnews.com/news/boeing-737-max-plane-crash-company-to-make-standard-light-warning-pilots-of-sensor-malfunction/ (https://www.cbsnews.com/news/boeing-737-max-plane-crash-company-to-make-standard-light-warning-pilots-of-sensor-malfunction/)

edit: added cost
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 05:38:51 pm
And no programmer is going to work for a company on H1B for a few years.

Usually it's OPT->H1B->EB3->Green card.
If I work for a company and I don't see my I140 filed the next year I got H1B, I'll see myself out.

It happens all the time. At a previous job I had we had several developers on H1B visas for years. I'm not a fan of that system but it's not a rare situation.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 06:02:47 pm
Lets continue over a year and we will see.
Referring to planes of the 70s makes no sense, society has changed too much esp social media, internet....
If airliners are cancelling orders it looks bad, I can't say I can blame them.

Irrational behavior has become more common it seems, but I'm still quite confident the max will fly again. All new aircraft have teething problems, and occasionally this leads to disaster. When the Dreamliner battery fires were happening I saw a lot of people say that was the end of the line for those and people wouldn't fly on them yet here we are.

Once the problem has been fixed and the planes are sufficiently tested I would not hesitate to fly on a 737 max. Looking at it rationally, even if nothing were fixed and we just started flying the planes again, I'm still much more likely to die while driving to the airport in a car than in a plane crash from a statistical standpoint. Just to put this into perspective, approximately 50,000 people are killed each year in car accidents in the USA alone. That's approximately a 737 crash every single day of the year in deaths, yet people think nothing of getting into a car.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 22, 2019, 06:11:11 pm
The only conclusion of my own that I've brought up here, really, is that it is looking a bit like this project contained a high level conspiracy to avoid corporate responsibility and save money, at the cost of human safety and now lives... So a thorough investigation into the decisions made by the key high-level people responsible for this project should to be a big priority, and if found to be a criminal conspiracy or even the slightest hit of unethical behaviour, they should be going to prison for consecutive life sentences for each person that died on those planes.. And I'll argue that all day, given what we've heard about the way the project certification was managed, the way new plane introduction and training was managed, and how different this plane apparently is to the plane it's certified to be..

This is a whopper of a conclusion. Though I agree there should be an investigation, and that if there criminal conspiracy or negligence are discovered, there should be punishment, neither of those things are established yet, not even close.

- is the idea of putting large engines on a 737 fundamentally flawed?
- is this airplane significantly different from other 737 that it should have required a type rating?
- if this plane pitches up more at already high AOA's, does that make it fundamentally unsafe?
- is the MCAS concept fundamentally flawed?
- is the MCAS system engineered poorly?
- should it be required for two AOA sensors to agree to activate MCAS?
- did Boeing know (or suspect) that the concept (or implementation) was flawed?
- did Boeing, or people at Boeing, know the airplane was unsafe? Did management override them?
- did Boeing hide information from the FAA? Did they use political power to force the FAA's hand?

NONE of these things are known right now, and they all matter. People seem to think they know the answers to these, but they do not, not even aviation experts.

My contention on this thread all along has been that aviation accident chains are long and complex, and that just because the plane is flawed or broken in some way does not mean the pilots acted competently. I think there's good evidence (not proof) already that the pilots involved did not perform in an exemplary fashion. Was their performance within the expected bounds for pilot capability? That will be another question for investigators to determine, too.

However, that, too is a separate question, and is distinct from everything that might be bad about the airplane, process, or organization that created it.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 22, 2019, 06:45:36 pm
FBI have joined a criminal investigation into the 737 max. certifications.
Boeing essentially putting a "CE" sticker on their planes- they do not have the integrity to do self-certification.

We can keep haggling over the MCAS implementation but, as with many disasters, engineers were steamrollered into deploying something as quickly as possible and thus unsafe.
I think the profession has a huge problem- whistle blow and get fired, or join the corporate group think, keep your job and proceed with corrupt management's instructions.

I see it happening more with other scandals such as Volkswagen emissions , FIU bridge collapse, Theranos, Takata air bags etc.
The executives drive the company hard to maximize shareholder's profits as fast a possible, the result is unsafe products, and all the while the engineer's little voice is ignored.

We're somehow expected as PE's to act only with integrity despite our higher ups overruling that. Boeing surely had engineers that knew this MCAS rollout is shit, Arduino-crowd kind of software quality and bypassing necessary safety design and evaluations. But dare speak up about it and get thrown under the bus.

I'm not sure when or how corporate greed is going to get moderated, how many lives must be lost. Boeing took it to a new level but I can't see anything fixing this.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rdl on March 22, 2019, 07:02:48 pm
Post by Ralph Nader, who apparently lost a relative in one of the crashes.

Greedy Boeing’s Avoidable Design and Software Time Bombs (https://nader.org/2019/03/21/greedy-boeings-avoidable-design-and-software-time-bombs/)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 22, 2019, 08:18:20 pm
Boeing: you third world airlines just need to hire armchair pilots to fly these planes. Every armchair pilot would have cut the stab trim, and they would not have wanted to know what MCAS did or why it was needed, esp whenever they made high AOA maneuvers, thereafter, for whatever reason.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 22, 2019, 08:26:54 pm
Boeing: you third world airlines just need to hire armchair pilots to fly these planes. Every armchair pilot would have cut the stab trim, and they would not have wanted to know what MCAS did or why it was needed, esp whenever they made high AOA maneuvers, thereafter, for whatever reason.

I'll promise not to fly any airliners if you'll promise to stay off accident investigations.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 22, 2019, 08:36:41 pm
Quote
https://www.youtube.com/watch?v=cQirIH_DuAs

You take it too personally, Djacobow.

Serious question: What it takes seconds for an MCAS malfunction to do, how long does it take to undo that after you cut the stab trim? After you cut the stab trim you can't just press the up button on the yoke anymore, right? You have cut all powered control over the jack screw and the horizontal stabilizer. It looks like you'd be turning the wheel for a long time.

As for pilot reaction: If you are used to hearing this thing clacking away during autopilot trim adjustments, then you might not notice it, at all? During AF447, the audio stall warning went off 70 times for over 2 minutes, and the black box recordings suggest that the pilots never even discussed a stall. Some studies have suggested that audio warnings don't register to the pilot under many circumstances, which is why most of the important alerts are not audio, only.

So, when the MCAS goes haywire, the pilots immediate reaction might be nothing. Then after awhile, they might have either tuned out the trim wheel adjusting altogether. Or they might realize, "hey, that trim adjustment has been going on for longer than usual." They might then first wonder why autopilot is turned on when they are sure it is off. Then they might turn off the autopilot (redundantly). Say for sake of speculation that the MCAS just happened to finish doing its thing at the time the pilot pushes the autopilot disengage button. Then he pushes the manual trim button, to get the trim back up. And it works as he expects. Problem solved... but not yet. It happens again. And pilot is on the wrong road from here on out.

Turning ON autopilot would have disabled MCAS. But it might have looked like the autopilot was malfunctioning. Simply knowing MCAS existed could make a huge difference in response.

One of your primary algorithms when flying this plane might be that if instruments are malfunctioning, you can always turn off the autopilot and fly, manually. When you think the autopilot is turning itself on/off and malfunctioning, then you might get some panic and tunnel vision, because your major "out" and feeling of control and safety has been removed. Now your tunnel vision has you locked on the autopilot disengage button, because hitting it seemed to have worked the first time, and now you think the autopilot is trying to kill you. It's obviously not a runaway trim, because it seems to have something to do with the autopilot, and it is not continous. When you press the trim up, it works. When you press trim down, that works. Trim controls are working. Training was maybe very specific under what condition you cut the stab trim, and in the moment the pilot is probably reverting to training and not able to think so clearly due to being so close to death at a fairly low altitude. He's not able to reason that cutting stab trim will prevent autopilot from using it, too (or MCAS, secret autopilot that is the "manual" autopilot).  He is following his checklist.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: djacobow on March 22, 2019, 09:16:59 pm
You take it too personally, Djacobow.

:-)

Serious question: What it takes seconds for an MCAS malfunction to do, how long does it take to undo that after you cut the stab trim? After you cut the stab trim you can't just press the up button on the yoke anymore, right? You have cut all powered control over the jack screw and the horizontal stabilizer. It looks like you'd be turning the wheel for a long time.

Yes, a reasonably long time. I'm a bit surprised that nobody has uploaded a YT video that shows how long it takes to move the trim 2.5 degrees. The wheel spins fast under trim control and just by grabbing the wheel you probably can't even go 1/3 as fast. However, the wheel has a flip-out knob, that you can grab to crank it much faster. I guess it goes as fast as you'd want. My guess is that it would take roughly 2x as long as the trim motors when you're using the knob.

As for pilot reaction: If you are used to hearing this thing clacking away during autopilot trim adjustments, then you might not notice it, at all? During AF447, the audio stall warning went off 70 times for over 2 minutes, and the black box recordings suggest that the pilots never even discussed a stall. Some studies have suggested that audio warnings don't register to the pilot under many circumstances, which is why most of the important alerts are not audio, only.

Fair point. I think it's true that people focus on one thing to the exclusion of others, and this is a known problem in aviation. I didn't know the thing about sound in particular. Information saturation and other sorts of "data absorption" problems have been studied a fair bit in the context of instrument flying: instrument fixation, instrument omission, etc. There's also a lot of work around how long it takes a pilot to work out which instrument has failed. This is something you practice when instrument training, but under pressure, in hard IMC, with a debilitated airplane is a lot different, it has definitely proven fatally difficult.

I had not heard much about people tuning out klaxons, bells, and audio in particular, but to a first approximation, I'd think I'd almost have to tune them out in order to think.

AF447 makes an interesting comparison. The pilot flying may not have known he was stalling because he might not have thought it was possible. Normally, the Airbus provides envelope protection, which means you can yank back on the control stick and the plane will climb at the highest rate it can do so safely. However, because of the pitot fault there was no air data and the computer punted to alternate law without envelope protection. There would have been a screen indication, but who knows if the pilot would have understood it.

AF447, though, is also an example where a pilot could have flown this airplane out of the situation. "All" the pilots needed to do was fall back to early training, attitude flying: pitch + power = performance.

But I also understand why this would have exceedingly difficult: one moment you're monitoring a plane cruising on autopilot, the next moment you are hand-flying a plane not just manually, but one without air data and without the normal FBW characteristics of the A320. I can only imagine it's a jarring and difficult transition.

To my gut, I think I'd rather have the MCAS situation,, but I'm not sure it's productive to compare totally different incidents in totally different airplanes.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: thm_w on March 22, 2019, 09:44:25 pm
Is it just me, or does anyone else think that there's something immoral about Boeing designating functionality that is for the sole purpose of increased flight safety (such as the "disagree light") as "optional" and charging extra for it?  And thus allowing corporate airline customers to opt-out of paying for it to be implemented in their aircraft?  Comfort and operational economy options, sure.  But items that can only be classified as "safety-related" and designed to notify when the rest of the aircraft isn't performing up to its paid-for specifications at the potential expense of all the lives aboard?  Apparently, Boeing has a corporate policy which holds that not all passengers deserve equal levels of flight safety.

Automatic braking systems and lane assist are options on cars that are purely for safety. It costs money to implement these things, someone has to pay for it.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: ogden on March 22, 2019, 10:14:23 pm
Video explaining and possibly answering questions regarding horizontal trim and MCAS:

https://www.youtube.com/watch?v=xixM_cwSLcQ (https://www.youtube.com/watch?v=xixM_cwSLcQ)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 10:40:37 pm
Post by Ralph Nader, who apparently lost a relative in one of the crashes.

Greedy Boeing’s Avoidable Design and Software Time Bombs (https://nader.org/2019/03/21/greedy-boeings-avoidable-design-and-software-time-bombs/)

That's Ralph Nader though, he made a career of criticizing products, greatly exaggerating their flaws. The most famous probably being the Chevy Corvair which was a surprisingly innovative car years ahead of its time. It had some unusual handling characteristics but it was not inherently dangerous for what it was, a car designed to be affordable and fuel efficient with the technology available at the time.

https://www.youtube.com/watch?v=NI9Hq0_Mhy0 (https://www.youtube.com/watch?v=NI9Hq0_Mhy0)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 10:51:14 pm
Is it just me, or does anyone else think that there's something immoral about Boeing designating functionality that is for the sole purpose of increased flight safety (such as the "disagree light") as "optional" and charging extra for it?  And thus allowing corporate airline customers to opt-out of paying for it to be implemented in their aircraft?  Comfort and operational economy options, sure.  But items that can only be classified as "safety-related" and designed to notify when the rest of the aircraft isn't performing up to its paid-for specifications at the potential expense of all the lives aboard?  Apparently, Boeing has a corporate policy which holds that not all passengers deserve equal levels of flight safety.

Automatic braking systems and lane assist are options on cars that are purely for safety. It costs money to implement these things, someone has to pay for it.


I can see both sides here, however in the case of the sensor disagree warning it sounds as if it's purely a software change. Now charging additional money to unlock a software feature is nothing new but I can see the argument over it being a safety feature that should be included standard rather than charging extra.

Automatic braking and lane departure systems require additional hardware that must be included in the car and they're less necessary IMHO than something intended to monitor for fault conditions. A person who pays attention when they drive doesn't need automatic braking or lane departure warnings, but it would be silly for a car manufacture to charge extra money for the brake system failure indicator.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 22, 2019, 11:07:19 pm
You can charge for ABS because the DOT says it is legal to sell and drive cars without ABS. At one point cars didn't require a chest belt in the rear seat or air bags up front.

Just like the FAA cleared the MAX plane as fine without the AOA disagree warning.

I don't think the disagree light is the problem, though. Nor a display. Prior to the MAX, the AOA on a 737 was only ever used to activate a stick shaker. So a malfunction might have erroneously made the stick shake and nothing more? And these two crashes were not stalls.

Nondisclosure of MCAS is a problem. MCAS able to erroneously retrigger without any absolute limit is a problem.

Lack of ability to turn off MCAS is another problem. Stab trim cutout to kill MCAS is like cutting off your arm to spite your hand.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 22, 2019, 11:19:36 pm
I think the reasoning behind not having a separate way of disabling MCAS is that without it the plane does not handle the same as other variants of the 737 and the system is intended to be transparent and effectively part of the trim system. I don't know that having to shut off power to the trim system is too unreasonable in that context which assumes that MCAS is going to behave sensibly. I mean in an Airbus plane you can't shut off envelope protection entirely, the automated systems are considered integral to the flight controls. Quite a few military fighter aircraft are inherently unstable and would drop out of the sky without the automated control systems so you can't shut those off either.

If it turns out that the MCAS system is responsible for these crashes I think the sensible thing to do is redesign it so that it cannot trim down to such an extreme that the pilot cannot override the pitch down trim with up elevator and then come up with a way to make it far more failsafe. I'm fairly confident that a solution can be engineered that will solve whatever problem exists. Boeing knows that they have one shot at this and another related crash after the design is corrected will have a far greater impact.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 22, 2019, 11:50:21 pm
Quote
I don't know that having to shut off power to the trim system is too unreasonable in that context which assumes that MCAS is going to behave sensibly. I mean in an Airbus plane you can't shut off envelope protection entirely, the automated systems are considered integral to the flight controls.

The pilot might not be able to turn off certain protections on the Airbus. But these systems will turn off, automatically, if vital sensors fail, else they might contribute to a problem due to erroneous information. The MCAS doesn't automatically shutoff, even if you had purchased this AOA disagree alert upgrade. It just means you have to see it and then shut off your trim control and break out the crank handle, lol. Since at the time of the first crash, Boeing didn't even tell anyone about MCAS, an AOA failure alert would not have even resulted in any response. "Oh the AOA's don't agree. I'll stop relying on my AOA readings, is all. I never looked at that, anyway. Carry on." They wouldn't have cut the power to trim control to preempt a faulty MCAS response, because MCAS wouldn't even have been in their vocabulary.

Engineering standpoint: it seems barbaric the way MCAS works to begin with. How or why a 2.5 degree stabilizer response would ALWAYS be appropriate seems insanely crude. Matter not where the stabilizer started at, nor what the pilots may have already begun doing with the elevators, nor what the pilot has perhaps started doing with the elevators after MCAS started its one, crude, barbaric, quantum response. What if the AOA changes and says the AOA is normal and/or at least on the way down (due to faulty sensor or wind turbulence or whatnot.. or because the pilot had already applied full down elevators before reaching the AOA limit where MCAS kicked in)? Does the thing just continue cranking to 2.5 degrees down, anyway, and as soon as it's done it is ready for the next triggering? I mean, damn, the way it is described, I could write that software. Anyone could whip that up in an afternoon. And I think most engineers would see why it could be a problem.

Also it seems insane that MCAS makes this permanent and huge change to prevent the stall. Then it just leaves the stabilizer there. And Boeing doesn't think anyone needs to know. If the pilot had approached the stall because he accidentally turned the trim up by 2.5 degrees, unwittingly, and then didn't notice that the MCAS turned it back down to about "normal," then yeah, that would be a great behind-the-scenes response that the pilots need not be aware of. I mean, if the pilot inadvertently pressed the trim up button for 10 seconds and then immediately went unconscious for the the next minute, that would be perfect. In 99% of proper activation, this wouldn't be the case. And I bet the MAX with 2.5 degree nose down trim and no longer in a stall is going to handle a little differently than a normal 737. I suppose the pilot should be automatically executing the grab-the-wheel, cut the stab trim routine the instant it starts... since he is unaware it is supposed to happen. Then fix the plane from stalling, manually.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rdl on March 23, 2019, 01:54:52 am
Doomed Boeing planes lacked two optional safety features (https://www.theguardian.com/business/2019/mar/21/doomed-boeing-737-air-max-planes-ethiopia-indonesia-crashes-lacked-two-optional-safety-features-report)

Safety feature.
Optional.
Extra cost.
 :palm:

Quote
“They’re critical, and cost almost nothing for the airlines to install,” Bjorn Fehrm, an analyst at the aviation consultancy Leeham, told the newspaper. “Boeing charges for them because it can. But they’re vital for safety.”

I bet there are people at Boeing who now wish they had made both standard equipment.



Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Dundarave on March 23, 2019, 02:22:59 am

That's Ralph Nader though, he made a career of criticizing products, greatly exaggerating their flaws. The most famous probably being the Chevy Corvair which was a surprisingly innovative car years ahead of its time. It had some unusual handling characteristics but it was not inherently dangerous for what it was, a car designed to be affordable and fuel efficient with the technology available at the time.


And as a result of "greatly exaggerating their flaws", Ralph Nader was instrumental in the introduction of mandatory seatbelts in the US and Canada, as well as the introduction of collapsible steering wheels (among other influential changes), both innovations resulting in saving the lives of many thousands of people.  Unsafe At Any Speed was the book that started his "career of criticizing products".

<incorrect quote attribution corrected - apologies.>
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: rdl on March 23, 2019, 03:26:28 am
That's Ralph Nader though, he made a career of criticizing products, greatly exaggerating their flaws.
...

And as a result of "greatly exaggerating their flaws", Ralph Nader was instrumental in the introduction of mandatory seatbelts in the US and Canada...

Well, I'm not the one who said that, but it's no big deal.

I did already know who Ralph Nader is. I had a Corvair as a daily driver for a while back in the late seventies. It was fine until a wheel fell off.

If you go to his site to read his comments about "Greedy Boeing", the post "Letter to the FCC Commissioners" is also pretty good.

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 23, 2019, 09:09:17 am
yet people think nothing of getting into a car.
Oh there we go again comparing anything to cars  :palm:
If you do want to compare it you should look at only those accidents with:
- a professional driver
- no alcohol involved
- no other cars or other vehicles/pedestrians involved
- no corners or bad roads, not within city limits (a straight highway without other traffic)
- no speeding or other traffic violations like crossing red lights etc.

If you look at all this the chance of a passenger surviving such an accident with all the safety precautions like airbags, belts, crackle zones is way higher than any passenger in a plane accident.
( please put your head between your legs and brace for impact and oh yeah we put the chairs so close to eachother anyone taller than 1m85 will probably hit the seat in front of him first, nice knowing you). Individual Passenger safety in a plane is the same as in the 50s , it has even been made worse by stuffing more and more people per square meter in that flying can.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 23, 2019, 09:24:09 am
the Chevy Corvair which was a surprisingly innovative car years ahead of its time.

Nothing in the Corvair was "surprisingly innovative" or ahead of its time. No thing at all. It was just an exercise of cost cutting by bolting down together the worst of the worse to make it cheap, as cheap and bad as a Renault 8 in the 60's or a Dauphine (its predecessor) in the 50's. The only time I've seen on the road with my own eyes a car rolling over for no reason, it was an R8. There's nothing worse when cornering than that swing axle suspension https://en.wikipedia.org/wiki/Renault_Dauphine#Technical

Quote
The rear swing axle design, unless ameliorated by any of several options, can allow rear tires to undergo large camber changes during fast cornering, leading to oversteer – a dynamically unstable condition in which a vehicle can lose control and spin. Renault relied on a front anti-roll bar as well as tire pressure differential to eliminate oversteer characteristics – low front and high rear tire pressure — and induce understeer. The tire pressure differential strategy offered the disadvantage that owners and mechanics could inadvertently but easily re-introduce oversteer characteristics by over-inflating the front tires. In the United States, drivers (and General Motors) experienced virtually the same issues with the Chevrolet Corvair. In 1960 Renault revised the suspension with the addition of extra rubber springs up front and auxiliary air spring units (mounted inboard of the conventional coils) at the rear – marketing the system as Aerostable[18] – and giving the rear wheels a small degree of negative camber and increased cornering grip
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 23, 2019, 03:49:27 pm
So, operating under the assumption that MCAS is what failed, my take on this is that Boeing screwed the pooch in the implementation of MCAS.


he thing is, having an inherently aerodynamically unstable airframe and using software to make it what I'll call "apparently stable" to the pilots is a completely valid design approach. (Think of the Segway scooter, which is only possible because of software.)


I absolutely agree... some forms of instability can definitely be patched with control systems, and the segway is a great example.... I would never claim otherwise.. but if you're going to do that, the system has to be fit for purpose...

And when we are talking about a plane where a critical error kills everyone on board, that system has to be robust and it has to be incapable of killing people no matter what you throw at it.
Yes. I think I kinda alluded to all of that in the sentence that followed the quote, namely "So, operating under the assumption that MCAS is what failed, my take on this is that Boeing screwed the pooch in the implementation of MCAS."




And when you're talking about a massive complex thing like a plane where pilots have to be able to override the system if it's going wrong, well you also have to be frank and open about what the plane is, how it actually works, and how it might be different from other planes you've ttold people it's the same thing as..
Yep. I was only talking about the equipment deficiencies, not the training and processes.


Quote
Both of these flaws have to be in place at the same time for the crashes to happen in the way we suspect as of right now. Fixing either one would have prevented the crashes. And both are comparatively easy to fix, so if I were Boeing, I'd fix both.

you'd also have to fix the documentation and the training and probably the plane type, but yes I agree, if the MCAS could be made to not fall down in a screaming heap and kill everyone on board, it could possibly be a suitable fix for the planes physical instability, as long as people piloting the plane were fully aware of what it was doing, why it was there, and had some experience flying the plane without it enabled.
What do you mean by "fix the… plane type"?


Also, whoever let the plane design out with such obvious holes  in the design needs to be seriously investigated (like, did anyone even consider a basic system level FMEA on this thing? that should have pointed out the issue with only one mechanical vane sensor being used as bright as day!)
Yep. As I said, I was only addressing the equipment. But you're right that a root cause analysis will expose the organizational deficiencies that allowed such sloppy work to go out, and it's not gonna look good for Boeing!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 23, 2019, 03:52:58 pm
As I said before, I am not sure this plane will fly again with the same name.
It has a bad reputation and people don't want to fly in it anymore.
You've said it before, and I'll say again that there's a zero percent chance this will happen.

The DC10, for example,

Lets continue over a year and we will see.
Referring to planes of the 70s makes no sense, society has changed too much esp social media, internet....
If airliners are cancelling orders it looks bad, I can't say I can blame them.
Nah. People have always been skeptical of aviation, and so mob mentality around failures has been a constant companion to the industry, even pre-social-media. So yeah, the DC10 is still a valid example.

Airlines cancel orders all the time. It's just basic risk reduction. They'll re-order (the same or something else) once the dust has cleared.

(FYI: "Airliner" means a passenger aircraft for public carriage by an airline. "Airline" means a company who operates such flights.)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 23, 2019, 04:01:03 pm
Nothing in the Corvair was "surprisingly innovative" or ahead of its time. No thing at all. It was just an exercise of cost cutting by bolting down together the worst of the worse to make it cheap, as cheap and bad as a Renault 8 in the 60's or a Dauphine (its predecessor) in the 50's. The only time I've seen on the road with my own eyes a car rolling over for no reason, it was an R8. There's nothing worse when cornering than that swing axle suspension

Clearly you've never driven one, and are not particularly familiar with other American cars of the time. In the era of big lumbering front engine iron V8 powered cars the Corvair came along with a rear mounted alloy case air cooled horizontally opposed 6 cylinder, it was like nothing else out of Detroit at the time. They also offered one of the very first turbocharged engines in a consumer vehicle decades before Saab refined and popularized the technology. It was incredibly innovative for GM, a radical departure from the status quo. Yes it was cheaply made, it was designed to be affordable, it was designed to be fuel efficient which meant small and light weight. It was not high end, but it was nowhere near as bad as many people think based only off Nader's book having never even seen a real Corvair up close. They were no less safe than countless other low cost cars of the era.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 23, 2019, 04:06:01 pm
You can charge for ABS because the DOT says it is legal to sell and drive cars without ABS. At one point cars didn't require a chest belt in the rear seat or air bags up front.
You're confusing ABS and collision avoidance systems, aka autonomous emergency braking (AEB).

This was the original statement:
Automatic braking systems and lane assist are options on cars that are purely for safety. It costs money to implement these things, someone has to pay for it.
By automatic braking system, he means AEB, where the car uses sensors to identify obstacles ahead and apply the brakes automatically. (Sort of an always-on extension of the hardware used for adaptive cruise control.) This is not required by law.

ABS means anti-lock braking system, where the car will automatically pulse the brakes to prevent the wheels from spinning out, retaining steering control in a skid. ABS has been mandatory on all new cars in the EU since 2004, and it's been de-facto mandatory in USA since 2012, when electronic stability control (ESC) became mandatory on new cars. (ESC builds upon ABS, adding more sensors and computing, and the ability for the system to apply brake power, not only release it.) ESC has been mandatory in the EU since 2014.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 23, 2019, 04:14:02 pm
yet people think nothing of getting into a car.
Oh there we go again comparing anything to cars  :palm:
If you do want to compare it you should look at only those accidents with:
- a professional driver
- no alcohol involved
- no other cars or other vehicles/pedestrians involved
- no corners or bad roads, not within city limits (a straight highway without other traffic)
- no speeding or other traffic violations like crossing red lights etc.

If you look at all this the chance of a passenger surviving such an accident with all the safety precautions like airbags, belts, crackle zones is way higher than any passenger in a plane accident.
( please put your head between your legs and brace for impact and oh yeah we put the chairs so close to eachother anyone taller than 1m85 will probably hit the seat in front of him first, nice knowing you). Individual Passenger safety in a plane is the same as in the 50s , it has even been made worse by stuffing more and more people per square meter in that flying can.

So are you asserting that getting into a car is less likely to kill you than getting onto an airliner? I'm not sure you understand how statistics work. What does the chance of surviving an accident have to do with this? The plane is far less likely to crash so even if you have a 99% chance of surviving a car crash and a 1% chance of surviving a plane crash the plane is still far less likely to kill you because plane crashes are extremely rare. They are so incredibly rare that whenever one happens it is front page news and we discuss the incident in threads like this. There are thousands of car crashes every day and many thousands of people die for other reasons every day. Yes having a professional driver would improve your safety, but how many people have one of those? Avoiding drugs and alcohol is obviously a big help, so is putting down the mobile phone but none of that helps when some other idiot hits you, and it happens, every single day.

Don't want to compare it to cars? Fine, here are the top 10 causes of accidental death from 2016. Maybe you can point out where airliner crash is on that list because I don't see it.


    Poisoning (including drug overdose): 64,795, +11.1%
    Motor vehicle: 40,231, -0.2%
    Falls: 36,338, +4.8%
    Suffocation by ingestion, inhalation: 5,216, +8%
    Drowning: 3,709, -2%
    Fires, flames, smoke: 2,812, +3%
    Mechanical suffocation: 1,730, -2.9%
    Natural heat, cold: 1,269, +6.7%
    Struck by, against: 806, +2%, and
    Machinery: 572, -6.2%.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 23, 2019, 05:06:10 pm
So are you asserting that getting into a car is less likely to kill you than getting onto an airliner?
No. I say a car an sich as a vehicle is more safe than an airplane.
It is the circumstances that make it less safe and statistically have more deaths.
That is what i am saying and take for instance the Ford Pinto which was a very unsafe car because if hit from behind the fueltank could explode was avoided and abandoned by customers.
Which is probably what is going to happen to the MAX since for instance in Holland there were three MAX planes from TUI and after the accident people who booked their flight on one of these planes were massively cancelling their trip.
That was the discussion.

Quote
I'm not sure you understand how statistics work.

I know exactly how statistics work and the most important thing is to differentiate from the main subject to investigate vs all circumstantial parameters.
So the subject was NOT is driving a car safer than flying a plane, that was what you made of it so you could make a point. It was is a car safer than a plane.
Yes ofcourse it is, if something malfunctions on a plane in air and you can not control it anymore it is almost 99% game over. In a car it is not since you are still on the ground, you have crackle zones, airbags etc.
So all I am saying is that if a plane has a bad track record people are going to avoid flying on such a plane, that's all.
If they rename the plane and it has a longer safer track record than people will start flying again.
Pure social psychology.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: apis on March 23, 2019, 05:10:32 pm
Yes ofcourse it is, if something malfunctions on a plane in air and you can not control it anymore it is almost 99% game over. In a car it is not since you are still on the ground, you have crackle zones, airbags etc.
Cars are also much more likely to crash into something, since they are still on the ground.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 23, 2019, 05:25:28 pm
Yes ofcourse it is, if something malfunctions on a plane in air and you can not control it anymore it is almost 99% game over. In a car it is not since you are still on the ground, you have crackle zones, airbags etc.
Cars are also much more likely to crash into something, since they are still on the ground.
Yes those are the other parameters as discussed, which is why an autonomous driving car is so much more difficult than an autopilot on a plane.
But thats not the discussion since it is just about the vehicle it self, if a customer has the choice to use a safe vehicle or an unsafe vehicle which will it choose, it is not that complicated.
That was my only point that customers will stay away from the MAX for the coming period, unless it is redesigned, found safe and probably rebranded to another name.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 23, 2019, 05:46:33 pm
Tooki: yeah, ABS might be compulsory on cars in US, now, too. I'm not sure. But I do remember being offered ABS brakes as a ~$500-$1000 option on cars and motorcycles in my day. And I have never ridden a motorcycle with ABS. Point being, until it has been mandated as a requirement, this is ok to do.

AOA were used in commercial planes just to activate a stick shaker until very recently. There was never an AOA display (non military planes). And there was never a reason to need two sensors or double redundancy/agreement to activate a stick shaker stall alert. The stick shaker going off might confuse a pilot the first couple times, but the human response to a stick shaker is unlikely to cause a crash. Only perhaps in zero visibility at low altitude with ASI and/or altimeter both broken and a pilot that still really trusts his stick shaker and does not have the normal human fear of crashing into the ground. This is what the MCAS does; with no input from the horizon, pitch, speed, or thrust, altitude, it will (apparently) blindly respond to AOA sensor. This is why MCAS would need redundancy, per FAA's own guidelines, according to the Seattle Times article.

An AOA display is never going to be super critical in a commercial plane, if not for the MCAS. After a very short takeoff over a mountain, it will tell you that you could take maybe 100 lbs more, next time. But commercial planes are not operated like that. Their weight limit might go up, but it will be through a pile of bureaucracy. AOA display might help Sunday pilots explore the limits of their planes and increase their skills, but commercial pilots aren't allowed to do that. Losing $100 million dollar planes and killing pilots in training would be very costly, nevermind the cost of the fuel. Sticking to strict rules and narrow flight conditions already works fine for passenger transport planes without needing Top Gun pilots. A bus driver might be more capable of handling unusual conditions if Grey Hound taught him how to drift a bus around corners, but that ain't happening, either.

Planes are safer than cars, of course, when adjusted per mile. They travel a lot more in less times. I bet they (commercial) are safer per hour, as well. But even if they weren't safer, they still wouldn't make the top ten list of causes of accidental deaths, because most people don't fly very much, but many people drive several times a week, with a good portion of the world driving at least 5 days a week to work and one day a week to church. You can be captain of a 737 with some thousand of hours of actual flight time. Many of us have spent 100 times that in a car or bus.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: GeorgeOfTheJungle on March 23, 2019, 05:57:11 pm
it was like nothing else out of Detroit at the time.

That's true, but was a change for the worse. GM fooled you, in Europe we have had many cars like that not because they were better, but because they were cheap!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 23, 2019, 07:49:05 pm
[That is what i am saying and take for instance the Ford Pinto which was a very unsafe car because if hit from behind the fueltank could explode was avoided and abandoned by customers.

I remember the Pinto hysteria, and that's what it was to a large extent. It ended up in a massive recall (major at the time, pretty minor by todays standards) to install a plastic barrier and a new filler tube, and people kept driving them for another decade or more (I know of one still on the road today, there are probably a few more). Legal scholars have since written volumes about public perception vs actual facts in the courtroom.

If you actually look at the statistics for fatalities in cars for those years, you'd notice that the Ford Pinto was about average for cars of its type (subcompacts). And it was significantly better than some, such as the VW Beetle or the AMC Gremlin.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 23, 2019, 09:31:40 pm
How far can you go offtopic
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 23, 2019, 10:03:14 pm
How far can you go offtopic
I wasn't the one who brought up the Ford Pinto (and Mercury Bobcat rebadge) as an example, but since you did, I gave you the benefit of my first-hand memories of it. Showing my age and still-decent memory.

I would have stuck with aviation disasters as examples of things the public got over myself...the DC-10 cargo door failures, the 737 rudder failures, or even the 727 inadequate training crash-landings (3 of them in a 3-month period) when the plane was still new.

Public hysteria is very much on topic. This thread wouldn't exist without it. History teaches us that this too will pass.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: james_s on March 23, 2019, 10:18:04 pm
No. I say a car an sich as a vehicle is more safe than an airplane.


You're cherry picking and ignoring the big picture which is this. If you travel a given number of miles in a plane and the same number of miles in a car, you are more likely to die in the car, period. This is a mathematically demonstrable fact, it is not a matter of opinion or up for debate. Do you need me to provide the statistics?

Obviously it's because airplanes are far less likely to crash per mile traveled, not because of survivability. Nobody is saying that car accidents are not more survivable than plane crashes, but there are so many more of them that your risk of dying in one is far higher. Throughout my life I've been in at least 10 car accidents, most of them minor and none of them my fault but they happened none the less and one I was very lucky to walk away from. I've flown quite a bit too and I've been in zero plane crashes. Plane crashes are extraordinarily rare, hence flying is quite safe.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 23, 2019, 10:32:17 pm
Quote from: Nusa link=topic=147
Public hysteria is very much on topic. This thread wouldn't exist without it. History teaches us that this too will pass.[/quote
Fair enough, we will see what happens. I do 't think it will kill Boeing, as other people said too many existing carriers will have a huge problem when Boeing is gone. It will be impossible to retrain all pilots and technicians to Airbus planes so that is not going to happen IMO.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 23, 2019, 10:48:48 pm
You're cherry picking and ignoring the big picture which is this. If you travel a given number of miles in a plane and the same number of miles in a car, you are more likely to die in the car, period. This is a mathematically demonstrable fact, it is not a matter of opinion or up for debate. Do you need me to provide the statistics?

No every child knows that this is not my point, you don't get it or don't want to get it.
Last time:
It is not the car that is less safe than the plane, it are the conditions in which people travel in car that is less safe than a plane.
If you do the same precautions with driving cars as flying a plane or vice versa if you let everybody even drunk fly 1000's of planes right across a small airspace you have the same amount of accidents.

I will try to visualize my point:

Car: You have to be a professional driver, do 200 hours of driving each year or your license is revoked. You need to be healthy , sober, do a thorough engine and car safety check before you start the car.
After every drive the tires are checked,brakes, fluid levels etc. etc.
You have to wait till travel control will tell you when you can drive away in your car, and exactly what route you should take. Travel control will make sure you encounter no other trafic within a mile, no cars , no bikes, no pedestrians or animals and that the entire road is clear for you to drive. If the weather gets very bad travel control will tell you to stop your car at the nearest possibility. Your speed is controlled, the time for your travel is controlled and you are not allowed to deviate from your path. In case you don't feel well there is a second professional driver besides you to take over.

Plane: 1000s of planes are behind eachother flying with less than 30seconds of distance from eachother, you have to look left and right all the time since there could be planes coming without warning even with drunk pilots or pilots that only got their license a day ago and do not know how fly very well. Also some other aircraft like drones or even missiles might come out of nowhere so be warned to keep an eye out. If the weather is very bad it is up to you if you continue flying even with zero visibilty, hopefully the planes before and after you have the same pace or a lot of them will crash into eachoter which is not good but happens all the time, esp. during rush hour when everyone is flying their planes to work.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 23, 2019, 11:32:25 pm
Quote
the thing is, having an inherently aerodynamically unstable airframe and using software to make it what I'll call "apparently stable" to the pilots is a completely valid design approach. (Think of the Segway scooter, which is only possible because of software.)
To expound on this, one has to wonder if the MCAS system is adequate to even do this.

Take for example the anti-stall on an Airbus A330. During the Quantas incident, in response to (albeit erroneous) AOA information, the plane  dipped very decisively at -0.8G. This was 1.8G, absolute! Yes, people bounced off the roof of the plane and some people suffered spinal cord injuries. In the Airbus, the flight computer has control over the elevators, not just the stabilizer. Compare that to the MCAS system that can make only gradual (but ultimately gigantic) changes to the attitude of the plane (and apparently won't undo this change AFTER), and you wonder how sloppy and inadequate a bandaid this is to begin with.

Compared to an Airbus, or even a Segway, the way the news has reported the MCAS makes it sound like Mickey Mouse dog poo which only billions of dollars of incentive could make it look like anything else to anyone.

When Airbus made the decision to retrofit their planes with larger engines to make the A320, Boeing engineers and executives thought it would be a bad decision for Airbus. They realized this would cause some major problems. When the 320 was successful, they tried to follow suite.

So when Boeing says they hid the MCAS system because they didn't want to overload pilots with too much information, that is not easy to believe. They tried to do the same thing Airbus did, but with the additional problems of the 737 being too low to the ground; the 737 handling cannot be tweaked by software to the same degree as the Airbus; and messing with the trim also subverted one of Boeing's core tenants and selling points.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 26, 2019, 03:21:10 am
No 737 MCAS, no burning Tesla battery, just the tranquility of 777 electric motor whine. :popcorn:
https://www.youtube.com/watch?v=OAiJxw7v9tw (https://www.youtube.com/watch?v=OAiJxw7v9tw)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 26, 2019, 03:41:57 am
That was my only point that customers will stay away from the MAX for the coming period, unless it is redesigned, found safe and probably rebranded to another name.

I still disagree.

What I think will happen is that the truth of whatever happened will come out and that there will be some obvious actions necessary.  Depending on the nature of the issues identified, there may also be hell to pay - and that payment will be made.

Once the dust settles and the required changes have been implemented, the travelling public will be back on the MAX and if nothing further goes wrong over the ensuing year, then these two crashes will be all but forgotten by them.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 26, 2019, 04:45:50 am
Boeing will shortly be finished with their MCAS software fix, but who has confidence in it given the original software design was so poorly done and made it through testing and certification?
What makes the checks any better for this software iteration? How's the rest of the aircraft's design, testing, certification?

I think Boeing's corporate arrogance is going to be seen in full display as they try get the grounded planes back in the air as soon as possible. The pilot training takes time, it will be months before the planes are up and the CEO is still bungling the PR around the entire debacle.

The politics around this is nuts. Trade war fuelled, today: "Airbus SE secured a $35 billion jet deal from China"
Ouch.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: BradC on March 26, 2019, 07:21:30 am
Boeing will shortly be finished with their MCAS software fix, but who has confidence in it given the original software design was so poorly done and made it through testing and certification?

I'll have confidence in it given :
A) what this will have (and is going to) cost them;
B) the extreme scrutiny that will be applied by the international aviation community; and
C) the requirement to demonstrate to the flying public that these aircraft are airworthy.

Despite the odd oops (and this is a big one), there is a reason a considerable amount of the aviation world says "if it ain't Boeing, I ain't going".

Planes fall out of the sky. They always have, and they always will. The takeaway is always the lesson(s) learned and how they apply that moving forwards.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Kjelt on March 26, 2019, 07:56:20 am
Despite the odd oops (and this is a big one), there is a reason a considerable amount of the aviation world says "if it ain't Boeing, I ain't going".

That slogan started when the 707 came, the 60s  :)

Boeing publishes a list of planes that never had a crash,
ofcourse the longer a plane is in service , the more it is used , the higher the chance something happens.

Quote from: https://www.tripsavvy.com/the-safest-aircraft-54428
The Safest Aircraft in the World
There are 10 major commercial jet aircraft that can claim to be the world’s safest after never recording a passenger fatality, according to Boeing. The annual Boeing Statistical Summary of Commercial Jet Airplane Accidents Worldwide Operations 1959 – 2016 lists the following aircraft as having a fatality-free record:


Boeing 717 (formerly the MD95)
Bombardier CRJ700/900/1000 regional jet family
Airbus A380
Boeing 787
Boeing 747-8
Airbus A350
Airbus A340
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: tooki on March 26, 2019, 10:05:40 am
Quote
the thing is, having an inherently aerodynamically unstable airframe and using software to make it what I'll call "apparently stable" to the pilots is a completely valid design approach. (Think of the Segway scooter, which is only possible because of software.)
To expound on this, one has to wonder if the MCAS system is adequate to even do this.

Take for example the anti-stall on an Airbus A330. During the Quantas incident, in response to (albeit erroneous) AOA information, the plane  dipped very decisively at -0.8G. This was 1.8G, absolute! Yes, people bounced off the roof of the plane and some people suffered spinal cord injuries. In the Airbus, the flight computer has control over the elevators, not just the stabilizer. Compare that to the MCAS system that can make only gradual (but ultimately gigantic) changes to the attitude of the plane (and apparently won't undo this change AFTER), and you wonder how sloppy and inadequate a bandaid this is to begin with.

Compared to an Airbus, or even a Segway, the way the news has reported the MCAS makes it sound like Mickey Mouse dog poo which only billions of dollars of incentive could make it look like anything else to anyone.

When Airbus made the decision to retrofit their planes with larger engines to make the A320, Boeing engineers and executives thought it would be a bad decision for Airbus. They realized this would cause some major problems. When the 320 was successful, they tried to follow suite.

So when Boeing says they hid the MCAS system because they didn't want to overload pilots with too much information, that is not easy to believe. They tried to do the same thing Airbus did, but with the additional problems of the 737 being too low to the ground; the 737 handling cannot be tweaked by software to the same degree as the Airbus; and messing with the trim also subverted one of Boeing's core tenants and selling points.
You completely misunderstand and misconstrue the circumstances.

It’s not as though the MAX handles radically differently, or is particularly unstable. (Software stability control has been used in flying wing aircraft, which are so unstable as to be practically unflyable by a human. But software can do it, presenting to a pilot an “apparently stable” aircraft. The 737 MAX is a much, much less demanding situation.) It’s a single handling characteristic that separates its handling from any older 737: its lift characteristics at high AOA. This single thing is trimmed in software not to make it easier on pilots, but to make the MAX retain the same type rating so that 737 pilots don’t need to be retrained and recertified in the MAX. This isn’t something where you’d want quick, sudden changes anyway, which is why it only controls the jackscrew in the back.

As I said earlier, Boeing made two technical mistakes: relying on a single AOA sensor (leading to a single point of failure), and allowing MCAS to re-trigger repeatedly without limiting its cumulative control input. And then the organizational mistakes were to not document the system and train pilots and airlines on it and how to disable it.

P.S. It’s “tenets”, not “tenants”. ;)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Obi_Kwiet on March 26, 2019, 03:01:45 pm
It's also worth noting, that pilots already know how to recover an MCAS fault. The MCAS is just an input to the auto trim system, which is disabled with the same switches that it always has been. While the system level design for the MCAS allowed for an unnecessarily high and extreme failure rate, the pilots theoretically already had everything they needed to diagnose and correct the fault.

The corrective action for an MCAS failure is simply the trim runaway checklist, which is a memory item. The argument being made is that an MCAS failure makes trim runaway harder to notice because the control input happened in bursts instead of continuously, and while that's true, I don't think it excuses the pilots. If you are fighting with a fault for eleven minutes, and during that time both crew-members fail to check one of the two control surfaces that could be directly responsible for that fault, then the crew's ability to fault find under pressure is unacceptably poor. Not every problem will look exactly like a scenario you have been shown before. We aren't talking about complex inferences here, we are talking about checking to see if a thing that points the nose down is pointing the nose down. At some point over an eleven minute period of the nose being pointed down.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: MT on March 26, 2019, 03:58:01 pm
The politics around this is nuts. Trade war fuelled, today: "Airbus SE secured a $35 billion jet deal from China"
Ouch.
Indonesian airline Garuda cancells 49 Boeing 737 MAX 8 $4.9 billion

Now FFA suddenly and "tentatively" certifies Boing MCAS to only dip nose for 10 secs and only once! Geeeee! :palm:
https://gizmodo.com/boeing-software-updates-to-fix-anti-stall-system-tentat-1833521139

Quote
Boeing CEO, president, and chairman Dennis Muilenburg said in a statement at the time that while it maintained “full confidence” in the model’s safety, the suspension was issued “out of an abundance of caution.”

“Safety is a core value at Boeing for as long as we have been building airplanes; and it always will be. There is no greater priority for our company and our industry,

No its not Boings core values you deepstate psychopathic asshole, its to make money else you would not have had a man-cave certified faulty design to begin with!
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 26, 2019, 08:44:44 pm
^That's not reassuring.
Firstly, there should be a way to disable MCAS without cutting out trim power. I don't see why not. Whether the flight goes on as planned or make an unplanned or emergency landing, why make the pilot use the crankwheels on top of that.

Quote
It’s not as though the MAX handles radically differently, or is particularly unstable. (Software stability control has been used in flying wing aircraft, which are so unstable as to be practically unflyable by a human. But software can do it, presenting to a pilot an “apparently stable” aircraft. The 737 MAX is a much, much less demanding situation.) It’s a single handling characteristic that separates its handling from any older 737:
It is stable as long as AOA is kept below what the 737 NG can do. It is admittedly UNSTABLE at high AOA. Unstable as in runaway towards stall. As previously discussed, there is nothing that MCAS does to make the MAX handle like the NG, despite how it is spun. More thrust makes the plane nose up. MCAS doesn't do anything to make the MAX not do this. It's only after it reaches or approaches an AOA where the NG would still be stable that the MCAS kicks in and says "no don't do that."

For an electronic doodad to make an area of runaway instability stable, it has to be able to react quickly. Making a static change to the stabilizer does not change the fact that the change in lift of the engine "nacelles" is NOT static. It increases with more nose up. Still unstable, no matter what static change you make as a bandaid. MCAS is maybe there to prevent the plane from reaching that point. It's only a "less demanding situation" because this high of an AOA would not be necessary except in unusual circumstances.

This is a big bag of conjecture, for sure. I am guessing from what we know. Maybe I'm wrong, but I think you could be wrong, too. I'm just speculating. If MCAS trim adjustment can actually keep up with this change in nacelle lift at high AOA... great. But the way MCAS has been described doesn't jive with this. To counterbalance the varying nacelle lift at varying AOA, the trim should have to be adjusting in an absolute way based on AOA. And in both directions. Not making relative adjustments, down only.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Nusa on March 26, 2019, 09:24:08 pm
Remember there are two pilots in that cockpit. If the trim has to be adjusted manually instead of electrically, there's going to be a another hand available to do something if the flying pilot asks. Even in regular operation it's normal to verbally delegate some actions to the other pilot.

You're making too big a fuss about the word unstable. An SUV is admittedly more unstable than a sports car in a turn. The solution is to not take turns too fast in the first place, not scream and yell until SUV's are banned.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 26, 2019, 09:30:56 pm
I'm looking at the word unstable as an engineer and from what we have been told. Instable has en engineering implication that is beyond "the plane will shake a little."

Quote
An SUV is admittedly more unstable than a sports car in a turn.
Not necessarily. An SUV might not be able to pull as many lateral G's, but it might be more stable, controllable, and recoverable in the event of loss of traction of the tires.

Take for example the Porche Carrera GT. In most other Porches and in many other (esp rear-drive) cars, the car can be oversteered in a predictable manner when the tires break loose. Some cars can be intentionally drifted on demand, even, with great control through the entire process. The Porche Carrera GT doesn't like to do this. Even an experienced driver cannot control this car when this happens, even if he expects it.
 
Some cars give more warning at the edge of traction. Some are more controllable and/or recoverable. It doesn't necessarily mean they are capable of lower lap times. The Carrera GT will run circles around the SUV... up until the driver exceeds the car's limit. There will be no warning, and at this point the driver is just along for the ride. He isn't going to lose 3 seconds on his laptime after recovering from a little slide. The car will spin out and go off the track, and he will be done for the day.

I'ver personally "drifted" a car unintentionally, twice. Once on an on-ramp that had iced. I had my car pretty near sideways. Second was on dry pavement. Country highway with 2 lanes in fog. Someone decided to park in the left lane with no lights on, and by the time I saw it, I could only swerve to the other lane. Probably avoided hitting the car by something like 10 feet at most. When I steered back to the left to stay in the right lane, my car's rear slid out by about 30 degrees. Both times I recovered with no problem and stayed on the road, because I knew what was happening and I knew what to do. And... the car was stable and predictable and controllable under that condition. Just ride it out. Apply oversteer to keep the front tires in the right direction, and the the car will eventually return to straight. You just have to expect that response and return the wheel to center as it does so, because it can happen fast. My passengers were pretty impressed, though.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: floobydust on March 26, 2019, 10:24:14 pm
Flight simulations recreating the problems with the Lion Air plane, pilots discovered that they had less than 40 seconds to override MCAS.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Obi_Kwiet on March 26, 2019, 11:12:51 pm
In an engineering sense, stability means that a lack of control input will causes the system to return to a steady state. Unstable means that a system with no control input will begin to deviate from its current state at an increasing rate. More stability comes with the cost that the system tends to be less responsive.

Things like cars slipping are scenarios where the system becomes strongly nonlinear and controlablity suffers. Stability isn't really the right thing to worry about. It's more that we are talking about operating regions with very different system dynamics which the operator may not know how to respond to, or the system may enter a region where it is no longer controllable due to actuator limits.

MCAS was designed to deal with a situation where the system was not controllable with elevator inputs, so an auto trim assist was added in that state region to make the system controllable. Stability/instability aren't really relevant there. In fact, this isn't even an issue of a strong non-linearity, it's just an issue of running into an actuation limit on the elevator control surface. The trim basically gives the elevators a boost.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: blueskull on March 26, 2019, 11:14:17 pm
And a new 737 MAX incident. An empty MAX on its way ferrying to the storage suffered from an engine failure and was returned to Florida.
The media and general public definitely isn't going to take this well.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 26, 2019, 11:43:17 pm
Quote
Stability/instability aren't really relevant there. In fact, this isn't even an issue of a strong non-linearity, it's just an issue of running into an actuation limit on the elevator control surface. The trim basically gives the elevators a boost.

Great theory, but here are the holes. If MCAS basically gives the elevators a necessary boost, you're suggesting full elevator down wouldn't even prevent the plane from runaway nose up stall when in a condition where the NG would be considered to still be in a normal part of its envelope. Where the NG would still be stable, and by your definition, stable means the NG would return towards straight even if you let go of the stick, let alone push the stick forward. So the MCAS has to kick in and help the pilot do something he wouldn't even do. If he thinks he can just let go of the stick, and the plane will be stable, why would he push full forward?

By your reasoning:
1. Ideally, the MCAS would not even be needed. They would make the elevator larger and more powerful. They could even limit the upwards range a bit, to ensure that upwards elevator is not increased. Only the downwards effect is increased. Of course this might not be possible without major alterations and cost and time and recertification, and perhaps due to these reasons it would be better to just build a new plane from scratch, even though it sounds simple.

2. If the MCAS is only supposed to boost or extend the pilot's response, then it would ideally only activate when the pilot is already at full elevator down. MCAS would not do anything if the pilot is not at full elevator down. In the case of these crashes, the pilots were obviously giving full elevator UP. But maybe trim control is too slow for this to work and/or maybe as I suggested earlier, an NG pilot wouldn't even know to push the stick that far forward until it was too late.

Any way you slice it, it would appear that MCAS is potentially a pathetic bandaid on a pretty serious wound.

So no. I think non-linearity and instability are potentially a big part of the problem. If Boeing were willing to eat it and redesign/recertify a new airframe, they would have made the plane with taller landing gear so the engines did not have to mount in a way that produced instability in a given AOA range where the plane still has laminar flow and lift. To me, "unstable" potentially means that even if the pilot had the range of control (with help of MCAS or otherwise) to reign the plane back from here, this area of AOA would be difficult to control and essentially unsafe/unusable without some active electronic aid that can respond relatively quickly and dynamically... not just to slam the nose back down, but to enable the pilot to utilize and fly in this range of AOA in a predictable and controllable manner if and when the need should arise. If and when then need should arise, slamming the nose down might be less than ideal.

Quote
they had less than 40 seconds to override MCAS.
Which means cutting the stab trim and then cranking the wheel, which Djacobow suggests it is maybe 1/3 to 1/2 as fast without power. If they had already allowed MCAS to turn the wheels all the way down, taking 20 seconds with power... That would be a fun challenge of how much motor coordination do you have while spearheading into the ocean. On one of those flights, I read the plane was pitched 49 degrees down. Even 30 degrees is pretty steep. San Franciso's steepest streets are around 30 degrees, if you've ever driven there. It's unnerving on a road.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error
Post by: SkyMaster on March 27, 2019, 01:20:45 am
It's also worth noting, that pilots already know how to recover an MCAS fault. The MCAS is just an input to the auto trim system, which is disabled with the same switches that it always has been. While the system level design for the MCAS allowed for an unnecessarily high and extreme failure rate, the pilots theoretically already had everything they needed to diagnose and correct the fault.

The corrective action for an MCAS failure is simply the trim runaway checklist, which is a memory item. The argument being made is that an MCAS failure makes trim runaway harder to notice because the control input happened in bursts instead of continuously, and while that's true, I don't think it excuses the pilots. If you are fighting with a fault for eleven minutes, and during that time both crew-members fail to check one of the two control surfaces that could be directly responsible for that fault, then the crew's ability to fault find under pressure is unacceptably poor. Not every problem will look exactly like a scenario you have been shown before. We aren't talking about complex inferences here, we are talking about checking to see if a thing that points the nose down is pointing the nose down. At some point over an eleven minute period of the nose being pointed down.

This ^^^^^^^^^ is correct.

The Lion Air crew failed to identify the run away trim condition (Boeing calls it "Runaway Stabilizer") and/or did not take the appropriate corrective action.

The corrective action was very simple; set the Stabilizer Trim Cutout switches to CUTOUT.

MCAS or not; this was a "Runaway Stabilizer" condition.

Maybe the crew was confused because in addition to the trim runaway condition, the stick shaker was also activated. But this is my own speculation on the crew confusion.

The fault that activated the MCAS trim, also triggered the stick shaker.

The fact is; the crew did not take the appropriate corrective action for a "Runaway Stabilizer" condition.

You cannot miss when the Stabilizer Trim is being activated in a 737, as there is a loud bicycle chain noise coming from the center pedestal and you can see the large Trim Wheels rotating.

The Boeing 737 MAX is just like the 737 NG and the 737 "Classic"; a hands and feet aircraft. Once the Stabilizer Trim is in the Cutout position, it is still possible to trim the aircraft using the trim wheel, which is mechanically connected to the Horizontal Stabilizer Jack Screw. I suppose this is the same horizontal stabilizer trim system that Boeing had on the 707 and 727.


May the passengers and crew of Lion Air flight 610 rest in peace.
 :(
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 27, 2019, 01:26:20 am
^^^^
Quote
As for pilot reaction: If you are used to hearing this thing clacking away during autopilot trim adjustments, then you might not notice it, at all? During AF447, the audio stall warning went off 70 times for over 2 minutes, and the black box recordings suggest that the pilots never even discussed a stall. Some studies have suggested that audio warnings don't register to the pilot under many circumstances, which is why most of the important alerts are not audio, only.

So, when the MCAS goes haywire, the pilots immediate reaction might be nothing. Then after awhile, they might have either tuned out the trim wheel adjusting altogether. Or they might realize, "hey, that trim adjustment has been going on for longer than usual." They might then first wonder why autopilot is turned on when they are sure it is off. Then they might turn off the autopilot (redundantly). Say for sake of speculation that the MCAS just happened to finish doing its thing at the time the pilot pushes the autopilot disengage button. Then he pushes the manual trim button, to get the trim back up. And it works as he expects. Problem solved... but not yet. It happens again. And pilot is on the wrong road from here on out.

Simply knowing MCAS existed could make a huge difference in response.

One of your primary algorithms when flying this plane might be that if instruments are malfunctioning, you can always turn off the autopilot and fly, manually. When you think the autopilot is turning itself on/off and malfunctioning, then you might get some panic and tunnel vision, because your major "out" and feeling of control and safety has been removed. Now your tunnel vision has you locked on the autopilot disengage button, because hitting it seemed to have worked the first time, and now you think the autopilot is trying to kill you. It's obviously not a runaway trim, because it seems to have something to do with the autopilot, and it is not continous. When you press the trim up, it works. When you press trim down, that works. Trim controls are working. Training was maybe very specific under what condition you cut the stab trim, and in the moment the pilot is probably reverting to training and not able to think so clearly due to being so close to death at a fairly low altitude. He's not able to reason that cutting stab trim will prevent autopilot from using it, too (or MCAS, secret autopilot that is the "manual" autopilot).  He is following his checklist.

On top of that this was the crew's first flight on a MAX. All the controls are different. Video displays replacing gauges. I can spend an hour looking for something on my own bench that is in plain sight, as it is.

The AF447 crew was western Europeans. The altimeter was never broke. The airspeed indicator came back to life in plenty time. The stall warning went off for 3 minutes. No one even said the word stall for over two minutes, until it was too late, anyway. When the captain returned to the cabin and they asked him what to do, his exact words translate to "fuck if I know." If cutting stab trim is flying 101, how bout knowing what a stall is? They put engines on full the entire time, so they didn't think the plane was going too fast and experiencing Mach turbulence. They knew the plane was dropping and their air speed was low.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SkyMaster on March 27, 2019, 01:50:29 am
On top of that this was the crew's first flight on a MAX. All the controls are different. Video displays replacing gauges. I can spend an hour looking for something on my own bench that is in plain sight, as it is.

The instruments panel, pedestal, overhead panel and flight controls on the 737 MAX are the same as on the previous 737 NG. And everything is so antiquated in a 737 NG, that it has to be the same as the 737 "Classic". Anyway, they have to be the same, as they all share a common Type Rating.


The flight instruments on the 737 MAX are different.


What was the flight crew flying before?

737 NG  do not have gauges, but LCD screens. LCD screens in the 737 MAX are larger than the screen in the 737 NG, the 737 MAX probably use large screen similar to the 787.

I doubt an airline would expect pilots trained on the 737 "Classic" to jump into a 737 NG or 737 MAX without any transition training, as the information on LCD screen is not shown the same way as on steam gauges.

 :)
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: KL27x on March 27, 2019, 01:52:25 am
What about the other stuff? The autopilot makes trim adjustments, right? The trim wheel moving itself is something the pilots would be accustomed to, and something they would attribute to the autopilot, no?
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Brumby on March 27, 2019, 01:56:40 am
The instruments panel, pedestal, overhead panel and flight controls on the 737 MAX are the same as on the previous 737 NG. And everything is so antiquated in a 737 NG, that it has to be the same as the 737 "Classic". Anyway, they have to be the same, as they all share a common Type Rating.

Any difference between models is a potential point of defining the need for a new Type Rating - which becomes a costly exercise across the board.  That's why they try and keep things as unchanged as possible.  For example, the switch for the "No Smoking" sign is still in place, even though it hasn't been needed for many years.  Removing it "changes" the aircraft.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: SkyMaster on March 27, 2019, 02:11:40 am
What about the other stuff? The autopilot makes trim adjustments, right? The trim wheel moving itself is something the pilots would be accustomed to, and something they would attribute to the autopilot, no?

Your question is very good, and Boeing answer is very simple. The Boeing 737 Quick Reference Handbook (commonly known as QRH) reads, under "Runaway Stabilizer":

Condition: Continuing rotation of the stabilizer trim wheel in a manner not appropriate for flight conditions.
Autopilot (if engaged): DISENGAGE
If runaway continues:
Stabilizer Trim Cutout switches: (set to) CUTOUT

The contents of the QRH is supposed to be known by the pilots who are type rated in the aircraft they are flying. The 737 QRH Quick Action Index is one page of 15 items written in bold.
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on March 27, 2019, 02:15:22 am
The politics around this is nuts. Trade war fuelled, today: "Airbus SE secured a $35 billion jet deal from China"
Ouch.
Indonesian airline Garuda cancells 49 Boeing 737 MAX 8 $4.9 billion

Ouch
Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: EEVblog on March 27, 2019, 02:26:09 am
Wow, the same plane had the same incident the day before, and a pilot in the jump seat knew what to do and saved the plane:
https://www.smh.com.au/business/companies/pilot-who-hitched-a-ride-saved-boeing-737-max-a-day-before-it-crashed-20190320-p515sq.html (https://www.smh.com.au/business/companies/pilot-who-hitched-a-ride-saved-boeing-737-max-a-day-before-it-crashed-20190320-p515sq.html)

 

Title: Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
Post by: Obi_Kwiet on March 27, 2019, 02:52:03 am
Quote
Stability/instability aren't really relevant there. In fact, this isn't even an issue of a strong non-linearity, it's just an issue of running into an actuation limit on the elevator control surface. The trim basically gives the elevators a boost.

Great theory, but here are the holes. If MCAS basically gives the elevators a necessary boost, you're suggesting full elevator down wouldn't even prevent the plane from runaway nose up stall when in a condition where the NG would be considered to still be in a normal part of its envelope. Where the NG would still be stable, and by your definition, stable means the NG would return towards straight even if you let go of the stick, let alone push the stick forward. So the MCAS has to kick in and help the pilot do something he wouldn't even do. If he thinks he can just let go of the stick, and the plane will be stable, why would he push full forward?

By your reasoning:
1. Ideally, the MCAS would not even be needed. They would make the elevator larger and more powerful. They could even limit the upwards range a bit, to ensure that upwards elevator is not increased. Only the downwards effect is increased. Of course this might not be possible without major alterations and cost and time and recertification, and perhaps due to these reasons it would be better to just build a new plane from scratch, even though it sounds simple.

2. If the MCAS is only supposed to boost or extend the pilot's response, then it would ideally only activate when the pilot is already at full elevator down. MCAS would not do anything if the pilot is not at full elevator down. In the case of these crashes, the pilots were obviously giving full elevator UP. But maybe trim control is too slow for this to work and/or maybe as I suggested earlier, an NG pilot wouldn't even know to push the stick that far forward until it was too late.

Any way you slice it, it would appear that MCAS is potentially a pathetic bandaid on a pretty serious wound.

So no. I think non-linearity and instability are potentially a big part of the problem. If Boeing were willing to eat it and redesign/recertify a new airframe, they would have made the plane with taller landing gear so the engines did not have to mount in a way that produced instability in a given AOA range where the plane still has laminar flow and lift. To me, "unstable" potentially means that even if the pilot had the range of control (with help of MCAS or otherwise) to reign the plane back from here, this area of AOA would be difficult to control and essentially unsafe/unusable without some active electronic aid that can respond relatively quickly and dynamically... not just to slam the nose back down, but to enable the pilot to utilize and fly in this range of AOA in a predictable and controllable manner if and when the need should arise. If and when then need should arise, slamming the nose down might be less than ideal.