Author Topic: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'  (Read 13085 times)

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Offline station240

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #25 on: October 31, 2018, 04:56:05 am »
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.
 

Online janoc

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #26 on: October 31, 2018, 05:02:03 am »
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.

« Last Edit: October 31, 2018, 05:06:06 am by janoc »
 

Offline Jr460

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #27 on: October 31, 2018, 05:08:02 am »
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.
 

Offline edy

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #28 on: October 31, 2018, 06:55:53 am »
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.
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Online boffin

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #29 on: October 31, 2018, 07:13:13 am »
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)


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Online Kleinstein

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #30 on: October 31, 2018, 07:52:48 am »
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.
 

Offline Jr460

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #31 on: October 31, 2018, 07:58:30 am »
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.
 

Offline floobydust

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #32 on: October 31, 2018, 08:03:20 am »
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

 

Offline tautech

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #33 on: October 31, 2018, 08:11:21 am »
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
Yep.
Adding to this, if you then only have ground speed (GPS) to work with and a 100kt tailwind things won't end well.
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Offline rx8pilot

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #34 on: October 31, 2018, 08:32:41 am »
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.
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Offline EEVblog

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #35 on: October 31, 2018, 08:59:47 am »
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.
 

Offline sokoloff

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #36 on: October 31, 2018, 09:02:41 am »
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.
« Last Edit: October 31, 2018, 09:04:47 am by sokoloff »
 

Offline alsetalokin4017

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #37 on: October 31, 2018, 09:15:15 am »
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.


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Offline EEVblog

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #38 on: October 31, 2018, 09:31:24 am »
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.
« Last Edit: October 31, 2018, 09:33:53 am by EEVblog »
 

Offline MT

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #39 on: October 31, 2018, 09:59:53 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

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
« Last Edit: October 31, 2018, 10:02:28 am by MT »
 

Offline Lord of nothing

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #40 on: October 31, 2018, 10:03:23 am »
Quote
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o you share? I use a proper Equipment for.
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Offline EEVblog

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #41 on: October 31, 2018, 10:04:53 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?
 

Offline edy

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #42 on: October 31, 2018, 04:37:14 pm »
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

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:

« Last Edit: October 31, 2018, 04:39:17 pm by edy »
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Offline Lord of nothing

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #43 on: October 31, 2018, 08:41:22 pm »
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.
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Offline nfmax

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #44 on: October 31, 2018, 08:55:44 pm »
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).
 

Online janoc

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #45 on: October 31, 2018, 09:38:17 pm »
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


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

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.

« Last Edit: October 31, 2018, 09:45:55 pm by janoc »
 

Offline amyk

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #46 on: October 31, 2018, 10:54:50 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 ?
 

Online janoc

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #47 on: November 01, 2018, 02:47:38 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 ?

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.

« Last Edit: November 01, 2018, 02:53:34 am by janoc »
 

Offline sokoloff

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #48 on: November 01, 2018, 03:54:07 am »
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).
 

Offline raptor1956

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #49 on: November 01, 2018, 04:29:05 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.  ::)

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
 


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