Author Topic: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'  (Read 178215 times)

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Offline Nusa

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #625 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.
 

Offline james_s

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #626 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.
 

Offline Kjelt

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #627 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.
 

Offline Kjelt

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #628 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.
« Last Edit: March 23, 2019, 10:50:32 pm by Kjelt »
 

Offline KL27x

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #629 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.
« Last Edit: March 24, 2019, 11:05:38 pm by KL27x »
 

Offline MT

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #630 on: March 26, 2019, 03:21:10 am »
No 737 MCAS, no burning Tesla battery, just the tranquility of 777 electric motor whine. :popcorn:
 

Offline Brumby

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #631 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.
 
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Offline floobydust

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #632 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.
 

Offline BradC

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #633 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.
 
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Offline Kjelt

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #634 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.

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
 

Offline tooki

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #635 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”. ;)
 

Offline Obi_Kwiet

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #636 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.
« Last Edit: March 26, 2019, 03:03:22 pm by Obi_Kwiet »
 

Offline MT

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #637 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!
« Last Edit: March 26, 2019, 04:06:17 pm by MT »
 

Offline KL27x

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #638 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.
« Last Edit: March 26, 2019, 09:12:32 pm by KL27x »
 

Offline Nusa

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #639 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.
 
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Offline KL27x

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #640 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.
« Last Edit: March 26, 2019, 11:15:27 pm by KL27x »
 

Offline floobydust

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #641 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.
 

Offline Obi_Kwiet

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #642 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.
 
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Offline KL27x

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #643 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.
« Last Edit: March 27, 2019, 01:23:09 am by KL27x »
 

Offline SkyMaster

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error
« Reply #644 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.
 :(
« Last Edit: March 27, 2019, 01:22:29 am by SkyMaster »
 
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Offline KL27x

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #645 on: March 27, 2019, 01:26:20 am »
^^^^
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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.
« Last Edit: March 27, 2019, 01:50:30 am by KL27x »
 

Offline SkyMaster

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #646 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.

 :)
 
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Offline KL27x

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #647 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?
 

Offline Brumby

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #648 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.
 
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Offline SkyMaster

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #649 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.
 


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