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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 24th Apr 2019, 07:34
  #4261 (permalink)  
 
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There is a lot of drivel written here quite obviously from people who have never flown a B737, have no real understanding of swept wing aerodynamics yet appear willing to pontificate on how the pilots should have gone back to basics etc etc. The MCAS system was built into the Max, no information was given to the pilots who then found themselves with a stabilizer so far out that essentially and eventually left zero elevator authority. Ambiguity for experienced 737 pilots would partly be due to the speed trim system which also operates independently of the pilots. I have the greatest sympathy for the pilots in these terrible accidents and not sure how I would have reacted. I usually avoid the willy waving but I have over 10,000 hours 737, mainly pic plus usual training qualifications. You 20/20 hindsight experts must be utterly brilliant of course.
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Old 24th Apr 2019, 07:46
  #4262 (permalink)  
 
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Originally Posted by DaveReidUK View Post
I'd be very interested to see a reference that says that.
I can't find primary references stating that, other than the text and chart by LEOCh previously mentioned: https://www.pprune.org/rumours-news/618252-boeing-737-max-software-fixes-due-lion-air-crash-delayed-post10423226.html

The best simple description is a single sentence from b737.org.uk: 737 MAX - MCAS
After AoA falls below the hysteresis threshold (0.5 degrees below the activation angle), MCAS commands nose up stabilizer to return the aircraft to the trim state that existed before the MCAS activation.
Edit: There is an intriguing extra sentence (mangled meaning?) about the proposed improvements:
Furthermore the logic for MCAS to command a nose up stab trim to return to trim following pilot electric trim intervention or exceeding the forward column cutout switch, will also now be improved.

Last edited by GordonR_Cape; 24th Apr 2019 at 07:58.
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Old 24th Apr 2019, 08:22
  #4263 (permalink)  
 
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Thanks for that. It does sound rather counter-intuitive that as soon as AoA drops below the threshold for MCAS commanding AND trim, it then does the opposite.

I note that the extract from the Max System Differences Training Manual (presumably a Boeing publication) on Chris's site makes no mention of MCAS commanding ANU trim:



http://www.b737.org.uk/images/mcas-mtm.jpg
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Old 24th Apr 2019, 08:52
  #4264 (permalink)  
 
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Originally Posted by DaveReidUK View Post
Thanks for that. It does sound rather counter-intuitive that as soon as AoA drops below the threshold for MCAS commanding AND trim, it then does the opposite.

I note that the extract from the Max System Differences Training Manual (presumably a Boeing publication) on Chris's site makes no mention of MCAS commanding ANU trim:
Yes, several people (including myself) have pointed out that definition leads to an "unstable" outcome when AOA fluctuates close to the 10 degree threshold. Not an elegant algorithm at all...
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Old 24th Apr 2019, 09:56
  #4265 (permalink)  
 
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Originally Posted by GordonR_Cape View Post
I can't find primary references stating that, other than the text and chart by LEOCh previously mentioned: https://www.pprune.org/showthread.php?p=10423226

The best simple description is a single sentence from b737.org.uk: 737 MAX - MCAS
The description cited above is not an official Boeing source. I have seen not any system description from Boeing that states that MCAS will ever input nose up trim. In this way, it is not unlike what the Speed Trim System does approaching a stall when the flaps are extended.
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Old 24th Apr 2019, 10:16
  #4266 (permalink)  
 
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Originally Posted by 737 Driver View Post


The description cited above is not an official Boeing source. I have seen not any system description from Boeing that states that MCAS will ever input nose up trim. In this way, it is not unlike what the Speed Trim System does approaching a stall when the flaps are extended.
The more that comes out - the simple power and pitch pilots will save the day, seems less likely as hidden automation seems to kill those egos.

MCAS version 1 had big problems - version 2 has the same but different problems.

Just recall guys no, or low MCAS input = possible flight outside certification limits within the flight envelope is possible. Thus pitch and power is not relevant as it is not proven and unless you are a Test Pilot commenting on 737 flight outside the certification limits is no more relevant than a pax.

Clearly even today MCAS is not understood and there seem many secrets - that should have never been the case. But it seems to be the future.
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Old 24th Apr 2019, 10:51
  #4267 (permalink)  
 
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Originally Posted by 737 Driver View Post


The description cited above is not an official Boeing source. I have seen not any system description from Boeing that states that MCAS will ever input nose up trim. In this way, it is not unlike what the Speed Trim System does approaching a stall when the flaps are extended.
Correct, but there are multiple credible sources saying effectively the same thing. It was in point (1) of FCEng84's long clarification post earlier in thread: link

FCEng84 has posted good, readable, and apparently accurate information on MCAS from the start, I haven't had reason to dispute any of the other information so I would tend to trust this part too.

Last edited by infrequentflyer789; 24th Apr 2019 at 17:10. Reason: Fixed broken link
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Old 24th Apr 2019, 11:33
  #4268 (permalink)  
 
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Originally Posted by DaveReidUK View Post
Thanks for that. It does sound rather counter-intuitive that as soon as AoA drops below the threshold for MCAS commanding AND trim, it then does the opposite.

I note that the extract from the Max System Differences Training Manual (presumably a Boeing publication) on Chris's site makes no mention of MCAS commanding ANU trim:



http://www.b737.org.uk/images/mcas-mtm.jpg
The training guide quoted states of MCAS that it ďallows the stabiliser to move in the nose down direction etc.Ē It does more than allow if it causes it to move...
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Old 24th Apr 2019, 12:11
  #4269 (permalink)  
 
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Originally Posted by edmundronald View Post

Interestingly, on this forum, pilots seem to blame the Max pilots for not flying their planes, while engineers blame the design and the process. Quite possibly both are correct.

Edmund
There are a handful of skygods on here who continuously say "they should have" or "all they needed to do was" or "I would have just" and so on.

In my opinion, pilots with these outlooks are less than safe.

They have a high opinion of themselves.
They have not appreciated the HF elements of these accidents.
They have not considered how HF will affect their operation, in the event of a serious problem.
They are therefore not prepared.

If we just blame the pilots for being a bit crap, then nothing in the industry will improve. We need to understand why these pilots, despite all of their efforts, could not keep the aircraft from the ground. Only when we understand, can we make the correct changes to stop it happening again.

Even the finest pilots in the world, when suddenly presented with a simple failure (double engine failure, for example), will sit there and think "no - this can't be happening" followed by "what on earth do I do".

It is inexcusable that Boeing and the FAA allowed a pretty ropy old aircraft with some dodgy characteristics to be released with even poorer characteristics. It is a demonstration of how multiple signals during a critical phase of flight can make it very difficult for pilots to overcome startle, then diagnose, fly and solve a problem.

As an aside - in my airline it was discovered that UAS events were handled badly. So in one sim cycle we were trained. In the next sim cycle we were tested, and still it was handled badly. So in the next sim cycle again we were trained a lot more. It transpires that real UAS is really a HF event of great complexity, and is therefore very difficult to get right. The technical side of it is a doddle.

Can we please focus on how we contribute to make the industry better (safer)?


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Old 24th Apr 2019, 12:14
  #4270 (permalink)  
 
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There have been plenty of other cases of commercial airline instrument failures leading to unexpected system responses and confusion among the crew. You just donít hear about them because these events had a successful conclusion.

That's a diversionary response. This was not just a case of "unexpected system responses". MCAS commandeered the most powerful control surface on the airplane and, in effect, caused an intermittent runaway, something for which nobody was trained.
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Old 24th Apr 2019, 12:22
  #4271 (permalink)  
 
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Originally Posted by 737 Driver View Post
The description cited above is not an official Boeing source. I have seen not any system description from Boeing that states that MCAS will ever input nose up trim. In this way, it is not unlike what the Speed Trim System does approaching a stall when the flaps are extended.
I understand that, and cannot find an official Boeing source. But think about this scenario for one minute:
An "undocumented" maneuver augmentation system that leaves the nose trim 2.5 degrees lower than when it started.
Do you think Boeing would ever release that?
Do you think the FAA would ever certify that?
Logic dictates that your version makes no sense, for a feature which everyone agrees is not an anti-stall system.
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Old 24th Apr 2019, 12:58
  #4272 (permalink)  
 
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I would say the MCAS trim must be reset to the original place to comply with the certification requirements. When control force is released the airspeed must return to within a small percentage of the original trim speed and also a push on the column be needed to achieve a speed below that original trim speed.
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Old 24th Apr 2019, 13:25
  #4273 (permalink)  
 
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Most incidents are resolved OK but here are three other crashes where the published cause seems questionable.

https://en.wikipedia.org/wiki/Kenya_...#Investigation

https://en.wikipedia.org/wiki/Ethiop...nes_Flight_409

https://en.wikipedia.org/wiki/EgyptAir_Flight_990

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Old 24th Apr 2019, 14:01
  #4274 (permalink)  
 
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Originally Posted by HundredPercentPlease View Post
There are a handful of skygods on here who continuously say "they should have" or "all they needed to do was" or "I would have just" and so on.

In my opinion, pilots with these outlooks are less than safe.

They have a high opinion of themselves.
They have not appreciated the HF elements of these accidents.
They have not considered how HF will affect their operation, in the event of a serious problem.
They are therefore not prepared.

If we just blame the pilots for being a bit crap, then nothing in the industry will improve. We need to understand why these pilots, despite all of their efforts, could not keep the aircraft from the ground. Only when we understand, can we make the correct changes to stop it happening again.

Even the finest pilots in the world, when suddenly presented with a simple failure (double engine failure, for example), will sit there and think "no - this can't be happening" followed by "what on earth do I do".

It is inexcusable that Boeing and the FAA allowed a pretty ropy old aircraft with some dodgy characteristics to be released with even poorer characteristics. It is a demonstration of how multiple signals during a critical phase of flight can make it very difficult for pilots to overcome startle, then diagnose, fly and solve a problem.

As an aside - in my airline it was discovered that UAS events were handled badly. So in one sim cycle we were trained. In the next sim cycle we were tested, and still it was handled badly. So in the next sim cycle again we were trained a lot more. It transpires that real UAS is really a HF event of great complexity, and is therefore very difficult to get right. The technical side of it is a doddle.

Can we please focus on how we contribute to make the industry better (safer)?
Well said, totally agree
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Old 24th Apr 2019, 14:29
  #4275 (permalink)  
 
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Fly the damn aircraft

Originally Posted by edmundronald View Post
Interestingly, on this forum, pilots seem to blame the Max pilots for not flying their planes, while engineers blame the design and the process. Quite possibly both are correct.
You are correct, sir.

Aircraft accidents are rarely the result of a single cause. In this case, we have a failure in the initial design process, a failure in the internal (Boeing) review process, a failure in the oversight process (FAA and other certifications authorities), a failure in the education and training process (airlines, Boeing, certifications authorities), and at least one documented failure in the maintenance process (Lion Air). However, despite all these numerous failures, the aircraft in question were still flyable by reverting to basic airmanship techniques of pitch, power, and trim. Yet here we are.

I am not an engineer, so I donít have the background to say exactly how the engineers went wrong, even though I know they did. I am not a project manager or regulator, so I donít have the expertise to say exactly how they erred. I am not a maintenance technician, so I am not qualified to comment on where their process went wrong. Iím a little closer to the airline training environment, so I feel I can comment on how they could have handled this better.

However, I most certainly am a 737 type-rated Captain who is given the responsibility of saving the lives of my passengers when everyone else fails to do their job. Even at my airline, our training should be better, our manuals should be better, our maintenance procedures should be better, and our scheduling practices should be better, but the reality is that they are not. I do not have the leisure to say that if all these other people donít do their job right, I donít have to do mine. My job, when everything goes to $hit, is to do everything in my power to stabilize the aircraft and get it safely back on the ground. If I donít, then that is on me.
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Old 24th Apr 2019, 14:39
  #4276 (permalink)  
 
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Originally Posted by GordonR_Cape View Post
I understand that, and cannot find an official Boeing source. But think about this scenario for one minute:
An "undocumented" maneuver augmentation system that leaves the nose trim 2.5 degrees lower than when it started.
Do you think Boeing would ever release that?
Do you think the FAA would ever certify that?
Logic dictates that your version makes no sense, for a feature which everyone agrees is not an anti-stall system.
I’m not trying to argue logic or whatever Boeing and FAA should have done. Obviously, the MCAS design was flawed. I am simply reporting what has been officially stated about how this system actually works.

For non-pilots, it may be difficult to relate to the dynamic environment of an approach to stall and recovery maneuver. The going in assumption is that the pilots would not intentionally place the aircraft close to the stall. When an approach to stall is detected, various aircraft systems kick in to both provide warning and assistance. However, it is also assumed that once alerted to the stall, the pilots will disengage the automation and hand-fly the aircraft back to a safe airspeed and altitude. This maneuver involves the same things I keep referring to - pitch, power, and trim. I can only speak for the aircraft I have flown, and not a single one of them was designed for the automation to execute the stall recovery. Assist, yes. Execute, no.

Last edited by 737 Driver; 24th Apr 2019 at 14:42. Reason: clarity
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Old 24th Apr 2019, 14:42
  #4277 (permalink)  
 
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Originally Posted by 737 Driver View Post


You are correct, sir.

Aircraft accidents are rarely the result of a single cause. In this case, we have a failure in the initial design process, a failure in the internal (Boeing) review process, a failure in the oversight process (FAA and other certifications authorities), a failure in the education and training process (airlines, Boeing, certifications authorities), and at least one documented failure in the maintenance process (Lion Air). However, despite all these numerous failures, the aircraft in question were still flyable by reverting to basic airmanship techniques of pitch, power, and trim. Yet here we are.

I am not an engineer, so I donít have the background to say exactly how the engineers went wrong, even though I know they did. I am not a project manager or regulator, so I donít have the expertise to say exactly how they erred. I am not a maintenance technician, so I am not qualified to comment on where their process went wrong. Iím a little closer to the airline training environment, so I feel I can comment on how they could have handled this better.

However, I most certainly am a 737 type-rated Captain who is given the responsibility of saving the lives of my passengers when everyone else fails to do their job. Even at my airline, our training should be better, our manuals should be better, our maintenance procedures should be better, and our scheduling practices should be better, but the reality is that they are not. I do not have the leisure to say that if all these other people donít do their job right, I donít have to do mine. My job, when everything goes to $hit, is to do everything in my power to stabilize the aircraft and get it safely back on the ground. If I donít, then that is on me.
As I'm sure the Lion Air and Ethiopian pilots did ! None of them wanted to die. None of them gave up until hitting the ground. So, what is your point ??
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Old 24th Apr 2019, 15:00
  #4278 (permalink)  
 
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I think the point (presumably) he is trying to make is that he would not have crashed due to superior flying skill. Basically rubbish of course.
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Old 24th Apr 2019, 15:11
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Even the finest pilots in the world, when suddenly presented with a simple failure (double engine failure, for example), will sit there and think "no - this can't be happening" followed by "what on earth do I do".
Half right in the case of Cactus 1549. 'The physiological reaction was strong and I had to use training to force calm on the situation. I was sure I could do it' said Capt Sullenberger.

The 'finest pilots in the world' are probably amongst the best trained pilots in the world. Good training undoubtedly makes a difference to outcomes.
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Old 24th Apr 2019, 15:26
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Originally Posted by MD80767 Driver View Post
As I'm sure the Lion Air and Ethiopian pilots did ! None of them wanted to die. None of them gave up until hitting the ground. So, what is your point ??
Is it also your position that the engineers did everything they could do? The MAX program managers? Boeing? The regulators? The airlines and their training departments? Did all these people simply meet expectations? Do we just sit idly by and say, “That’s okay, I’m sure you did your best” ?!

The responsibility for these accidents should be shared broadly, but the pilots are almost always the first ones to the scene of the accident. Sometimes we cannot simply accept a certain level of training and skills because we passed the minimum standards of a training department whose primary allegiance is to an organization that wants to keep the metal moving at a minimum cost.

The point is to learn not only from our mistakes, but also the mistakes of others. No, I don’t think anyone intended for hundreds of people to die, but die they did. Every specialty that touched these accidents ought to be doing a lot of soul searching and asking themselves how they could have done better.

As far as the flight crew, no one was expecting them to come up with some innovative split-s, half-barrel roll maneuver to save this aircraft. All that was required of the flying pilot was to recognize the immediate problem, execute the first steps of what should have been a well-known procedure, keep his thumb near the yoke trim switch, and simply trim the stab as necessary. Turn off the magic, pitch 10 degrees, power to 80% and trim. That's it! This is not test pilot territory.

Have our expectations of what constitutes basic airmanship skills for a commercial airline pilot fallen so low?

Last edited by 737 Driver; 25th Apr 2019 at 01:07. Reason: Typo, added comment
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