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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 3rd May 2019, 10:56
  #4781 (permalink)  
 
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@SystemsNerd
One possible solution (on which there is probably a bunch of research that may show it to be a very poor idea) would be to hook crews up to an IV line in sim training, and give them a massive slug of adrenaline when they first realise something is wrong. Their body is then going to want to drop into a classic fight-or-flight response; given that a stall can neither be run away from nor punched to death, this is unproductive, so you'd want to train pilots to manage this physiological process so they can get back to applying their rational-mind training as quickly as possible, and fly the damn plane. If they don't have this training, it's not surprising that they're failing at this in real life, and if that's the case then all the sim time and process-knowledge in the world isn't going to save them.
That kind of intensive training was used for early astronauts (The Right Stuff), since the risks were very high, but the dropout rate was very high. Some of today's veteran pilots with military fast-jet experience, might also have gone through that process. In the current era of widespread passenger jet transportation, I don't think that kind of training is viable.
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Old 3rd May 2019, 11:55
  #4782 (permalink)  
 
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Originally Posted by CurtainTwitcher View Post
In the isolation of a simulator session where the sim instructor selects a runaway trim malfunction, fully agree with you.

Press play below before reading on...

https://youtu.be/TrjTUvhpBlE

This was not a classic runaway trim. No trim issues were encountered until the flaps were retracted. Retract flaps, now some forward trim starts, trim back with the electric trim and everything is good for 5 seconds, just enough time to start thinking about else, there goes the trim again, fix it with electric trim, all good for 5 seconds, repeat until end of sequence. You are also dealing with an airspeed unreliable. Not easy with that racket going on the background.

To the pilots in all three event flights, this was a trim fight, not a continuous runaway in the QRH condition statement for a Runaway Stabilizer. Judge for yourself from a current in-service document:

Condition: Uncommanded stabilizer trim occurs continuously
The trim worked as they expected, sort of. If English was not your first language, it would be even more difficult.

The Lion Air crews were in the worst position, they had no prior knowledge of the subtle system changes and faults that had led them to trim fight, not a runaway.

Originally Posted by L39 Guy View Post


Runaway Stabilizer: Uncommanded stabilizer trim movement occurs continuously. (Source B737 NNC)



In November 2018, after Lion Air, some (or all) operators, changed the checklist list and removed the word “continuous”.
























Last edited by Lost in Saigon; 3rd May 2019 at 12:40.
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Old 3rd May 2019, 12:05
  #4783 (permalink)  
 
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Hard to keep up ...

But this comes from the Wall Street Journal:

Boeing test pilots lacked key details of 737 MAX flight-control system

Boeing limited the role of its own pilots in the final stages of developing the 737 MAX flight-control system implicated in two fatal crashes, departing from a longstanding practice of seeking their detailed input, people familiar with the matter said.


As a result, Boeing test pilots and senior pilots involved in the MAX’s development didn’t receive detailed briefings about how fast or steeply the automated system known as MCAS could push down a plane’s nose, these people said.
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Old 3rd May 2019, 12:25
  #4784 (permalink)  
 
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Originally Posted by A0283 View Post
Hard to keep up ...

But this comes from the Wall Street Journal:

Boeing test pilots lacked key details of 737 MAX flight-control system Boeing limited the role of its own pilots in the final stages of developing the 737 MAX flight-control system implicated in two fatal crashes, departing from a longstanding practice of seeking their detailed input, people familiar with the matter said.

As a result, Boeing test pilots and senior pilots involved in the MAX’s development didn’t receive detailed briefings about how fast or steeply the automated system known as MCAS could push down a plane’s nose, these people said.
I already posted this article link in one of the parallel threads, and since the overall story is quite profound. Even though most of the information is not new, it is worth skimming, to be reminded of some of the details: https://www.theverge.com/2019/5/2/18...error-mcas-faa

Summary:
- Mistakes began nearly a decade ago when Boeing was caught flat-footed after its archrival Airbus announced a new fuel-efficient plane that threatened the company’s core business. It rushed the competing 737 Max to market as quickly as possible.
- In developing the Max, Boeing not only cut corners, but it touted them as selling points for airlines. Since the 737 Max was the same plane type as its predecessors, pilots would only need a 2.5-hour iPad training to fly its newest iteration.
- MCAS is the new software system blamed for the deadly Lion Air and Ethiopian Airlines crashes. But its failure in both crashes was the result of Boeing and the Federal Aviation Administration’s reluctance to properly inform pilots of its existence or to regulate it for safety.
- The FAA has admitted to being incompetent when regulating software, and, as a policy, it allows plane manufacturers to police themselves for safety. Nowhere in its amended type certification of the 737 Max is MCAS mentioned.
- Even still, Boeing only recommends a 30-minute self-study course for pilots on MCAS, rather than additional simulator or classroom instruction.
- Despite the two crashes, neither Boeing nor the FAA believes they’ve done anything wrong. A Boeing spokesperson said the company believes the system is still “a robust and effective way for the FAA to execute its oversight of safety.”
Nothing specific to test pilots, but these comments are telling:
And many pilots felt that, for the first new 737 in over 20 years, Boeing seemed to be oddly reluctant to prep them for it.

Captain Laura Einsetler, who’s flown for over 30 years, including on 737s, considers an all-computer-based course to be completely inadequate as an introduction to a new airplane.

“I don’t have the schematics. I don’t have the cockpit panels. I don’t have an instructor that I can ask questions to,” she says. “You’re hoping that the first time you see the Max is on a nice clear day. But sometimes it’s not, and you’re showing up at night or in bad weather into an airplane that has all these changes.”
The subtext: pilots were on a need-to-know basis about MCAS, and until the Lion Air crash, Boeing felt that they hadn’t needed to know.

Einsetler strongly disagrees. “We need to have the understanding and knowledge of how everything works on the jet, so that we can command the jet to do what we need it to do, not just be along for the ride,” she says.

“Not a lot of information got out there in a timely fashion,” concurs Juan Browne, a 777 pilot with over 40 years of flying experience. “It almost makes me wonder, did Boeing engineers themselves really understand how much power and authority they built into this system?”
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Old 3rd May 2019, 12:40
  #4785 (permalink)  
 
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Originally Posted by robocoder View Post

Quote:
Originally Posted by SystemsNerd Thus, when asking "why didn't they just fly the plane?", one possible answer is undoubtedly some variant on "they were incompetent". But another possible answer is "they were put into a scenario in which any human being would consistently fail to solve the problem, regardless of competence". Probably the truth is somewhere between those two points.
​​​​​​Thank you so much for this This is why I cannot accept the analysis of those that pile with unwavering assertiveness on the pilots' performance. We have only a partial view of what they experienced. We simply cannot know what the average crew would do in their shoes, vs what some hypothetical post-hoc average response should be, as evident as it may seem. Even so, are they at fault for the training they received? That's why when someone can't come back to tell their version, I prefer unanswered questions to "sure" answers.
As stated by SystemsNerd, the human cognition has limitations and foibles that many people are unaware of. One of these is the limited number of 'cognitive channels' also known as multiple resource theory. (see papers by Christopher Wickens and Erik Hollnagel) Simply you cannot read this posting and recite a something you have learned like NNC memory items at the same time - both use verbal cognition - if you are reading and someone says something you may hear them but you will not understand what they said and you will stop reading and ask them to repeat what they said. If you have to read, talk and listen at the same time you can only really do one at a time (we have all had to read a paragraph again as we stopped understanding what we were reading and listened instead).
So if you are running through memory items of an NNC - and you read the EICAS you may miss NNC items or not understand the EICAS - if the PM is shouting at you it may just be noise - if there is sufficient noise that channel stops completely and you do not even hear/comprehend the PM or that cavalry charge.

Mixed into this is the effect of the level of stress/alertness. This is normally referred to as an 'inverted U'.


from MindTools.com

So when you are bored with low stress your performance is actually poor, A little pressure / stress and your performance is ideal, but too much high stress and your performance will drop off rapidly.

Putting all that into an aviation perspective, A well trained pilot with experience of things going pear shaped and operating under pressure will not feel so much stress and concentrate on one item at a time and a lot of what will be done will be (what is called here ) muscle memory - innate training like stamping on a brake or steering a bike to stay balanced - or trimming an aircraft - it requires no thought as it is second nature. This is the importance of training - with not so much training it is easy to get into the overstressed very low performance state and 'get behind the aircraft'. The more inputs you are given the higher the stress and the less you are able to process and the normal human reaction to that is what is known as attentional or cognitive tunneling - a concentration on one aspect of what is happening that you _do_ think you can control and a total disregard of anything else. Everyone is different in this regard and the only way to avoid getting into the wrong side of the U is training, repeated training to get that muscle memory. Unfortunately, there is always a beancounter standing in the way of that.
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Old 3rd May 2019, 12:54
  #4786 (permalink)  
 
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Yo gums,
Further to my comments on your additional request for ‘aero’ explanation ( Ethiopian airliner down in Africa) see the following:-

During design of the MAX, Boeing added two more leading-edge vortilons [generating vortices over the top of the wing at high AOA] in 2018, for a total of six per side and also lengthened and raised the inboard leading-edge stall strips to assure stall behavior would be as docile as that of the NG.
(https://www.twu557.org/index.php/new...x-new-software)

This suggests that Boeing had identified issues earlier than I suggested; also because of the nature of the changes the aero effects were more significant than currently being discussed for MCAS.
The use of vortilons might be a simple alternative to adding many more vortex generators, but stall strips to reinforce the inner-wing stall before outboard sections, opposing pitch up, is more like ‘a new aircraft’ fix.
A very crude comparison of the effects of nacelle lift might be made with military blended wing / fuselage, or leading edge extensions; what ever these provide for the fighter world then its not helpful in commercial aviation - or at least a same type rating for the 737 MAX.

Also, Boeing ‘Commenting on criticism of the single string failure potential of the AOA input to MCAS, a Boeing official said the original design was based on a standard industry process of hazard classification which defined the potential failure as one that could be mitigated “very quickly performed by a trained pilot using established procedures”.

Add to that, a remarkable comment from the FAA; “Pilots of large aircraft are trained from Day 1. When the pitch of the aircraft is doing something you’re not telling it to do, you do a runaway pitch trim checklist,” Acting FAA Administrator Dan Elwell, a former airline pilot …
This does not add confidence that the FAA have a good understanding of training, nor the much wider safety aspects of loss of control (for wind-shear / turbulence pitch up - do we always inhibit trim ! )
https://www.twu557.org/index.php/new...-human-factors

Then re the training discussion:-
Pilots for three U.S. air carriers tell … that during their sim training they had never been exposed to extreme and continuous AOA indication errors, they’ve not experienced AOA induced airspeed and altitude deviations on PFDs and have not had to deal with continuous stall-warning stickshaker distractions. They also note that they have never been required to fly the aircraft from the point at which a runaway stab trim incident occurred all the way to landing using only the manual trim wheels. “We’re just checking boxes for the FAA,” says one Seattle-based pilot’.

P.S. some web links may be transposed, or changed by the host site - search news items (I’m working on it).

Last edited by PEI_3721; 3rd May 2019 at 13:01. Reason: P.S.
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Old 3rd May 2019, 13:02
  #4787 (permalink)  
 
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Originally Posted by 737 Driver


I have no doubt that this is true, but it is also largely irrelevant from a procedural viewpoint. The pilots don’t need to be able to read a wiring diagram and tell you all the things that happens when they throw the cutout switches. They just need to know when they need to throw the cutout switches - as in the case of the runaway stab trim procedure.


737 driver, I have an itch and please take this comment with the best of intent.

When I was taught to fly, PPL through CPL etc, it was instilled in me to understand what every switch/knob did before I played with it (initial thanks to Norman Buddin, ex Hunter pilot and CFI). We were not in the business of altering things without understanding the impact.

So, please correct me if I am wrong, but earlier versions of the 737 had two distinct outcomes associated with the two stab trim switches whilst the Max basically has two switches in series? Somewhere along the line a change operating procedures seem to have pre-dated the wiring change. I’m trying to understand why pre-Max pilots didn’t know, or weren’t told about, the difference between the switches. Isn’t it better airmanship to understand why, what and how when managing aircraft systems, or are we witness to the pre-cursor of ‘Children of the Magenta’ in pilots who never questioned why they threw two switches and what each did?





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Old 3rd May 2019, 13:17
  #4788 (permalink)  
 
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"In November 2018, after Lion Air, some (or all) operators, changed the checklist list and removed the word “continuous”."

"
By this definition, isn't any STS operation a trim runaway? "

Pilots of large aircraft are trained from Day 1. When the pitch of the aircraft is doing something you’re not telling it to do, you do a runaway pitch trim checklist,” Acting FAA Administrator Dan Elwell, a former airline pilot …"

Cool. Looks like we're finally going to get my F/Os some experience in using the manual trim wheel.

Originally Posted by Cows getting bigger View Post

When I was taught to fly, PPL through CPL etc, it was instilled in me to understand what every switch/knob did before I played with it (initial thanks to Norman Buddin, ex Hunter pilot and CFI). We were not in the business of altering things without understanding the impact.

Cows Getting Bigger (best username ever!), I agree with you 100%...and would add my thanks to Swede Gamble ("Know Gamble in Aviation").
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Old 3rd May 2019, 13:19
  #4789 (permalink)  
 
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Originally Posted by Dave Therhino View Post
MCAS can be interrupted with the electric trim switches on the yoke each time it activates, and trim can be returned to a low/zero column force state each time if the pilot puts in adequate opposite trim inputs. That is what the Lion Air crew did for approximately 2 dozen cycles of MCAS before the final few cycles, where the pilot flying at that point failed to put in an adequate amount of opposite trim in those final cycles, allowing the out of trim condition to increase to the point where they couldn't recover in the altitude available.
That is the assumption that is at question (my emphasis). If your suggestion is correct then the crew did not apply sufficient opposite trim inputs. It remains in doubt as to whether it is possible to apply sufficient opposite trim inputs. If Boeing is to be believed the Lion Air pilots casually flew the aircraft into the sea and did not attempt to apply sufficient opposite trim inputs. I do not buy into this theory. I suspect that the only solution is to use the cutout switches at an early stage. There may be multiple reasons that sufficient opposite trim is not possible. What is raising doubt is that the Lion Air pilots were trying to do just what you suggest and did not succeed. Granted, that they should have taken a different path, but it remains they were trying to trim nose-up and apparently were unable. There is a lot more to this story, I suspect that many assumptions being made are not entirely correct. People are trying to reverse engineer from Boeing publications that may not be entirely accurate and are too brief to give a full explanation of the systems. So far it does not seem to make sense. I could be wrong, but my bullshit meter is quivering.
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Old 3rd May 2019, 13:26
  #4790 (permalink)  
 
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@PEI_3721 - I was looking at a MAX video and noticed, next to the usual big strake at about 10 o'clock on the center of the cowling, a set of 2 smaller longitudinal white painted vanes/strakes on the inside of the engine on the sliding part of the thrustreversers. When the reversers slid back after TD, the vanes/strakes did not hit the leading edge of the wing, because a kind of small 'trapdoor' opened upward to let them pass through. On sliding forward the vanes/strakes became visible again and the 'trapdoor' closed behind them. Would be interesting to hear from you what their purpose is in the aerodynamic context that you were just posting about ;-)
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Old 3rd May 2019, 13:27
  #4791 (permalink)  
 
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Originally Posted by L39 Guy View Post

Yes, the overhead panel is 1960’s but the cockpit displays, FMS, engines, wings, and other major components sure aren’t. The point is not a part by part count but the major components of the MAX are completely different than the -100 even to the extent that one could legitimately not call it a B737.
Yes but it's still an old generation design with old generation aircraft failings.
No EICAS , no FBW (with resultant large pitch /power couple, defo not good news on manual go arounds), only two hydraulic systems, no effective autopilot go around (Cat3 excepted) etc etc, not even auto generator switching!
Most of the design changes apart from maybe the nice big screens seem to be all about economic improvements, not safety improvements, ie thinner more efficient but less speed stable wing, longer fuselage with resultant higher approach speed to prevent tail strikes on landing.
I could list more, it's a real shame they didn't build a new modern aircraft from the ground up (like the 777/787) but that would have really hit profits in the short term, I'm sure Boeing wish they had now.
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Old 3rd May 2019, 13:31
  #4792 (permalink)  
 
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Originally Posted by SystemsNerd View Post
With respect, I think there may be a breakdown in communication here that may be in large part responsible for the ongoing disagreement. When people say "human factors", they don't mean "the human element", they mean Human Factors*, i.e., the study of how the human mind and body interacts with designed systems.

The human mind does not, ironically, work in the ways most people think it does - it has well-documented limitations and sources of error plumbed into its design. A human factors expert can I believe pretty trivially design a scenario where most (if not all) humans will consistently fail to correctly solve even relatively trivial problems, regardless of their competence under normal conditions.

Thus, when asking "why didn't they just fly the plane?", one possible answer is undoubtedly some variant on "they were incompetent". But another possible answer is "they were put into a scenario in which any human being would consistently fail to solve the problem, regardless of competence". Probably the truth is somewhere between those two points.
I pretty much agree with everything you say except for the "any human" reference in the second to last sentence. I think that there is broad, though not unanimous, agreement that the accident crews made some serious errors that led to the final loss of aircraft control. Where I and some other participants here differ is that I strongly believe that much of the human factors element you refer to is amenable to training. One only has to look at the performance of the crew on the Lion Air 610 flight the day prior to the original accident. Despite being presented with a novel malfunction, one of the pilots kept flying the aircraft. IMHO, that crew took a bit too long to get to the trim cutout switches, but the takeaway is that every time MCAS made an input, the flying pilot took it right out again. At no time was there evidence that they were losing that fight.

It has been suggested that this crew would have ultimately crashed if not for the jumpseater suggesting that they try the cutout switches, but frankly that is an unwarranted assumption. Having been both in the flying seat and the jumpseat on many occasions, it is absolutely true that the jumpseater may catch something quicker, but that does not mean the flying crew will not catch it at all. There definitely appears to been a limited understanding of the stab trim system by both the Lion Air and Ethiopian crews (very much amenable to training), but it did not prevent the crew above from maintaining aircraft control.

I will agree that any human pilot at some stage in their training will be easily overwhelmed by even the most basic aircraft emergency scenarios. That is why we train so extensively for them. I had previously posted that in the Ethiopian accident, the Captain did fly the aircraft after a certain fashion, and that he had defaulted to his training. The problem was that he defaulted to the wrong training. Just about all of the ET302 Captain's initial actions can be understood in the context of a normal takeoff profile. Unfortunately, a normal takeoff profile left him in a highly unstable position from which dealing with the ultimate stab trim problem became a bridge too far.

When I and other posters keep saying that the pilots should have kept FLYING THE AIRCRAFT, we do not say this from a perspective that operating a malfunctioning aircraft is some inborn capability that every person has. Heck, walking isn't even an inborn capability. However, it is a skill that is amenable to training. That is, as long as you get the right kind of training. As has been already discussed extensively, training in modern commercial airliners has largely devolved into a process of following scripts. Pilots are presented with known problems with known solutions. Even at my airline, there is much less of the relatively unscripted training that really drove home the need to set aside any distractions and focus on the basics of flying the aircraft without the benefit of any automation until the situation was stabilized.

There are multiple links in the chain of causation leading to these accidents. I don't think anyone is questioning that MCAS needs to be fixed, or the FAA needs to step up its oversight, or that airlines need to review their internal training and operations policies. The professional pilot corps, however, needs to look at what we can do to correct the airmanship deficiencies that were exposed by these accidents.

Last edited by 737 Driver; 3rd May 2019 at 17:40.
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Old 3rd May 2019, 13:38
  #4793 (permalink)  
 
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Originally Posted by A0283 View Post
I was looking at a MAX video and noticed, next to the usual big strake at about 10 o'clock on the center of the cowling, a set of 2 smaller longitudinal white painted vanes/strakes on the inside of the engine on the sliding part of the thrustreversers. When the reversers slid back after TD, the vanes/strakes did not hit the leading edge of the wing, because a kind of small 'trapdoor' opened upward to let them pass through. On sliding forward the vanes/strakes became visible again and the 'trapdoor' closed behind them. Would be interesting to hear from you what their purpose is in the aerodynamic context that you were just posting about ;-)
It's not aerodynamics, its just a physical way to keep the reverser sliding cowl from hitting the leading edge devices...been there since the Classics.
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Old 3rd May 2019, 13:45
  #4794 (permalink)  
 
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A0283,
Simple answer, I don’t know.
I’m looking for photos - found (Aerospaceweb.org | Ask Us - Nacelle Vortex Generator), but as you describe this does not fit my experience with vortilons - underwing leading edge with sharp/ pointy bits protruding forward. Nor any experience with engine cowl / nacelle strikes, attachments, bent metal, etc (my ‘jet’ although using stall breakers and stick push, had no vortex generators or other aero adjustments at all - match that).

https://en.m.wikipedia.org/wiki/Vortilon

Aerospaceweb.org | Ask Us - Wing Vortex Devices

Takwis -I doubt your explanation; see photo above


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Old 3rd May 2019, 13:50
  #4795 (permalink)  
 
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@Takwis - Thanks for responding . So no aerodynamic impact. Solved. @PEI_3721 thanks for your time.

Edit1: After PEI's response to Takwis's post I tried to dig up one of my images to put us on a level 'playing field'.


A0283

Edit2: In PEi's http://www.aerospaceweb.org/question...cs/q0255.shtml the dual strakes are visible on its 1st photo. The article says the big strake is on the -600 upto -900.

@Takwis - Could you tell me what the names of the big strake, the small strips, and the trapdoor are in 'Boeing speak'.

Last edited by A0283; 3rd May 2019 at 14:48. Reason: Adding photo after PEI's response to Takwis and two more edits
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Old 3rd May 2019, 14:02
  #4796 (permalink)  
 
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Originally Posted by 737 Driver View Post
I pretty much agree with everything you say except for the "any human" reference in the second to last sentence. I think that there is broad, though not unanimous, agreement that the accident crews made some serious errors that led to the final loss of aircraft control. Where I and some other participants here differ is that I strongly believe that much of the human factors element you refer to is amenable to training. One only has to look at the performance of the crew on the Lion Air 610 flight the day prior to the original accident. Despite being presented with a novel malfunction, one of the pilots kept flying the aircraft. IMHO, that crew took a bit too long to get to the trim cutout switches, but the takeaway is that every time MCAS made an input, the flying pilot took it right out again. At no time was there evidence that they were losing that fight.

It has been suggested that this crew would have ultimately crashed if not for the jumpseater suggesting that they try the cutout switches, but frankly that is an unwarranted assumption. Having been both in the flying seat and the jumpseat on many occasions, it is absolutely true that the jumpseater may catch something quicker, but that does not mean the flying crew will not catch it at all. There definitely appears to been a limited understanding of the stab trim system by both the Lion Air and Ethiopian crews (very much amenable to training), but it did not prevent the crew above from maintaining aircraft control.

I will agree that any human pilot at some stage in his training will be easily overwhelmed by even the most basic aircraft emergency scenarios. That is why we train so extensively for them. I had previously posted that in the Ethiopian accident, the Captain did fly the aircraft after a certain fashion, and that he had defaulted to his training. The problem was that he defaulted to the wrong training. Just about all of the ET302 Captain's initial actions can be understood in the context of a normal takeoff profile. Unfortunately, a normal takeoff profile left him in a highly unstable position from which dealing with the ultimate stab trim problem became a bridge too far.

When I and other posters keep saying that the pilots should have kept FLYING THE AIRCRAFT, we do not say this from a perspective that operating a malfunctioning aircraft is some inborn capability that every person has. Heck, walking isn't even an inborn capability. However, it is a skill that is amenable to training. That is, as long as you get the right kind of training. As has been already discussed extensively, training in modern commercial airliners has largely devolved into a process of following scripts. Pilots are presented with known problems with known solutions. Even at my airline, there is much less of the relatively unscripted training that really drove home the need to set aside any distractions and focus on the basics of flying the aircraft without the benefit of any automation until the situation was stabilized.

There are multiple links in the chain of causation leading to these accidents. I don't think anyone is questioning that MCAS needs to be fixed, or the FAA needs to step up its oversights, or that airlines need to review their internal training and operations policies. The professional pilot corps, however, needs to look at what we can do to correct the airmanship deficiencies that were exposed by these accident.
When you say that you "strongly believe" the issue is amenable to training, is that based on research or on intuition? I ask because my understanding of the broad sweep of behavioural research is that actual human behaviour is often deeply unintuitive, and in a safety-critical environment I'd be very wary of relying on any assumptions about human behaviour that haven't been rigorously validated.

(I fully agree that pilots need to do their part in correcting any systemic errors contributing to these incidents; my concern is that treating them as "human error" or "poor training" passes up an opportunity to better understand how and why people actually make mistakes, and how to avoid falling into the same traps. Like, I read wonkazoo's underlying point about his crash as being "I knew exactly what to do and I *still* almost killed myself, because a real incident is not like a simulated one", and that seems like it argues against more of the same sort of training as a solution to that class of problem.)
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Old 3rd May 2019, 14:06
  #4797 (permalink)  
 
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Originally Posted by Cows getting bigger View Post

737 driver, I have an itch and please take this comment with the best of intent.

When I was taught to fly, PPL through CPL etc, it was instilled in me to understand what every switch/knob did before I played with it (initial thanks to Norman Buddin, ex Hunter pilot and CFI). We were not in the business of altering things without understanding the impact.

So, please correct me if I am wrong, but earlier versions of the 737 had two distinct outcomes associated with the two stab trim switches whilst the Max basically has two switches in series? Somewhere along the line a change operating procedures seem to have pre-dated the wiring change. I’m trying to understand why pre-Max pilots didn’t know, or weren’t told about, the difference between the switches. Isn’t it better airmanship to understand why, what and how when managing aircraft systems, or are we witness to the pre-cursor of ‘Children of the Magenta’ in pilots who never questioned why they threw two switches and what each did?


If it hasn't already become evident, I am also a product of the old school philosophy of pilot training. That being said, there were plenty of times where even I thought we were being required to know far too much technical knowledge than was necessary.

Somewhere along the way, our training started to change. There was far less emphasis on understanding the systems and far more emphasis on following the written procedures. Our training has become highly scripted, and we almost always know the sim training scenarios in advance. I suspect that this change has largely been driven by costs, with modern airlines being reluctant to provide anything other than the minimum training required by the FAA. (You've probably heard the saying, "If the minimum wasn't good enough, it wouldn't be the minimum!")

Frankly, some pilots welcomed this change because it is less work and less threatening. There has always been lip service to the concept that, in some circumstance, the pilot may not have a well-defined checklist or procedure to follow and was expected to use their best judgement. Unfortunately, that sentiment has rarely been backed up with any kind of training. Unfortunately, I think we have seen enough accidents and incidents to in the last decade to show that there is a real, if unaccounted for, cost to this approach to training. Sadly, I still don't see any motivation to make the needed changes to the typical industry training regime. We apparently haven't produced a high enough body count to justify it.

As to your specific question, I have gathered from some of the other posters here that there was no change to their runaway stab trim procedure, that they always used both cutout switches. All I know is that at my airline, we used to be allowed to use them separately. This procedure was changed a few years back (can't remember exactly when, and I don't have any of the old manuals). At the time, I remember being told that this was a Boeing-preferred change driven by a larger trend of removing most types of troubleshooting activities from our non-normal procedures. In my current 737NG manual, there is no longer a reference to the functionality of the two cutout switches. I only know because my experience predates the change. Since current 737NG pilots aren't taught how these switches are wired, I guess there would be little point to telling them how the MAX switches are wired, and as I have previously stated, there is absolutely no difference in the aircraft from a procedural perspective.

Last edited by 737 Driver; 3rd May 2019 at 15:30.
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Old 3rd May 2019, 14:30
  #4798 (permalink)  
 
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35 Seconds is all it took.

Originally Posted by 737 Driver View Post
I will agree that any human pilot at some stage in his training will be easily overwhelmed by even the most basic aircraft emergency scenarios. That is why we train so extensively for them. I had previously posted that in the Ethiopian accident, the Captain did fly the aircraft after a certain fashion, and that he had defaulted to his training. The problem was that he defaulted to the wrong training. Just about all of the ET302 Captain's initial actions can be understood in the context of a normal takeoff profile. Unfortunately, a normal takeoff profile left him in a highly unstable position from which dealing with the ultimate stab trim problem became a bridge too far.
The ET pilot possibly followed the Boeing UAS flow chart I posted earlier that covered AoA failure as a 'false' positive ending with "pilot with correct display becomes pilot flying" which apparently did not happen.

He was able to engage autopilot for 30 seconds (again a questionable move). Until the AP disconnected as flaps were retracted the situation was not extreme, I will leave it to others how 'normal' the profile was.

At 05:40:00 the first MCAS input occurs followed by insufficient re-trim, surprise, lack of training experience with magnitude of MCAS input? This led to rapid speed increase

At 05:40:20 the second MCAS input occurs, interrupted by pilot trim at 04:40:27.
The crew carried out the runaway stab procedure at 05:40:35. From the trace it appears that the pilot may have been trimming at this point and was interrupted by the cutout switches.
Had they waited until AC was in trim we likely would not be discussing this..

Looking at the sequence above: At 05:40:00 the AC was not in extreme state By 05:40:35 they were left with likely inoperable manual trim and approaching, but not yet at VMO.
Things went from "interesting to extreme" in 35 seconds during which the crew followed the runaway trim procedure, albeit without first fully trimming the AC.

From other posts they may not have seen the update procedure with the 'note' about first trimming.

That is 35 seconds with only 2 MCAS inputs to get to an extreme state.

One thing that the prelim report does not cover is what was going on during the two and a half minutes until the final sequence. Surely they were not just sitting there with a couple of ATC exchanges.

Here is one scenario:

Trim cutout, both switches as per procedure

Attempts to use manual trim are not successful due to loading (speed still < VMO)

Pilot remembers 737NG had 2 cutout modes, auto and all, depending on slide ware version he "trained" with the change in MAX may not have been mentioned, even if it was it was not stressed.
They try first one then the other switch, no electric trim.
Further attempts to use manual trim?
Next relevant snip from the report:
At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try.
At 05:41:54, the First-Officer replied that it is not working.
Final puzzle is why only brief trim inputs after they re-enabled trim.









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Old 3rd May 2019, 14:46
  #4799 (permalink)  
 
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Since we have seemingly now moved onto a focus on the human factor element (i.e. the why behind the flight crew errors), I think it might be worthy to expand this topic a bit.

Clearly, these accidents have exposed a case where some presumably highly-trained and experienced professionals were put in a position where that training and experience did not rise to the task. Obvious errors were made that had fatal consequences. Since most of us would like to assume that this wasn't a case of malicious or negligent behavior, then presumably there were some significant human factor element behind these lapses.

I am referring, of course, to the various engineers, technical and supervisory staff that designed and approved MCAS for service.

Imagine, if you will, a parallel online forum in which aircraft-related engineer specialties debate over the various elements of these accidents from their perspective. One could imagine certain individuals saying, "Why didn't they just design the friggin' software/hardware correctly?!" Others might defend their tribe by saying the design was sufficient, it was just that the operators weren't sufficiently skilled/trained to handle a malfunction. Still others might concede that, while yes, errors were made, the individuals who had their hands on the design/approval process were working under various constraints and pressures and that their errors were perfectly understandable from a human factors perspective. They would plead that, please, everyone take a breath and quit trying to blame the engineers when it is obvious they were doing the best they could under the circumstances.

What would we make of such a conversation?

What I am trying to point out is that while some of us like to say "Boeing" messed up or "the FAA" messed up, the reality is that these organizations are simply made up of human beings who respond to their training, experience, and environment. Being human, they are just as much subject to the fallibilities of the human mind as were the pilots. There is even one study that lists precisely 188 types of cognitive errors that the human mind is subject to (click here to read). These errors may be different than the ones the pilots were exposed to, but they were ultimately human errors.

At some point, we will have two final accident reports detailing a list of primary and secondary causes to these accidents. Behind a fair number of these causes will be a human being who was not acting out of malicious intent or neglect. They were simply performing according to their training, experience, and environment. In the discussions on this and related threads, there quite often the refrain, "Stop blaming the pilots!" I don't have any problem with that sentiment since the act of "blaming" is largely an emotional response that tends to avoid getting to the root of the problem. That being said, identifying the root causes and proposing remedies isn't the same as blaming (unless someone chooses to interpret it that way).

So yes, how about we all stop blaming everybody who had a hand in these accidents, understand that behind every error there was likely a human factor element, and support those efforts to address and/or remediate those issues?
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Old 3rd May 2019, 14:55
  #4800 (permalink)  
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Final puzzle is why only brief trim inputs after they re-enabled trim.
I think ( but not sure and wait to be corrected ) what the FDR data published shows is 2 briefs trims movements , .If this is the case , it does not show the actual inputs physically made , it could have been a continuous trim input by the Capt but it only worked twice briefly , possibly because the aerodynamic load on the stab was already very high ? just an attempt to understand it . I do not think the actual trim switches positions are recorded , but as I said, waiting to be corrected .
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