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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 25th Apr 2019, 17:16
  #4321 (permalink)  
 
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Originally Posted by 737 Driver View Post
Yes, it really was that easy.
Do you know what their long term shift pattern was? Have you read the FlyDubai Rostov crash thread? Do you know why they didn't quite get it back in trim? Why they just blipped the switches during the second MCAS activation? They did pretty much everything you ask for, just not quite enough of it. Why? They even identified the issue and operated the cutouts.

Perhaps misleading alarms, violence of stick shaker masking clack of trim, possibility of a number of causes to go through, speed of MCAS operation, repetition of MCAS, startle factor, no sim training for specific event? Fatigue? Heck even Sully said he had a lot of luck, and it took him quite a few seconds for real cognition to come in. And he had none of the above to contend with, just a nice quiet cockpit.

They were acting as test pilots for a failure mode that was easily predictable, that never should have been allowed to pass design stage never mind FMEA and testing. Boeing's responsibility.

You've made up your mind but I'd prefer to give a little slack to two dead guys who had to add "systems faulting engineer" to their CV at the drop of a hat.
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Old 25th Apr 2019, 17:25
  #4322 (permalink)  
 
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Slight reframing of the issue starting with some assumed true statements, mostly applies to both accidents although the lion air prelim report does not show control column positions.

1: The pilots were initially aware that the plane was out of trim through no action on their part.

2: They counteracted some but not all of the MCAS inputs.

3: The last moments of both flights saw brief manual trim inputs, woefully insufficient.

The question is why did both crews only partially retrim and then loose it at the end?
Possible answers, not mutually exclusive of course.

A: They were confused by all the warnings and just lost the plot.

B: They had no training with grossly out of trim conditions and were used to short inputs.

C: Something confused them after the initial re-trim to believe the airplane was close being in trim, despite the obvious control column in lap.
Could they have believed that some other factor was causing this?

D: Some biomechanical or other issue prevented them from actuating the switches.

As others have stated 'basic airmanship' should have worked but clearly something was missing.
Note, There were also a large number of other factor that could have prevented these accidents, especially ET, this is just about why the crew did what they did.
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Old 25th Apr 2019, 17:26
  #4323 (permalink)  
 
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Originally Posted by GordonR_Cape View Post
I certainly did look at the ET 302 FDR readout, before posting my comment. The question is why did the pilot stop nose up trim inputs at 2.5 degrees? There were still considerable control column forces shown on the FDR. Why would any pilot only half trim out those forces, unless they were stopped by software or hardware? My question remains unanswered...
I had the exact same question when I first read the accident report. I spent a lot of time looking for evidence that the trim motor stalled or the trim switch wasn't working. However, none of the accident evidence or any historical data supports either of these conclusions.

One of the most telling pieces of evidence in this report, however, is that the Captain repeatedly tried to engage the automation (three times) in a situation that specifically precluded it. This is evidence of someone with a strong case of automation dependency. People with significant automation dependency also demonstrate a deterioration in basic hand-flying skills. Combine that with the startle effect and the distraction of the active stick shaker, it is entirely conceivable that the Captain suffered from cognitive overload and simply forgot to trim because it had never become a thoroughly engrained behavior.
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Old 25th Apr 2019, 17:40
  #4324 (permalink)  
 
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I can understand a reluctance to fight the aircraft to dramatically alter the trim when the issue is not clear.

Many road vehicle crashes are made worse by tentative breaking when only full force could have helped. (Several car makers initially added brake force acceleration systems to increase partial braking towards full pressure for this reason - now augmented by radar anti-collision systems)
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Old 25th Apr 2019, 17:44
  #4325 (permalink)  
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Originally Posted by 737 Driver View Post
The STS would not have been active with flaps up.
So, do you still consider MCAS an STS subsystem ?
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Old 25th Apr 2019, 17:48
  #4326 (permalink)  
 
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Those two short electric trim-up commands at the end of both crashes just before enter info a dive keep puzzling me... Farfetched maybe, and probably repeating what others have suggested already, but what about:

E: The electric trim didn't move the trim wheel at all. Flip up once, no trim wheel movement. Try it another time, still no movement. The pilots conclude electric trim it isn't working and proceed (and the MCAS steps in again).

SLF
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Old 25th Apr 2019, 17:49
  #4327 (permalink)  

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Can I just highlight that the F/O had 200hrs experience. I didn't get a commercial pilots licence until I had flown 230 hours and didn't fly jets until I had 1800hrs. The company that I flew 737's for in the UK in the early 1970's required 2000 hours before offering a job in the right hand seat.

This incident was to all intents and purposes a single pilot operation.
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Old 25th Apr 2019, 17:49
  #4328 (permalink)  
 
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Originally Posted by Lost in Saigon View Post
Yes, I agree. It SHOULD have been easy, but for some unknown reason, it was not.

There are at least three things that could have saved them:

1) leaving the flaps extended to stop MCAS operation
2) using electric trim to stop MCAS operation
3) using the stab trim cutout switches to stop MCAS operation

They did NONE of these things CORRECTLY. We need to find out why.

Hopefully the final report will give us the answer.
So above-average pilots would have saved the plane and below average pilots lose it. Let's see, there are 50% of below average pilots in the world, you better be careful when an SLF to get in the right plane - although of course only above average pilots participate in PPRuNe.

Gimme a break - the issue is why were the pilots subjected to this horrible situation, where being average but not good meant bye bye for the SLF?

Edmund
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Old 25th Apr 2019, 17:58
  #4329 (permalink)  
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Posted in error on the parallel thread.

737Driver
post number #4304
Quote:
First of all, some of you might be surprised to learn that in a stall condition, the STS will trim the stab nose down at the exact same speed as MCAS and can do so continuously until it hits the stop. This is far more authority than MCAS ever had. Why is not a problem? Because the STS will respect the control column trim cutout switches. These are not the pedestal switches that are activated by the pilot. These limit switches are located at the base of the control column and prevent trimming opposite the direction of column displacement. That is, if a pilot is pulling back on the yoke, then nose down trim is inhibited. If someone is pushing forward on the yoke, nose up trim is inhibited. Thus the authority of STS is limited by the control inputs of the pilot.
One of the bees in my bonnet has been the removal of that column switch on the MAX. Not just the bypassing of its logic under certain conditions - but the total physical removal.

Despite being in my 80th year, (and posting on the wrong thread) statements like that still stick firm, like the unwinding of MCAS. The switch removal (from under the floor at base of column) never really got a clear answer. Well it did: a dedicated post saying 'I don't know'.

I try to filter my information input, and of course a lot is from the Times publication and our engineering friend in Seattle. The switch is either there, or not there, but it seems if it is, its functionality can be obviated as per 737 Driver's earlier post.

Back to his assertion that it was flyable. I get a sickening feeling that something else apart from psychological overload might be wrong. There are so many able minds chasing the suspected faulty input to that 47' of flying surface, along with the associated loading difficulties, that you'd think remedial action was just a matter of time. But the thing I fear most is months of rewriting of code, some agreement on what is now certification and the craft back in the sky carrying a ghost in the machine.

There is too much pressure to get airborne.

'We' seem to have everything we need to throw light on those terrible moments, but the very fact that so many skilled people, not least of all on this forum, can disagree on the extent of the pilot culpability worries me deeply. There is a huge dichotomy in the judgement of these flying professionals.
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Old 25th Apr 2019, 17:58
  #4330 (permalink)  
 
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Originally Posted by nyt View Post
So, do you still consider MCAS an STS subsystem ?
That was actually Boeing's position, not mine. That being said, there are regime's in which the traditional STS is inhibited, and regimes in which the MCAS is inhibited. These regime's are mutually exclusive.
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Old 25th Apr 2019, 18:06
  #4331 (permalink)  
 
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Originally Posted by edmundronald View Post
So above-average pilots would have saved the plane and below average pilots lose it.
Someone may have said this, but that is certainly not my position.

Let me restate it. There are certain expectations of a professional pilot who is entrusted with the lives of their passengers and crew. One of those expectations is that, in the presence of an unexpected aircraft state, they should be able to demonstrate the basic airmanship skills of hand-flying their aircraft by establishing the appropriate attitude and power settings, monitoring aircraft performance (speed, altitude, rate of climb, etc), and keeping the aircraft in proper trim.

This is an expectation for ALL professional pilots. Not above average. Not average. ALL.
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Old 25th Apr 2019, 18:06
  #4332 (permalink)  
 
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I certainly agree with your comments about the hand flying skills.
On an 8 hour atlantic sector how much time does a pilot actually fly the aircraft ?, 5 mins, bit more bit less ?.
How out of practice do you get after 5 or 10 years of just systems management ?.
I know some commercial pilots fly light aircraft for fun, but how many dont ?.
I think all commercial pilots should have to fly a manual light aircraft and fly some aerobatics at least 5 hours a year.
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Old 25th Apr 2019, 18:10
  #4333 (permalink)  
 
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Clueless posts drowning out the valuable ones

737 driver is obviously a professional pilot flying the 737. As a 737 NG Captain myself I can assure you he knows what he is talking about. He is an expert on the subject and the majority of the posters arguing with him are not. It is amazing and at the same time quite frustrating to observe the conviction with which people are stating their opinions on here even though they are actually clueless.
Instead of posting your ignorant armchair pilot comments, why don't you take some time to read up on the procedures to fly the 737. Read the official Boeing documents. Talk to 737 pilots and ask them how they are trained. Of course this will take a lot longer and require much greater effort than posting your oblivious comments but then you might be a little bit closer to actually being able to judge how these pilots performed.
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Old 25th Apr 2019, 18:22
  #4334 (permalink)  
 
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Originally Posted by GordonR_Cape View Post
- MCAS was designed to activate at a much lower AOA, independent of the stick shaker.
- MCAS was designed to activate under many areas of the flight envelope, independent of the stick forces and airspeed.
2 things -

1) Do you have a reference for what AOA MCAS activates at when compared to the stickshaker AOA, preferably from a primary source, i.e. the manufacturer, a regulatory body, or similar? I've looked for that but have been unable to find it... it's getting difficult to find original data among all the poorly written media interpretations.

2) I do not believe that is true. Airspeed is used both as in input to determine the MCAS activation AOA, and it is used to determine the magnitude of the stab trim input. The first time that we learned anything about MCAS was in the November 8/9/10 timeframe in a letter from Mike Michaelis, APA safety committee chairman. It was an unpublished letter to APA members but was extensively reported in the media, and claimed to include a description of MCAS that was provided by Boeing. Here's a contemporary PPRuNe link - Indonesian aircraft missing off Jakarta

The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.



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Old 25th Apr 2019, 18:23
  #4335 (permalink)  
 
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Hmmmm, is he the same as the 4 professional pilots who were flying the two planes that crashed ?.
Maybe all of those 4 were below average, and he is above average ?.

Being professional in any job doesnt make you automatically good at it at all. it just means you get paid for it.
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Old 25th Apr 2019, 18:30
  #4336 (permalink)  
 
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Originally Posted by 737 Driver View Post
That was actually Boeing's position, not mine.
That's also the FAA's position, at least based on the most recent FSB report draft. https://www.faa.gov/aircraft/draft_d...ev17_draft.pdf

B-737-MAX Maneuvering Characteristics Augmentation System (MCAS). The Speed Trim System (STS) provides speed and pitch augmentation. Speed stability augmentation is provided by the Speed Trim function of STS. Pitch stability augmentation is provided by the MCAS function of STS. MCAS ground training mustaddress system description, functionality, associated failure conditions, and flight crew alerting. These items must be included in initial, upgrade, transition, differences, and recurrent training.





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Old 25th Apr 2019, 18:43
  #4337 (permalink)  
 
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Originally Posted by edmundronald View Post
So above-average pilots would have saved the plane and below average pilots lose it. Let's see, there are 50% of below average pilots in the world, you better be careful when an SLF to get in the right plane - although of course only above average pilots participate in PPRuNe.

Gimme a break - the issue is why were the pilots subjected to this horrible situation, where being average but not good meant bye bye for the SLF?

Edmund
Average professional pilots even below average professional pilots should note and correct out of trim flight. This is C-172 stuff and is not complicated. The first Lion Air flight showed that the Max with MCAS erroneously operating is flyable by repeated trimming, the second flight showed that had the captain continued trimming back to in trim the flight may not have crashed; it was only when the trimming was reduced to the occasional blip that control was lost. If trimming had continued and a return to airport was chosen as soon as the flaps were lowered MCAS would have stopped and the aircraft could have recovered.

Boeing had an expectation that qualified 737 pilots would continually keep the aircraft in trim and that would stop MCAS, They also had the expectation that repeated uncommanded nose down stab trim by the aircraft systems would result in the stab trim being switched off by a qualified 737 pilot. Boeing was wrong. 737 pilots qualified and allocated their seats by their airline did not do as Boeing expected. It seems that automation surprise plus all the alerts aural and haptic (the stick shaker) amplify the automation surprise to a level where some pilots can no longer 'fly the plane'. It may be that the simulation training may not provide the visceral reality of an emergency in the real aircraft resulting in cognitive tunneling or even an attempt to carry on as if the system failure hadn't happened. I and no doubt others here, have witnessed examples where competency shown in the simulator falls apart in the 'real world',

So while Boeing is building aircraft that would be easily flyable by 737 pilots from the 1970's who usually flew manually and often preferred to switch off the automation; the training systems and the airline training constraints are producing pilots who avoid and are instructed to avoid, manual flying and who are better at system management. This has become apparent in this thread where there is a rough distinction between the 'switch it off' - pitch and power - fly the aircraft group (smaller); and, the systems managers who need to know all the aspects of the system with an FMEA and NNCs geared to each of those failure modes. The first group are aghast the aircraft were not recovered, the second are aghast that a new part of the system was not flagged up by Boeing and was not briefed with precise NNCs.

Aviation seems to have met the cross over point where avionics manufacturers and airframers can no longer assume that any bag of bolts on failure will be picked up by someone 'aviating', 'navigating' and 'communicating' - setting pitch, power, trimming and flying the aircraft; they now have to remove all potential single-points-of-failure, fail soft, gracefully degrade, and, if possible automation should carry on and cope with all potential failure modes. However, that is a slippery slope as it is a self fulfilling prophecy the more capable the automation the less capable the pilots. The only ones happy about that are the beancounters who will further reduce simulation time accelerating the problem.

Last edited by Ian W; 25th Apr 2019 at 18:45. Reason: grammar
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Old 25th Apr 2019, 18:51
  #4338 (permalink)  
 
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Originally Posted by 737mgm View Post
737 driver is obviously a professional pilot flying the 737. As a 737 NG Captain myself I can assure you he knows what he is talking about. He is an expert on the subject and the majority of the posters arguing with him are not. It is amazing and at the same time quite frustrating to observe the conviction with which people are stating their opinions on here even though they are actually clueless.
Instead of posting your ignorant armchair pilot comments, why don't you take some time to read up on the procedures to fly the 737. Read the official Boeing documents. Talk to 737 pilots and ask them how they are trained. Of course this will take a lot longer and require much greater effort than posting your oblivious comments but then you might be a little bit closer to actually being able to judge how these pilots performed.
I'm not a pilot, but also not clueless (having both an engineering and programming background), and having read all 4000 plus posts in this thread. My questions have not been about how to fly a B737, but how the MAX and MCAS actually work, with stuck high AOA data. No pilot on this forum has actually experienced this, either in person or in the simulator. I (and others) do not accept as verbatim truth, the system descriptions provided by such pilots, however experienced. The same applies even more to Boeing, who were evasive about the existence of MCAS, provided limited documentation, and have much to gain by shifting blame, and good (legal) reasons for not disclosing more details.

Only an independent engineering verification (not paper documents and diagrams) of the details of systems involved in the crashes, and of the proposed revisions to MCAS, will provide all the answers. My viewpoint has nothing to do with blame, just looking for the truth, which may take some time (years?). In the meantime any assertion that the pilots should have done X, can be countered by an assertion that perhaps the software or hardware did not allow that to happen. The same is true of any crash investigation, where both complex systems and human factors were involved.
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Old 25th Apr 2019, 19:05
  #4339 (permalink)  
 
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Originally Posted by GordonR_Cape View Post
I'm not a pilot, but also not clueless (having both an engineering and programming background), and having read all 4000 plus posts in this thread. My questions have not been about how to fly a B737, but how the MAX and MCAS actually work, with stuck high AOA data. No pilot on this forum has actually experienced this, either in person or in the simulator. I (and others) do not accept as verbatim truth, the system descriptions provided by such pilots, however experienced. The same applies even more to Boeing, who were evasive about the existence of MCAS, provided limited documentation, and have much to gain by shifting blame, and good (legal) reasons for not disclosing more details.

Only an independent engineering verification (not paper documents and diagrams) of the details of systems involved in the crashes, and of the proposed revisions to MCAS, will provide all the answers. My viewpoint has nothing to do with blame, just looking for the truth, which may take some time (years?). In the meantime any assertion that the pilots should have done X, can be countered by an assertion that perhaps the software or hardware did not allow that to happen. The same is true of any crash investigation, where both complex systems and human factors were involved.
There are two issues at hand here: One issue is everything surrounding MCAS which you are interested in. Another issue is, if these accidents were preventable by carrying out the required Boeing procedures or by applying basic flying skills respectively, despite MCAS activating.
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Old 25th Apr 2019, 19:09
  #4340 (permalink)  
 
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Originally Posted by Loose rivets View Post
Posted in error on the parallel thread.

737Driver
post number #4304
Quote:
One of the bees in my bonnet has been the removal of that column switch on the MAX. Not just the bypassing of its logic under certain conditions - but the total physical removal.

Despite being in my 80th year, (and posting on the wrong thread) statements like that still stick firm, like the unwinding of MCAS. The switch removal (from under the floor at base of column) never really got a clear answer. Well it did: a dedicated post saying 'I don't know'.

I try to filter my information input, and of course a lot is from the Times publication and our engineering friend in Seattle. The switch is either there, or not there, but it seems if it is, its functionality can be obviated as per 737 Driver's earlier post.

Back to his assertion that it was flyable. I get a sickening feeling that something else apart from psychological overload might be wrong. There are so many able minds chasing the suspected faulty input to that 47' of flying surface, along with the associated loading difficulties, that you'd think remedial action was just a matter of time. But the thing I fear most is months of rewriting of code, some agreement on what is now certification and the craft back in the sky carrying a ghost in the machine.

There is too much pressure to get airborne.

'We' seem to have everything we need to throw light on those terrible moments, but the very fact that so many skilled people, not least of all on this forum, can disagree on the extent of the pilot culpability worries me deeply. There is a huge dichotomy in the judgement of these flying professionals.
It is the last paragraph of the above post that also concerns me. I am dismayed to read on this forum that there are those who suspect culpability on the part of the pilots. Here is an extract from Dominic Gates article in the Seattle Times

"Flawed analysis, failed oversight: How Boeing, FAA certified the suspect 737 MAX flight control system"As Boeing hustled in 2015 to catch up to Airbus and certify its new 737 MAX, Federal Aviation Administration (FAA) managers pushed the agency’s safety engineers to delegate safety assessments to Boeing itself, and to speedily approve the resulting analysis."

The full article may be accessed at : https://www.seattletimes.com/busines...ion-air-crash/

"But the original safety analysis that Boeing delivered to the FAA for a new flight control system on the MAX — a report used to certify the plane as safe to fly — had several crucial flaws."

How could it be that when so much has been published about this accident, some can still consider culpability may still be suspected on the part of the pilots. Is this not yet another case of a race between competitors, just as it was back in the late 60`s, early 70`s for the first wide body jets and the Turkish DC10 crash.
Always easy to blame the pilots, perhaps this is why in today`s age of high tech, computers, robotics, automation, that pilots are still "carried" on board the modern airliner.


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