Ethiopian airliner down in Africa
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Originally Posted by LowObservable
I am amazed at the continued "any real airman could have handled this... obvious trim runaway... follow the procedures" drumbeat from people who identify as US- or Euro-based pilots. (I say "identify" because at least one such got outed as a sim player.)
People! So far we know of only three occurrences of the basic failure (AoA sensor is bad from the start of roll, falsely high reading, high enough for stall warning, and it's the one driving MCAS today). Two resulted in total loss. The third was saved by a jumpseat rider who had attention to spare and a better view of the trim wheels. That is stark evidence that this failure sequence is dangerous in the extreme.
Moreover, airlines all over the world have, in recent years, contributed to the industry's excellent safety record. Not too many signs that (not to put too fine a point on it) the ethnicity of the pilots or management is a big deal.
People! So far we know of only three occurrences of the basic failure (AoA sensor is bad from the start of roll, falsely high reading, high enough for stall warning, and it's the one driving MCAS today). Two resulted in total loss. The third was saved by a jumpseat rider who had attention to spare and a better view of the trim wheels. That is stark evidence that this failure sequence is dangerous in the extreme.
Moreover, airlines all over the world have, in recent years, contributed to the industry's excellent safety record. Not too many signs that (not to put too fine a point on it) the ethnicity of the pilots or management is a big deal.
As a side note, I have invested a fair amount of personal time researching issues related to these accidents to include sifting through available aviation safety and accident databases. There have been plenty of other cases of commercial airline instrument failures leading to unexpected system responses and confusion among the crew. You just don’t hear about them because these events had a successful conclusion.
The notable exception was AF447 - loss of airspeed, confusing alerts, systems reacting in ways the pilot flying wasn’t expecting, improper crew response, followed by a hull loss and major loss of life. This was another clear example of the pilots’ failure to revert to basics and fly the aircraft. Their ethnicity or employment at a major European carrier granted them no special protection from a failure of airmanship.
Last edited by 737 Driver; 24th Apr 2019 at 00:22. Reason: Clarity
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Originally Posted by Loose rivets
Quote:
Originally Posted by GordonR_Cape
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Water pilot continues below, but a point I've been wondering about for ages. MCAS winds back after it's done its thing? So little has been made of this - apart from me - that I wondered if I'd misunderstood. However, it seems that if the PF uses the electric trim, this will not happen. Since there was extensive use of the thumb switch trim, I guess this is why MCAS at no stage put things back where it found them. Erm, did it?
What a vital observation.
GordonR carries the logic forward in the next thread.
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Originally Posted by Water pilot
When exactly does MCAS start to unwind the trim and in the worst case scenario how much uncommanded nose down trim does the pilot have to unwind if they happen to have blipped the trim switch at the wrong point in the unwind scenario?
Psychophysiological entity
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Well at some stage waaaaaaaay back I read the unequivocal statement that it does. As mentioned, I couldn't understand why I wasn't hearing more about that.
Now, Squinty makes this vital point as well as the thumb switch factor.
The issue is, does it if fact do it, (when all but a high AoA is normal)
Now, Squinty makes this vital point as well as the thumb switch factor.
Doesn't there need to be a *working* AOA sensor that actually provides decreased AOA with the application of stabilizer by MCAS before MCAS will unwind? Why would unwind if it still thinks the AOA is too high?
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Originally Posted by 737 Driver
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You have to take whatever comes, work with whatever you have, and do your damnedest to get the aircraft safely back on the ground. I would tell my students that if they could not deal with that reality, then they should not become a pilot.
You have to take whatever comes, work with whatever you have, and do your damnedest to get the aircraft safely back on the ground. I would tell my students that if they could not deal with that reality, then they should not become a pilot.
It is manufactures, authorities and airlines obligation to cater for this reality. Once again, unfortunately.
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As professional pilots, we ought to meet an even much higher standard. When things started to go wrong, at least one of these pilots needed to look past the noise, place their hands firmly on the yoke and throttles, set the proper attitude and power settings, keep the aircraft in trim, and stay away from the rocks. That was all that was required. Everything else could have waited. The plane wasn’t on fire, the wing didn’t fall off, there were no bombs on board. This plane was flyable.
Yes, Boeing fracked up. Yes, the FAA and the airlines were culpable of going along with the fiction that the MAX wasn’t really that much different from the NG. But you know what? On any given day someone else could screw up and give us an aircraft that will malfunction in a unique and potentially dangerous way. And as always, the pilots are the last line of defense. We need to be mentally prepared for that reality or find another line of work.
Yes, Boeing fracked up. Yes, the FAA and the airlines were culpable of going along with the fiction that the MAX wasn’t really that much different from the NG. But you know what? On any given day someone else could screw up and give us an aircraft that will malfunction in a unique and potentially dangerous way. And as always, the pilots are the last line of defense. We need to be mentally prepared for that reality or find another line of work.
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Only thing Icarus it was not the crew that saved that flight (from the reports).
There seems very little info on this previous Lion Air flight and I/we do not know when the incorrect MCAS input was given. We do know on the two crash flights it was soon after take off, and either after flaps 0 selected or the flaps had fully retracted.
From memory a number of pilots have done the Lion Air & Ethiopian events in the MAX simulator (knowing they will have a MCAS simulation) and they did manage to land safely but said it was "very challenging" - so in a surprise event, the numbers of successful outcomes will reduce. I would have very little doubt the pilots used to do these simulator events, post crashes were nothing but extremely capable pilots selected by Boeing. So in reality it should not have been a challenge at all as many have mentioned, but a breeze or a non event - or did Boeing use substandard pilots for this simulation?
There seems very little info on this previous Lion Air flight and I/we do not know when the incorrect MCAS input was given. We do know on the two crash flights it was soon after take off, and either after flaps 0 selected or the flaps had fully retracted.
From memory a number of pilots have done the Lion Air & Ethiopian events in the MAX simulator (knowing they will have a MCAS simulation) and they did manage to land safely but said it was "very challenging" - so in a surprise event, the numbers of successful outcomes will reduce. I would have very little doubt the pilots used to do these simulator events, post crashes were nothing but extremely capable pilots selected by Boeing. So in reality it should not have been a challenge at all as many have mentioned, but a breeze or a non event - or did Boeing use substandard pilots for this simulation?
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Originally Posted by 737 Driver
MCAS does not “unwind” any of the nose down trim it has inputted. The expectation is that the pilots will put in the correct trim as they recover from the impending stall. We do stall recovery training regularly in the sim, and there is always a lot of retrimming involved.
Any automated (and previously undocumented) system that left an aircraft out of trim after a "simple" maneuver, could never possibly be certified. Stall escape implementated by the pilots is an entirely different matter, as was the runaway behaviour of MCAS due to a stuck AOA sensor.
This discussion is around a not previously considered human/machine feedback process, driven by a delayed trim unwinding process, and subject to interruption by pilot trim inputs. This point seems not to have been covered in any other forum, other than the brief hint, and useful chart, referenced earlier in this thread.
This may turn out to be a non-issue, if properly implemented and documented. It is definitely the kind of concern to be discussed by the Joint Authorities Technical Review.
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Originally Posted by 737 Driver
Okay, as one of the posters who has been highly critical of the airmanship displayed by the accident pilots, would you please show me where I said anything denigrating about their ethnicity or nationality? Poor airmanship is poor airmanship regardless of race, creed, gender, citizenship, favorite football squad, or whatnot. And if it makes you feel any better, I believe the problem lies more in the training and airline culture in which they were raised than any individual shortcomings.
As a side note, I have invested a fair amount of personal time researching issues related to these accidents to include sifting through available aviation safety and accident databases. There have been plenty of other cases of commercial airline instrument failures leading to unexpected system responses and confusion among the crew. You just don’t hear about them because these events had a successful conclusion.
The notable exception was AF447 - loss of airspeed, confusing alerts, systems reacting in ways the pilot flying wasn’t expecting, improper crew response, followed by a hull loss and major loss of life. This was another clear example of the pilots’ failure to revert to basics and fly the aircraft. Their ethnicity or employment at a major European carrier granted them no special protection from a failure of airmanship.
In the case of the Max, the issue of "foreign carriers, foreign pilots" is getting raised as a way for Boeing and the FAA critters to wrangle their way out of a proper accounting for a design and certification process failure, with the dog whistle that the "foreigners" shouldn't be allowed to cash in on the liability payments generously provided by US courts to US victims.
Everyone here is very aware that if 400 US citizens had died in 2 plane crashes, Boeing would be facing serious financial consequences, and there would be a real congressional inquiry re. the FAA's somewhat lax certification practices.
Nobody anywhere in the world believes that the pilots on board the two sadly doomed airframes were anything other than perfectly average trained individuals. In fact Boeing's customers mostly employ pilots of average abilities, because they employ a lot of pilots. There may be some retired fastjet pilots in the trade, but they are now outnumbered by civilians.
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
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Originally Posted by GordonR_Cape
MCAS absolutely should unwind the nose down trim once the AOA drops below 10 degrees (as long as no pilot trim input occurs). I don't have the detailed reference, but this was the whole point of MCAS.
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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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Originally Posted by DaveReidUK
I'd be very interested to see a reference that says that.
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.
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 08:58.
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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
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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Originally Posted by DaveReidUK
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:
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:
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Originally Posted by GordonR_Cape
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 best simple description is a single sentence from b737.org.uk: 737 MAX - MCAS
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Originally Posted by 737 Driver
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.
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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Originally Posted by 737 Driver
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.
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 18:10. Reason: Fixed broken link
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Originally Posted by DaveReidUK
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
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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Originally Posted by edmundronald
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
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)?
