Ethiopian airliner down in Africa
Join Date: Mar 2015
Location: Washington state
Posts: 209
Likes: 0
Received 0 Likes
on
0 Posts
Many pages back, in another thread LEOCh posted a schematic chart showing a nasty inflection between 10 and 15 degrees AOA, which is when MCAS kicks in. Once AOA is below 10 degrees, MCAS unwinds the nose-down trim (unless the pilots intervene with electrical trim inputs
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 62
Posts: 424
Likes: 0
Received 0 Likes
on
0 Posts
This seems like rather complex behavior for the pilots not to be informed about or trained on, especially in a plane that is not advertised as a fly by wire plane. 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?
The assumption must be that the pilot would not "porpoise" the aircraft with the elevator, alternately crossing the MCAS 10 degree AOA threshold. This criterion requires time-smoothing, to avoid random fluctuations of the AOA values (as per the new specification).
Blipping the electric trim (either up or down) during the unwind process, could theoretically put the aircraft in a semi-unstable situation, since MCAS would be disabled, and cannot reactivate again (as per the new specification). Again we must assume that the pilot intentionally wants to keep the nose high for specific reasons (such as high-altitude terrain proximity avoidance). In this scenario MCAS should not try to second guess the flight situation, but rather wait for the pilot to release the elevator yoke (and sort out any trim issues later).
Presumably the MCAS system will be clearly documented to the point where pilots are assured that:
- MCAS will not inhibit the necessary elevator yoke authority during escape maneuvers
- The overall flight system will not produce an out of trim condition when exiting from a maneuver
I seems obvious that Boeing and the FAA will flight test all of this in great detail. Whether an average pilot needs to experience this in a simulator, is an entirely different question (conditions outside the normal flight envelope). The time-delay feedback process is indeed new, and somewhat uncharted territory.
Join Date: Jan 2008
Location: Hotel Sheets, Downtown Plunketville
Age: 76
Posts: 0
Likes: 0
Received 0 Likes
on
0 Posts
-
Yes, I’ve seen the video, and yes I agree that it appears the Captain had achieved cognitive overload. Where I differ is that I feel the circumstances were not so extreme that cognitive overload would have been a reasonable expectation of a 737 type-rated Captain.
I used to do basic flight instruction, and I’ve seen many types of students. I would often tell them that flying an aircraft on a nice day really wasn’t that difficult once you had a little time under your belt, not too unlike learning to drive an automobile. The huge difference between a car and a plane, of course, is that you just can’t pull an aircraft over on the shoulder when things go wrong. 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.
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, I’ve seen the video, and yes I agree that it appears the Captain had achieved cognitive overload. Where I differ is that I feel the circumstances were not so extreme that cognitive overload would have been a reasonable expectation of a 737 type-rated Captain.
I used to do basic flight instruction, and I’ve seen many types of students. I would often tell them that flying an aircraft on a nice day really wasn’t that difficult once you had a little time under your belt, not too unlike learning to drive an automobile. The huge difference between a car and a plane, of course, is that you just can’t pull an aircraft over on the shoulder when things go wrong. 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.
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.
Join Date: Sep 2006
Location: Pergatory
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
I couldn`t disagree more. To fly the modern airliners you fly the automatics. If for whatever reason you cannot do that then its very much up to the avionics to do whatever they have been setup to do. These guys did not have a cats in hell chance of persuading the automatics to allow them to interfere. They simply lost the very short argument with the machine. What sort of last line of defense is that, is it a bit like the Maginot Line, invincible until proven otherwise and how many times does it need to be demonstrated before someone realises it aint working. Give me human error any day, I can understand that, computers, electronics and all that wizardry that goes with them, let the kids addicted to them play with it all, that would be a whole load safer.
Join Date: Nov 2012
Location: New York
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
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.
I couldn`t disagree more. To fly the modern airliners you fly the automatics. If for whatever reason you cannot do that then its very much up to the avionics to do whatever they have been setup to do. These guys did not have a cats in hell chance of persuading the automatics to allow them to interfere. They simply lost the very short argument with the machine. What sort of last line of defense is that, is it a bit like the Maginot Line, invincible until proven otherwise and how many times does it need to be demonstrated before someone realises it aint working. Give me human error any day, I can understand that, computers, electronics and all that wizardry that goes with them, let the kids addicted to them play with it all, that would be a whole load safer.
Join Date: Jan 2008
Location: Hotel Sheets, Downtown Plunketville
Age: 76
Posts: 0
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Apr 2019
Location: East Coast
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
- 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.
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.
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.
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.
Psychophysiological entity
Quote:
Originally Posted by GordonR_Cape 
.
Many pages back, in another thread LEOCh posted a schematic chart showing a nasty inflection between 10 and 15 degrees AOA, which is when MCAS kicks in. Once AOA is below 10 degrees, MCAS unwinds the nose-down trim (unless the pilots intervene with electrical trim inputs
Water pilot: #4242 My bold.
This seems like rather complex behavior for the pilots not to be informed about or trained on, especially in a plane that is not advertised as a fly by wire plane.
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?
GordonR carries the logic forward in the next thread.
Join Date: Apr 2019
Location: USA
Posts: 217
Likes: 0
Received 0 Likes
on
0 Posts
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; 23rd Apr 2019 at 23:22. Reason: Clarity
Join Date: Nov 2011
Location: Chicago
Age: 66
Posts: 35
Likes: 0
Received 0 Likes
on
0 Posts
Quote:
Originally Posted by GordonR_Cape
.
.
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.
Join Date: Apr 2019
Location: USA
Posts: 217
Likes: 0
Received 0 Likes
on
0 Posts
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.
Psychophysiological entity
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?
Join Date: Mar 2009
Location: HK
Posts: 95
Likes: 0
Received 0 Likes
on
0 Posts
It is manufactures, authorities and airlines obligation to cater for this reality. Once again, unfortunately.
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.
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?
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 62
Posts: 424
Likes: 0
Received 0 Likes
on
0 Posts
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.
Join Date: Apr 2008
Location: Paris
Age: 74
Posts: 275
Likes: 0
Received 0 Likes
on
0 Posts
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