Breaking news: Ethiopian Airlines flight has crashed on way to Nairobi

[Evan]

You do need at least a little bit of extra authority to pitch up from one to the other, but Ethiopian had that extra authority all the way to the last activation of the MCAS (see proof below), and after that point reducing the throttle would not have helped the tiniest bit in any way anyway, the only solution by then was to trim up with the thumb switch (duh!).

And again, I am talking about not getting to that point. From 05:40:00 to 05:40:45 (45 seconds!) they gain about 100kts or airspeed, 100 fatal knots that cause stabilizer forces to become detrimental to manual trim recovery. During this time, there are significant nose-up column inputs. During this time the aircraft is flying more or less level (even slightly descending). During this time the thrust remains at around 98% N1. Level flight + take-off thrust = acceleration.

Now, the discussion is about getting out of a situation in which it becomes difficult to manually trim the 737 in pitch, due to overwhelming aerodynamic forces which are the result of excessive airspeed. That excessive airspeed was caused by thrust without pitch for an extended period of time. Had they reduced thrust somewhere soon after 05:40:00, the speed would not have increased an additional 150kts at the point that MCAS reactivated. Then it should have still been possible to counter-trim manually, there would have been no need to reactivate the electric trim and no reactivation of MCAS would have ever occurred.

If they had been flying at or near 250kts, they would have had full trim authority with the electric trim (and thus MCAS) safely deactivation for the duration of the flight.

[Gabriel]

And again, I am talking about not getting to that point. From 05:40:00 to 05:40:45 (45 seconds!) they gain about 100kts or airspeed, 100 fatal knots that cause stabilizer forces to become detrimental to manual trim recovery. During this time, there are significant nose-up column inputs. During this time the aircraft is flying more or less level (even slightly descending). During this time the thrust remains at around 98% N1. Level flight + take-off thrust = acceleration.

Now, the discussion is about getting out of a situation in which it becomes difficult to manually trim the 737 in pitch, due to overwhelming aerodynamic forces which are the result of excessive airspeed. That excessive airspeed was caused by thrust without pitch for an extended period of time. Had they reduced thrust somewhere soon after 05:40:00, the speed would not have increased an additional 150kts at the point that MCAS reactivated. Then it should have still been possible to counter-trim manually, there would have been no need to reactivate the electric trim and no reactivation of MCAS would have ever occurred.

If they had been flying at or near 250kts, they would have had full trim authority with the electric trim (and thus MCAS) safely deactivation for the duration of the flight.

"All the way up to the last activation of the MCAS" includes between 5:40:00 and 5:40:45 (which is between the point of first MCAS activation to the point where they disconnected the electric trim with the cutout switches).
At ANY point where they could have throttled back, they also could have pulled back to pitch up, keeping speed in check even with full thrust, while climbing and avoiding the nose-down pitch moment associated with thrust reduction.

[Evan]

"All the way up to the last activation of the MCAS" includes between 5:40:00 and 5:40:45 (which is between the point of first MCAS activation to the point where they disconnected the electric trim with the cutout switches).
At ANY point where they could have throttled back, they also could have pulled back to pitch up, keeping speed in check even with full thrust, while climbing and avoiding the nose-down pitch moment associated with thrust reduction.

You might want to take another look at the FDR between 5:40:00 And 5:40:45. Especially the part labeled "Aft Column Inputs".

[Gabriel]

You might want to take another look at the FDR between 5:40:00 And 5:40:45. Especially the part labeled "Aft Column Inputs".

I did, it doesn't change from the figure I attached in the previous post. All the way from the 1st MAS activation to the final MCAS activation the control column position oscillated around about 8 degrees. After the final MCAS activation they pulled to 14 degrees. As as I said, at ANY point (and with ANY I mean ANY) before the last MCAS activation, they had elevator authority (and arm strength) to pull up. That includes ANY point where you may suggest they should have reduced the throttles.

[Evan]

I did, it doesn't change from the figure I attached in the previous post. All the way from the 1st MAS activation to the final MCAS activation the control column position oscillated around about 8 degrees. After the final MCAS activation they pulled to 14 degrees. As as I said, at ANY point (and with ANY I mean ANY) before the last MCAS activation, they had elevator authority (and arm strength) to pull up. That includes ANY point where you may suggest they should have reduced the throttles.

Now you're really confusing me. From 05:40:40 to 05:40:45. the column inputs exceed 10° back, while the actual pitch displacement never exceeds 5° ANU. Power remains at take-off setting. Thus the aircraft gains 100kts and exceeds Vmo.

But then we have Mentour Pilot showing us how, in mistrim at Vmo+, he needs all his strength to keep the nose up and his FO can't move the stab trim wheel.

Ethiopian was at Vmo+ from 05:40:45 until beyond 05:43:15 when the electric trim is restored (presumably because the FO couldn't move the trim wheel).

It was at that speed because thrust remained at take-off setting, stab trim was stuck at 3 units (ANU) and pitch never managed to get above 8° and was occasionally negative (presumably due to extreme mistrim forces).

So, speed on elevator isn't working, we need to slow down to get manual control authority back, what else have we got? Oh right, power levers!

[flashcrash]

Boeing withdraws 2019 financial forecast, takes $1Bn hit, cashflow down 11%. Bloomberg estimates total cost will 10x this, predicts 737 Max out of service until October.

https://www.cbsnews.com/news/boeing-earnings-first-quarter-results-1-billion-hit-from-737-max-woes/

[Gabriel]

Now you're really confusing me. From 05:40:40 to 05:40:45. the column inputs exceed 10° back, while the actual pitch displacement never exceeds 5° ANU. Power remains at take-off setting. Thus the aircraft gains 100kts and exceeds Vmo.

Let's be factual. From 5:40:40 to 5:40:45 the control columns remain between 6 and 8 degrees. I think you mean between 5:40:24 and 5:40:30. During these 6 seconds the left control column moves between 10 and 12 degrees while the right control column moves between 7 and 9 degrees (it is the only zone of the plot where there is a persistent and clear split between the control column positions, don't know why).

Note that this period corresponds to the second activation of the MCAS, and corresponds to the point where the plane was most out of trim in the whole flight (in trim units that is, because at the end while the trim got close but didn't achieve the same extreme displacement, the speed was much higher so the effect of the trim was more powerful). During this second MCAS activation they make a long thumb-switch input which immediately stops the MCAS and brings the trim to a less out of trim (but still quite out of trim) position. After they release the thumb switch they use the cutout switches. So 5 seconds after they released the thumb switch the MCAS kicks in again but the trim doesn't respond. During all this process the speed remained below Vmo. Only after they cut the cutout switches the speed exceeds Vmo.

Other than these brief 6 seconds where one of the control columns exceeded 10 degrees by a little bit in the moment of worst trim displacement, both control columns remained below 10 degrees all the time. That is, until after the last MCAS activation. At that point they pulled them back to 14 degrees and at a point where they were doing well above Vmo. If they could pull the columns 14 degrees a well above Vmo and after the last MCAS had already kicked in, they certainly could have done the same at ANY PREVIOUS POINT and hence AT ANY PREVIOUS POINT they had elevator power and arm strength available to pitch up, had they attempted to do it. I am certain that if they had had the goal to pitch 25 degrees up and had tried it, they could have done it at any point before the last MCAS activation.

But then we have Mentour Pilot showing us how, in mistrim at Vmo+, he needs all his strength to keep the nose up and his FO can't move the stab trim wheel.

Ethiopian was at Vmo+ kts from 05:40:45 until beyond 05:43:15 when the electric trim is restored (presumably because the FO couldn't move the trim wheel).

It was at that speed because thrust remained at take-off setting, stab trim was stuck at 3 units (ANU) and pitch never managed to get above 8° and was occasionally negative (presumably due to extreme mistrim forces).

It was at that speed because they kept the pitch too shallow after take off and with take-of thrust. Reducing thrust would have reduced the speed at least initially but would have had some undesirable side effects. Pitching up would have been at least as effective, if not more, at reducing the speed and it would have had no undesirable side effect but a couple of desirable ones.

So, speed on elevator isn't working, we need to slow down to get manual control authority back, what else have we got? Oh right, power levers!

Speed on elevator works.

I am not so sure that Mentour wasn't able to pitch up any more. Certainly he was for most of the flight, since he keeps displacing the control column more and more against an increasing speed and an increasing nose-down trim.
Remember: In the video in its original form, he was simulation an initial unreliable speed and they call the memory items which included pitch 4 degrees, and only AFTER they have the trim runaway.
His goal was to keep 4 degrees. His speculation (that he edited it out in the 2nd release) was that the pilots might have been focused in applying and maintaining the unreliable speed items while fighting the trim at the same time. The first part of the sim session that was there in the 1st video is not there anymore, but you saw the FO calling UAS, 4 degrees, 80% (if I remember correctly) and Mentour applying that.

And, by the way, the FO never helped Mentour pull back. You still had about 100% more force available to apply on the columns.

For Ethiopian, the FDR plot is absolute proof that they could have pulled up at ANY POINT before the last MCAS activation. After that, speed on elevator would still work, you just needed help from the trim thumb switch.

[TeeVee]

So, speed on elevator isn't working, we need to slow down to get manual control authority back, what else have we got? Oh right, power levers!

CONGRATULATIONS!!!!!!!!!!!!!! once again, our resident einstein has cracked it long before the rest of the world.

of course he's done this amazing feat over the course of what, a month? and from the comfort of his desk, safely parked at sea level, and with access to all manner of reports, schematics, manuals, fcoms, qrhs etc etc etc.

and after all of this, he has decided (and must necessarily be correct) that it was all the pilots' fault. case closed. put the max back in the air at once and shoot any pilot that even comes close to fucking up again in this perfect aircraft desinged and produced by a perfect comapny with nothing but the best intentions...

[Gabriel]

TeeVee, that we discuss what these pilots (or other pilots that in the future face a similar situation) could have done to save their own lives does not mean that we are blaming them for not having done just that. End even less that we are exonerating Boeing for the crappy MCAS design.

[ATLcrew]

CONGRATULATIONS!!!!!!!!!!!!!! once again, our resident einstein has cracked it long before the rest of the world.

of course he's done this amazing feat over the course of what, a month? and from the comfort of his desk, safely parked at sea level, and with access to all manner of reports, schematics, manuals, fcoms, qrhs etc etc etc.

and after all of this, he has decided (and must necessarily be correct) that it was all the pilots' fault. case closed. put the max back in the air at once and shoot any pilot that even comes close to fucking up again in this perfect aircraft desinged and produced by a perfect comapny with nothing but the best intentions...

And remember, this forum is actually NOT about him, even though his by far the loudest voice here...

[ATLcrew]

TeeVee, that we discuss what these pilots (or other pilots that in the future face a similar situation) could have done to save their own lives does not mean that we are blaming them for not having done just that. End even less that we are exonerating Boeing for the crappy MCAS design.

Noted, thanks.

[TeeVee]

TeeVee, that we discuss what these pilots (or other pilots that in the future face a similar situation) could have done to save their own lives does not mean that we are blaming them for not having done just that. End even less that we are exonerating Boeing for the crappy MCAS design.

Gabe, it's one thing to say, "they could've or should've" but given the shyte they were faced with, laying blame at their feet over and over ad nauseum is just plain disgraceful, especially from an internet parlour talking no one. i would be far less offended if a real pilot said, hell, those guys killed themselves, or that they screwed up.

this is not AF447.

[Gabriel]

Gabe, it's one thing to say, "they could've or should've" but given the shyte they were faced with, laying blame at their feet over and over ad nauseum is just plain disgraceful, especially from an internet parlour talking no one. i would be far less offended if a real pilot said, hell, those guys killed themselves, or that they screwed up.

this is not AF447.

TeeVee, I am a real pilot, that doesn't make me any better except that I fit in your "acceptable" (or less unacceptable) category, but more importantly I have a strong curiosity to find out what pilots could possible have done different in a given situation, even when it is evident that a given set of pilots in a given circumstance that ended badly could not do it differently, otherwise they would have.

A lot of accidents were technically avoidable had the pilots reacted in specific different ways than they did. Even accidents where the fuse was lit by previous wrong actions of the pilots themselves, or by other circumstances. I would risk to say that that's the case in most fatal accidents.

Deeply reflecting on that makes you a better pilot, better prepared to react correctly to abnormal situations. And, done by the correct people (not me) enables industry-wide improvements in procedures and training.
That something can possibly done better or different doesn't mean blaming someone who, without the benefit of hindsight, did not do it. But for the next one that faces a similar situation, it should not be hindsight anymore.

Finding mistakes or opportunities and looking for ways to improve is not blaming. Maybe it is in Law, but it is not in the aviation industry and it is certainly not in Quality which is actually my area of professional development.

And that the pilots could have done something that saved the day DESPITE a crappy design, is not diminishing the problems of the design.

It is evident that human factors played a major role in these 2 accidents. Stress, fear, startle, tunnel vision, task saturation etc. are possible factors. It is also evident that training was an issue. Apparently the Ethiopian pilots were not trained for the MCAS malfunction other than by sending each of them a memo that hopefully they would read in their free time.

And sometimes, I just don't understand why a pilot did or did not do something.
In the last posts we have been discussing different possible methods that the pilots could have used to slow down or avoid gaining so much speed, which in turn would have allowed them to move the trim wheel manually. That's a moot point for the investigation of the cause of these accidents, since the pilots likely didn't even now or realized that the trim wheel could become impossibly hard at high speeds (combined with strong miss-trim and large elevator deflection to counteract it). In any event, the question could be why the pilots didn't know that? But, not as an investigation for the cause, but as lesson learned, it is perfectly valid to say that slowing down would have been a good idea and that it could have been accomplished in this or that way and these are the pros and cons of each.

Now, if you ask me about what these particular pilots of these particular accidents did (or didn't) that I really don't understand, it is not why they didn't pitch up or throttled back to slow down, it is not why they didn;t extend the flaps to stop the MCAS, it is not why they didn't use the cutout switches (in one case) or reconnected them (in the other). It is stop using the thumb switch. The thumb switch is an integral part of the pitch control and is used all the time (well, the little time that the pilots fly manually) to trim the stick forces out. To trim nose-up with the thumb switch should be a natural, automatic, not-reasoned response. Something that, in both accidents, actually worked when they did it. Until they stopped doing it.

Actually, I have a couple of hypothesis that still don't explain it but may go in that direction. In Lion Air it seems that the pilot that had kept the plane flying by applying nose-up thumb switch to counteract the nose-down trim inputs from the MCAS, transferred the control to the other pilot without telling him what he had been doing. In Ethiopian, I am starting to suspect that, when the last MCAS activation kicked in, they switched off the electric trim again to kill it, except that the plane was too much out of trim by then and that action disabled the MCAS but also the thumb switch. WHy do I suspect that? I really have no evidence, it is just an effort to invent a reason why/how, if they reconnected the cutout switches to be able to trim with the thumb switch, they didn't keep trimming with the thumb switch after 2 brief clicks.

Finally, the design was terrible. A single point of failure produced speed disagree, altitude disagree, flight director disagree, stick shaker disagree (shaking on the affected side) and repeated large automatic nose-down trim inputs, in a system that can become frozen when you try to fight it.

I cannot overstate how bad the design was. Still, I like that pilots that face a technical problem or a bad design, survive it. And these ones couldn't, but could have. It is worth finding out how.

[3WE]

CONGRATULATIONS!!!!!!!!!!!!!! once again, our resident einstein has cracked it long before the rest of the world.

of course he's done this amazing feat over the course of what, a month? and from the comfort of his desk, safely parked at sea level, and with access to all manner of reports, schematics, manuals, fcoms, qrhs etc etc etc.

and after all of this, he has decided (and must necessarily be correct) that it was all the pilots' fault. case closed. put the max back in the air at once and shoot any pilot that even comes close to fucking up again in this perfect aircraft desinged and produced by a perfect comapny with nothing but the best intentions...

Since we're having a zinger fest, I'm going with teevee today...It's Evan's tone that gets him in trouble (along with indications that he lives in a bubble with minimal appreciation for bike riding, Beech maneuvering and management of diving 737s, riding on any airline or even being a poor UAL gate agent, trying not to blow it on his/her SMART goals.)

"Why didn't the dumbass pilots simply power back?" Did Evan truly say that? Would it hold up in court? No...but it's basically what he said...

[Evan]

Finding mistakes or opportunities and looking for ways to improve is not blaming.

Actually, it is blaming, but not in the way TeeVee assumes. When pilot error is revealed, often there are people to blame who are not the pilots. We can and should blame the people who neglected to train and prepare them. We can and should blame the people who designed systems that could malfunction in a way that overwhelms a pilot's situational awareness and workload. We can and should blame the people who certified the plane in spite of this. Blame does not necessarily mean punishment however. Punishment is only called for if the blame involves a knowledge of wrongdoing and a willful intent to subvert safety with ulterior motives. In this case, I suspect the latter might be true.

TeeVee's assumption that my suggestions of pilot error is a condemnation of the pilots is tone deaf. I've repeatedly suggested that the design, when malfunctioning, results in tunnelling due to known human factors. I've also suggested that the procedure issued by Boeing after the Lion Air crash was flawed and even detrimental to recovery.

I am starting to suspect that, when the last MCAS activation kicked in, they switched off the electric trim again to kill it, except that the plane was too much out of trim by then and that action disabled the MCAS but also the thumb switch. Why do I suspect that?

I also think this. If switching the powered trim back on results in another uncommanded pitch event, they would conceivably react by switching it off again. At this point, they would be quite confused and disoriented.