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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 22nd Mar 2019, 15:37
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I would like to know why Boeing didn't install the "optional" AoA sensor fail light after Lion Air. Oh right - they're $80,000 each. Saved a penny!

I'd also like to know why any pilot who flew the Max didn't know about the MCAS (and knew immediately how to identify a failed AoA) after Lion Air.

It's not just one failure - it's a layer cake of failure.

Originally Posted by JRBarrett
I am at a loss to understand how Boeing engineers could not/did not foresee the dangers in their original implementation of MCAS.

These issues are allegedly addressed in the software update for the MCAS system, but how could such a flawed design have ever passed muster in the first place?
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Old 22nd Mar 2019, 15:54
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"Standard Boeing 737 Max Planes Are Not Equipped with A So-Called Angle of Attack Indicator"

This and another safety feature only available as expensive "options."

https://www.nytimes.com/2019/03/21/b...es-charge.html
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Old 22nd Mar 2019, 16:11
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Originally Posted by hum
I agree stall AoA varies with configuration, Mach # and others however, I donít think that, given all other values constant, weight changes AoA. Ie, a wing stops being a wing at the stall AoA, regardless of how much lift is demanded..
Well, it's true that stall AOA doesn't change with weight - but the AOA *required* for a given airspeed absolutely changes with weight - more than any other variable other than flap setting. (I am a senior flight test and simulator test engineer and do this stuff regularly. I think I can speak definitively.)

The aero equation for lift is this: Lift = 1/2 * Coefficient of Lift * density * speed^2 * Wing Area.
- In level non-turning flight, lift must equal weight.
- In turning or accelerated flight, lift must equal weight * load factor.
- Coefficient of lift is (in most wing designs) a nearly linear function of AOA, up until stall.
- Moving flaps/slats changes the coefficient of lift curve, so different values of CL-AOA exist for different configurations.

Therefore, AOA changes approximately linear with weight for a given speed. You need a fairly complex set of tables to know the expected AOA for all possible configurations, but the exact relationship is extremely clear.

This is why I assert that the average pilot will never be able to say "that indicated AOA is exactly correct ." With some experience, he can certainly say "I'm used to seeing this approximate AOA for a configured approach at this fuel weight." He can also certainly say "Wow, that AOA value is off-the-chart wrong." I think you're just adding to the mental complexity of flying without benefiting the average pilot.

On the other hand, the FMC can compute the expected AOA value from internal charts; it already knows the gross weight (as entered by the aircrew during nav mission planning); it knows the flap configuration and gear configuration. It would need either load factor (g's) (which is probably doesn't have) or angle of bank (which it does have), assuming you're not flying an airshow and doing big pushovers/pullups. It should then be able to figure an approximate expected AOA, and compare the measured AOA, and pop up an alert if there is a big (and sustained) mismatch. (You don't want to flag brief mismatches, because turbulence would trigger it, and it will never be correct below flying speeds like taxi or rollout.) So there's plenty of ways to use the onboard computing power more wisely than it is being used now, without burdening the pilot with basically irrelevant information.

Originally Posted by hum
I also agree that simply introducing an AoA indication in the cockpit of an airliner will not benefit crews without some education. However, AoA is a fundamental parameter, if it is displayed and obviously in error (deduced by crew education) then it could assist in fault finding. One of the key parts of UPRT (being introduced as mandatory in Europe for all new CommerciL licence training from Dec 2019) is AoA & G awareness. I believe it would be of huge benefit if commercial aircraft had AoA displayed and pilots were educated in its interpretation from day 1 of flying training.
True enough - but if a third-world flight crew has trouble with other basic skills, would showing them raw AOA really benefit them?

I suppose a good compromise is don't show AOA unless there's a miscompare - then (along with a very obvious miscompare notification) show the left AND right values right next to each other, not cross-cockpit.
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Old 22nd Mar 2019, 16:26
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Originally Posted by bsieker
No, it's a terrible article because its only conclusion is "these pilots were idiots! I would have flown the airplane no problem!".

That is not only unhelpful, it is counter-productive in trying to make aviation safer.
s
It should by now be obvious that crews cannot be expected to handle this every time, and a system that relies on 100% human performance in case of a small technical malfunction simply is not acceptable.

Bernd
Bernd. By "every time" we are talking about a rare event but one that did happen. "Every time" a pilot suffers and engine failure on takeoff at V1 - a rare event, he is expected to handle it 100%. That is all we are saying really. Once again it is important to re-state that we don't know what happened on these two flights in any great detail and we await the full reports. What I have tried to do here in the last few days is explain how a 737 is capable of being flown in most all circumstances (not necessarily this exact one) and how it differs from pretty much any other modern plane in that computers are not at its heart. When the report is complete my guess is that there will be multiple factors at play which all contributed to a chain of events - as is so often the case. I will confess that I did not read the full article and will do so now to see where there is a suggestion that "some pilots are idiots" - I didn't pick that up first time around. My apologies.
Cheers
Y
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Old 22nd Mar 2019, 16:27
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Salute!
Can any MAX pilot out t here state whether the MEL covers MCAS please?
There ain't no piece of equipment for MCAS!!! GASP!

For the nth time, it is a software module in the FCC on one of the two cards there. Just like the EFS and now the SYDM boxes have migrated.
Computer chips and lines of code have replaced all the ropes, levers, pulleys and cables so many here brag about. And maybe too many here and in the media think there's a switch or ckt breaker for MCAS. There ain't. It's like a runaway aileron actuator. You can turn it off by disabling the hydraulic system, but what else do you loose?

And speaking of what else you loose, a great example of not turning off the main supply for auto power steering and brakes happened with ruwaway throttle. The fatal accident might have, and should, have been prevented by using what was available and not turning off the motor supplying the power steering function. A well known auto magazine reporter duplicated the malfunction and simply pressed hard on the power braking pedal. It took a half a mile, but he maintained control and once he got real slow he could turn off the motor and maintain enough control to stop. Brakes were shot, but he was alive.

To be fair, I am not sure exactly what I would have done in the first two minutes of the 610 scenario. I would not have thought the trim system was my main problem. If my wheel electric switch kept working, I would have kept going and prolly slowed down once flaps were up. Hell, I could look around, feel the airframe and was pretty sure the shaker was a malfunction. I would deal with that pesky trim later. After another minute of dueling with the trim I would be pretty sure the system was FUBAR and turned off the power to the motor before looking up any more procedures. Plane is flying O.K. on 75% power or whatever, and I can crank that trim wheel 50 times to get back to what we need for hands off controls.

I have only had two or three peacetime "problems" just after takeoff, and the jet was not completely out of control. For those who haven't seen it, this one was the worst.



Surprise!


Gums sends...
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Old 22nd Mar 2019, 16:47
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Gums is right, too many "pilots" think their aeroplane is made up of bits as per the pilots tech manual. The tech manual is written to explain how the system works, rather than actually what is there.
To explain:
some time ago I would regularly fall out with one of our trainers on the simulator. He would insist that the electrical system was made up of bus bars as in a lump of metal with things attached. In fact the mythical bus bar depicted in the training manual did not exist per say. The components (things) were attached to the electrical system via their own feeds and those feeds were controlled by system logic giving the impression of being attached to a bus bar. This meant that the logic was/is perfectly capable of isolating individual faults and or resetting other components(things).

This should be made clear during ground school, in that the aeroplane manufacturer knows their aeroplane. This means if the QRH calls for a resets without caveats, the pilot should do as per the QRH and NOT try to outthink the system. I know this goes against the grain for those used to the "old" way of doing things but design has moved on.
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Old 22nd Mar 2019, 17:21
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Reference the news article that I referred to, I did not finish reading it and realise now it contains some comments about "foreign" pilots. That is so far from my own position that I can only apologise for providing the link to the article. Having spent most of my life flying with and training pilots from all over the world I could not agree with that contention. This issue has nothing to do with foreign pilots - foreign to whom? USA in this case I think he means. I am a foreigner to someone from China I guess.
The quality of pilots has nothing to do with their ethnicity. I wish to make that very clear. The quality of pilots from anywhere is down mainly to the way they are trained and regulated.
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Old 22nd Mar 2019, 18:04
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Originally Posted by yanrair
Bernd. By "every time" we are talking about a rare event but one that did happen. "Every time" a pilot suffers and engine failure on takeoff at V1 - a rare event, he is expected to handle it 100%. That is all we are saying really. Once again it is important to re-state that we don't know what happened on these two flights in any great detail and we await the full reports. What I have tried to do here in the last few days is explain how a 737 is capable of being flown in most all circumstances (not necessarily this exact one) and how it differs from pretty much any other modern plane in that computers are not at its heart. When the report is complete my guess is that there will be multiple factors at play which all contributed to a chain of events - as is so often the case. I will confess that I did not read the full article and will do so now to see where there is a suggestion that "some pilots are idiots" - I didn't pick that up first time around. My apologies.
Cheers
Y
Someone used an interesting word the other day to describe how erroneous MCAS activation is different from an engine failure at v1. The latter is immediately obvious, it is trained for ad nauseam, and it is briefed before every takeoff. Terefore this is an item where we can and must expect near 100% performance. But the former is "insidious". It is not nearly as clear-cut, since other system will repeatedly trim the airplane as well, and a racket of other warnings and noises is also going on. It isn't one (sometimes literal) bang like an engine failure, and you are also not primed for it, because it is not briefed every time. And it is also not acceptable because there are ways to do it better! Rejected takeoff is dictated by raw, high-kinetic-energy physics, and not a lot can be done to get around that.

But most importantly, we know now that not all pilots will handle it well, and to say that only third-world pilots will ever get it wrong is "holier-than-thou"-hubris and no better than "Rep. Sam Graves (R-Mo.)" in the AOPA article.
(EDIT: just read your reply, and don't want to imply that you said or meant anything like that.)

As to "pilots are idiots", I was paraphrasing. What he said a couple of times, though, was "why didn't they simply do x?", which can only be said with hindsight (knowing the actual outcome, and only now knowing the correct solution), and is also arrogant, condescending and serves no purpose other than to feel smugly superiour.

Bernd

Last edited by bsieker; 22nd Mar 2019 at 21:15. Reason: typo.
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Old 22nd Mar 2019, 18:09
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Originally Posted by BrandonSoMD
True enough - but if a third-world flight crew has trouble with other basic skills, would showing them raw AOA really benefit them?

I suppose a good compromise is don't show AOA unless there's a miscompare - then (along with a very obvious miscompare notification) show the left AND right values right next to each other, not cross-cockpit.
I could hardly agree more, although it is also not limited to third-world pilots. I still contend that the AF447 pilots would not have benefited from an AoA indicator, either. I detailed that in another post which got deleted. It boils down to "none of the available instruments made any sense, why would they have believed an additional one, which would have shown an unbelievable value (40į) anyway."

Bernd
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Old 22nd Mar 2019, 19:23
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You are correct is stating that there is no "piece of equipment for MCAS" on the B-737 -8/9 MEL Rev. 1 dated 01/17/2018 (MMEL Ref. fsims.faa.gov) for MCAS, either under ATA 22 or 27. However, MMELs do cover many "distributed" FUNCTIONS. (As you describe alternatively as "migrated".) Even though there is not a single "box" or "piece of equipment", there can be MEL relief if specified, given that applicable (M) & (O) items are complied with. MCAS would likely qualify as distributed FUNCTION.
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Old 22nd Mar 2019, 19:25
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This should be made clear during ground school, in that the aeroplane manufacturer knows their aeroplane. This means if the QRH calls for a resets without caveats, the pilot should do as per the QRH and NOT try to outthink the system. I know this goes against the grain for those used to the "old" way of doing things but design has moved on.
This brings up an interesting point: If it is -not- in the QRH what then?

Reports suggest that the Lion air crews (both flights) might have been trying to find a match for their situation in the QRH and other manuals. The third pilot on first flight ultimately suggested the trim motor cutouts, not clear if this was before or after he got the large book from his carry on.

One theory is that some crews are trained/held to tight observance of SOP and any actions outside of those are strongly discouraged. This is good as long as the SOP can cover every eventuality, which of course they cannot.

Is it possible the Lion air accident crew did not follow the trim runaway procedure since it was not an exact match for what they were seeing and/or were afraid of consequences if they did and it was later deemed to be not following SOP?

Could this fear have influenced how the prior crew wrote up the incident?

Point being that system knowledge can be vital for undocumented cases, in addition to knowing the procedures understanding what they do and possible side effects is important since it allows problem solving in situations -not- in QRH or other sources.

In the Lion air MCAS case knowing for sure that the cutout switches would work -and- confidence that they could manage the aircraft after they were used might have saved the day.

Really too early to extend to Ethiopian case since not known (to public at least) how similar the cause(s) were.

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Old 22nd Mar 2019, 20:34
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Originally Posted by bsieker
But most importantly, we know now that not all pilots will handle it well, and to say that only third-world pilots will ever get it wrong is "holier-than-thou"-hubris....
Well, we can't expect ANY pilots to handle it well, if their differences training was limited to a one-hour session on an iPad that didn't even mention MCAS.
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Old 22nd Mar 2019, 20:37
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A little Occam's razor:

Automation is simply nowhere near good enough to replace well trained, remunerated, rested and motivated pilots.

That the incessant cost cutting preferred by both airline management and manufacturers alike is flawed.
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Old 22nd Mar 2019, 20:54
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Originally Posted by Rated De
A little Occam's razor:

Automation is simply nowhere near good enough to replace well trained, remunerated, rested and motivated pilots.

That the incessant cost cutting preferred by both airline management and manufacturers alike is flawed.
Ockham might opine: Automation is good enough to replace average, insufficiently-trained, underpaid, overworked and thus no-longer-motivated pilots. The latter seem increasingly to outnumber the former.

Which is why pilots will soon (probably sooner than they expect) go the way of elevator operators. That may be sad in vaguely nostalgic fashion but will decrease seat costs, ticket prices and fatalities per million flights.
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Old 22nd Mar 2019, 21:21
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Originally Posted by BobM2
Rananim, a faulty AOA that would activate MCAS would produce a continuous stick shaker at rotation, not on flap retract. Why would any right-thinking pilot ever attempt to retract flaps & continue the flight with an active stick shaker, even if unaware that MCAS exists?
That one is esay, you cross check the 3 airspeed indicators, thrust, performance and attitude to determine if the stickshaker is real or false.
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Old 22nd Mar 2019, 22:05
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Originally Posted by Turbine70
What we can only conclude as a design flaw requires recurring RTO above Vr?

Wrong focus.
No, not wrong focus. Nobody is advocating RTO above Vr unless unlimited runway is available. A faulty AOA could give a stick shaker on take-off rotation in any airplane whether it has MCAS or not. The point I am trying to make is if the airplane is climbing & accelerating normally & stick shaker is on one side only, it is an AOA failure & not a valid stall warning. The correct response to this is to return & land the airplane. Get it fixed! You don't accelerate, clean up the flaps & try to continue the flight with an active stick shaker as Lion Air did on two occasions, only one of which was successful (barely).
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Old 22nd Mar 2019, 22:24
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Originally Posted by infrequentflyer789
Yup. From that same data source (and wishing vbulletin did tables):
737 NG: >20 years, >7000 built*, 20 hull losses, 591 dead
737 MAX: <3 years, ~350 built, 2 hull losses, 346 dead
So, if it's the crews or the airlines and not a problem with the plane, how do you explain the (order of magnitude at least) difference in crash rate?
On the surface that is an interesting observation, however it is the result of working with unequal population sizes and looking at temporal processes. Safety of a system is judged by exceptional events, losses in aviation. overall, historically loss rate has loosely followed a curve similar to long term average costs in economics, a broad U shape. initially there is a potential elevated risk from unknowns in a new system (airline, aircraft, route, operation etc..) which is mitigated by the control loop of the system. After an extended period of time new factors will come into play, which may elevate risk, loss of corporate knowledge, structural fatigue, ageing effects, apathy etc. these are also affected by the overall system response which should improve over time, and it does to an extent, SSID, SMS etc, but the underlying issues are non linear, and the system response is also non linear. Responses hardly ever are exactly correct and without new risks and unintended consequences.

Pretty much, systems are non linear. Estimates based on largely different samples are only correct in say QA sampling, and even then it comes with interesting maths due to uncertainties.

The NG didn't make headlines on safety with its introduction, however there were considerable fatalities from the start for various issues, and the fatality rate then reduced. The losses occurred in the noise of other events, and did not raise eyebrows. in more recent time, we continue to see over runs, loss of control, and similar crew related matters increase on the NG. The A320 started with a lousy run of losses, most due to knowledge issues with the crew related to the automation functions. the A320 loss rate continued to be managed, but there are still wild card events that occur to this day, including loss of control, CFIT and other odd events.

Both of the airlines involved with the most recent events have considerable track records with accidents, all of them raising questions on system integrity. For the regions that they operate in, at least in Africa, ET is one of the better performers. In Indonesia, safety records are always of concern, and JT has had its share of events and losses, which given its size of operation is probably not far from the average in the country. Indonesia like Africa has elevated operational risk factors, that even if comparative operational standards exist would probably lead to more incidents of the type that are most common there, overruns and offs of the runway. Loss of control events have occurred with various aircraft types in the region, for a multitude of reasons, crew turning off the attitude platforms, severe weather encounters...

The question on the Max is why did apparently trained crew not recognise and action a simple procedure in the events. Stab cut out has been fitted since the 40's, when stabs were the solution to high speed flight trim changes. Cutout is not a new device, nor is the problem of uncommanded stabiliser trim changes. So with the Max, what is the reason the crew didn't recognise the need to do a simple action to save the day? The concurrent stall warning would appear to have had a strong influence on the cognitive capabilities of the crew on the day. The revised event information of the JT aircrafts prior flight suggest that on the day that crew also needed additional input to successfully undertake corrective action. The CVR info on JT610 starts to suggest that the crew did attempt to manage the event in a calm manner, but with that process, the hand over of the flying duties from the capt to the copilot had a down side, the captain had been responding to the uncommanded trim, the copilot was not successful in doing the same and the flight path was promptly affected. It is indeed unfortunate that the captain following CRM best practice training principles takes action that appears to have had severe consequences. If the captain had recognised the trim problem consciously, cutout would have been an appropriate action. The copilot was handed an aircraft with the problem, and it is quite possible (unknown at the moment) that the captains successful reactions to the trim problem were subconscious, and that it was being managed so was not communicated at the time of the transfer to the copilot. That point is going to need consideration for any real longterm improvement in problem cueing, where the comprehension of the crew of the actual status is critical. Crew SA is paramount, and what appears to be 3 cases so far had problems in this area.

I don't think that these operators are unique in the issue of SA at all.

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Old 22nd Mar 2019, 23:02
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Originally Posted by Ian W
---snipped--
Would you really let trim carry on monotonically trim down 2.5 units every 5secs and not switch it off? l can only assume that you would. It is really immaterial why the trim was operating it could be a now dead rodent chewing through an electric cable, you just want the trim to stop and two switches that have been there forever allow you to do that. I am sure that Boeing is aghast that their NNCs for trim runaway were being read in such a contracts lawyer fashion. Perhaps they should review the semantics of all memory items and NNCs/checklists and any training that reinforces those limiting semantics.
The Lion Air crews DID NOT KNOW how many units or even how long this goblin would trim. They didn't even have 10 seconds to observe the trim wheel amidst all the warning. To them, what happened to AC was exactly like what was reported/read in the pre-flight briefing: "STS running the wrong direction due to speed difference". As reported on the Lion Air's A-SHOR:


The conflicting data's [ALL INDICATORS were out of whack - previous flight at least the SIC's indicators were still valid, but not this one], perhaps observing the surrounding, rummaging through the QRH, communicating with the ATC, etc..., were all conspiring to overload their mental faculties and sensory perception. And, to top things off, they didn't have the luxury of having a dead head sitting on the jump seat helping to observe and analyze what's going on.

On the preliminary report, CAPT and/or FO of the previous flight apparently had failed to mention the stick-shaker condition and the NNC for runaway trim they'd performed to overcome what thought to be the STS trim going the wrong way. The last few facts are very much what makes the hole in the Swiss cheese lined up.

Last edited by patplan; 22nd Mar 2019 at 23:07. Reason: clarity
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Old 22nd Mar 2019, 23:07
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I'm thinking that the JT610 P1 retrimmed completely from each MCAS excursion, but P2 did not allowing the nose down trim excursions from MCAS to accumulate while P1 was head down in the manual - which had no information on MCAS.

​​​​​​Will the CVR, once released, show whether P1 communicated to P2 what P1 was doing with trim before handing over control?

Remember also that stick shaker was adding workload.

We now know that a faulty AoA will both trigger shaker and MCAS once at a safe height where flaps are normally retracted and more thorough diagnosis of the situation can begin, but then they were handed a new problem.

​​​​​
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Old 22nd Mar 2019, 23:21
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Originally Posted by Ian W
How about the NNCs in all 737s for Runaway Trim? oh of course it is not 'runaway' as it is only repeated (reads from dictionary) nose down trim, so I will let the Stab Trim fly me into the ground rather than switch it off.

Would you really let trim carry on monotonically trim down 2.5 units every 5secs and not switch it off? l can only assume that you would. It is really immaterial why the trim was operating it could be a now dead rodent chewing through an electric cable, you just want the trim to stop and two switches that have been there forever allow you to do that. I am sure that Boeing is aghast that their NNCs for trim runaway were being read in such a contracts lawyer fashion. Perhaps they should review the semantics of all memory items and NNCs/checklists and any training that reinforces those limiting semantics.

Yes recognizing the trim issue is the heart of the matter. That was exactly my point. You cannot make this into "switch off the AP and fly the plane"-scenario. A pilot with poor manual flying skills but being able to identify the issue does much better than a skilled flier who isn't able to identify the issue.

It doesn't help you to switch off AP and AT and stabilize things by flying "power and pitch". You can't because you don't achieve a stable pitch.

So hence my real point, the challenge: Show me that up until six months ago anyone suggested making "stab trim cutout" part of a "disengage auto and fly the plane" if you don't have a clue what the issue is.

The "should they have been able to catch on to the trim issue?" discussion has been done ad nauseam. In my personal opinion the only way to hypothetically get the truth there would be if you could find 20 average pilots who had been in coma for the last six months and put them through a surprise sim scenario replicating an actual MCAS-misfire.
Then we would know how the average pilot would have done.What people with all the facts are now convinced they would have done is not relevant evidence to me.

I bet that if you asked the average px if they were confident that they'd get a life jacket on in case of a water landing landing the vast majority would say yes. They've seen the briefing a gazzillion times. How hard can it be?

Yet we know how many out of a 150 px in the "Sully flight" actually managed to put on a life jacket properly waist strap and all. Was it a three digit number? Was it a two digit number?
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