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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 4th May 2019, 12:40
  #4861 (permalink)  
 
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Ad nauseam

737 Driver,
Ad nauseam is a Latin term for argument or other discussion that has continued to the point of nausea. … indicating that the topic has been discussed extensively and those involved have grown tired of it.

Repetition does not change the accuracy or value of a statement or argument.
People, aviation, the world is not absolute, thus by considering the in-between ‘grey’ area opens the possibility of identifying something to learn. It is up to us to take these possibilities, accept that there is always something new to learn.

Avoid ‘what is’, and consider ‘what might be’; accept that no single view is absolute, not applicable to all situations, particularly those which you did not attend.

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Old 4th May 2019, 12:52
  #4862 (permalink)  
 
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Originally Posted by alf5071h View Post
737 Driver,
Ad nauseam is a Latin term for argument or other discussion that has continued to the point of nausea. … indicating that the topic has been discussed extensively and those involved have grown tired of it.

Repetition does not change the accuracy or value of a statement or argument.
Perhaps it's worth noting that repetition and practice are core drills behind many learned skills, including aviation. It seems that certain reminders are very much in order here.

"People need to be reminded more often than they need to be instructed." - Samuel Johnson
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Old 4th May 2019, 13:03
  #4863 (permalink)  
 
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Originally Posted by LEM View Post
Fact is that even if your brain is short circuited by fear of death, that's exactly in those moments that pilots should be real pilots, I mean resource to INSTINCTS, BASIC INSTICTS.
A "pilot" who hears the tremendous noise of 500 knots (!) and doesn't even touch those tho things in the middle of the pedestal (also called trust levers) to pull them back.... well, should be doing another job (and I put it nicely)....
If you bothered to read the preliminary report you would have seen that they were not at 500 knots (!!!????!!!!). They only reached 500 knots immediately before impacting the ground, after diving for 20 seconds following the final MCAS activation.

Before that however:

"From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units. During this time, aft force was applied to the control columns which remained aft of neutral position. The left indicated airspeed increased from approximately 305 kt to approximately 340 kt (VMO). The right indicated airspeed was approximately 20-25 kt higher than the left."

Which is consistent with the FDR IAS trace.
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Old 4th May 2019, 13:20
  #4864 (permalink)  
 
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Originally Posted by PaxBritannica View Post
The first crew 'happened' on a solution. .
The crew did not happen on anything, It was a jump seat pilot from a different airline that told them what to do and saved the day.
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Old 4th May 2019, 13:38
  #4865 (permalink)  
 
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Originally Posted by James7 View Post
The crew did not happen on anything, It was a jump seat pilot from a different airline that told them what to do and saved the day.
I believe that's a pretty good definition of 'happening on a solution'. They tried other things unsuccessfully and then tried the suggestion of a third party, and it happened to work.
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Old 4th May 2019, 13:39
  #4866 (permalink)  
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Originally Posted by HarryMann View Post
Forgive me but I don't believe this has been asked or answered before, so maybe I'm missing the basics but...

At stick shaker upon or immediately after take-off

Would raising the flaps be expected even when past V2 and apparently accelerating and climbing normally.
Surely an immediate return might be anticipated whilst I acknowledge a desire to cleanup and find a stable and mentally comfortable flight regime.

So surprised not to see this action directly criticised... I can see theres a conflict or choice between wanting adequate speed/thrust setting and sticking with a speed limiting flap setting (i assume).
Well, Yes & No.

The crew have 3 independent IAS indications, and the AOA information in passing by the lower limit speeds on the IAS tape. The AOA is incorrect, and that is triggering an erroneous correction to the Capt's IAS and triggers the disagree messages, the AOA already triggering the stall warning erroneously. The crew understand the aircraft is flying, and a cross check of power/attitude as well as comparison of the Capt/FO and the integrated standby would indicate that the Capts display is erroneous, and using the other sources, cleaning up would be possible. it is also possible that the crew were following established routine and raised the flaps. Once that was done the headaches multiplied rapidly. Either scenario is quite possible. Frequently, a crew will raise the gear after takeoff following a tyre failure or other issue that would contraindicate that procedure. We do tend to follow entrenched routine, even though such routines can be quite easily interrupted.


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Old 4th May 2019, 13:40
  #4867 (permalink)  
 
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Originally Posted by 737 Driver View Post
Which is precisely why I and others have stated ad nauseum that when a pilot is presented with an undesired aircraft state, ambiguous warnings, or loss of situational awareness, they must be able to, at a minimum, Turn off the magic, Set the pitch, Set the power, Trim the aircraft, Monitor the performance, and Move to a safe altitude, i.e. FLY THE AIRCRAFT. This is the default response to any emergency or non-normal situation when a pilot is unclear as to what he/she should do next. And yes, it is a trainable response.

Performing these actions is no more difficult than executing the procedures for an engine fire/failure at V1, and we should not expect any less from a trained and competent commercial flight crew.
With respect-

You were the only pilot that responded to what "would you do" that maintained the flying pilot position. You gave very little tasks to the non flying pilot and you even did not acknowledge the input that they would have given you. Your feed back was of a one man crew.

Both others that replied handed over to the FO to fly, I expect as they had the accurate instruments not just air speed but pitch - the pilots pitch was incorrect!

Again the pilots pitch was incorrect.
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Old 4th May 2019, 13:40
  #4868 (permalink)  
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I recall a mention of the electrical motor running while clutches changed the drive from one authority to another. Is the stopping of the wheel reliant on a clutch slipping? It seems from this thread that the smaller diameter wheel might be a bit of a challenge.

I asked before, but does anyone know how long the motor runs on for? I find it hard to believe it is powered down after every single pulse of the thumb switches, so I assume a lag in the power-down.
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Old 4th May 2019, 13:55
  #4869 (permalink)  
 
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Originally Posted by Loose rivets View Post
I recall a mention of the electrical motor running while clutches changed the drive from one authority to another. Is the stopping of the wheel reliant on a clutch slipping? It seems from this thread that the smaller diameter wheel might be a bit of a challenge.

I asked before, but does anyone know how long the motor runs on for? I find it hard to believe it is powered down after every single pulse of the thumb switches, so I assume a lag in the power-down.
is a brushless motor, therefore it will be powered on and off for every blip. Practically not lag
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Old 4th May 2019, 14:14
  #4870 (permalink)  
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Originally Posted by 737 Driver View Post
Performing these actions is no more difficult than executing the procedures for an engine fire/failure at V1, and we should not expect any less from a trained and competent commercial flight crew.
Ordinarily I would agree, however, the problem here is that there was a fundamental SA failure in the process of all of these events.

In the flight prior to JT610, the crew did not initially comprehend what was happening, perception was initially missing. The crew did eventually recover from that state when there was intervention by the 3rd flight deck person drawing attention to the trim behaviour. SA-1 Perception Failure. Thereafter the crew went for a 2 hour transit with the stick shaker running in the background...

On JT610, the crew had an SA-1 Perception failure to start with as well, and arguably detected the uncommanded stab motion and thereafter had an SA-2 Comprehension failure, which occurred with the handover to the FO of the aircraft while the Capt commenced further investigation. The Captains handover resulted in the effective termination of intervention from corrective trim input by the FO. Arguably there was an SA-3 type failure at the same time, as the Capt did not project forward the implications of not continuing the intervention of the trim input by MCAS, which led directly to the aircraft being so far out of trim that the dark knowledge of the potential for the trim being defeated without a specific manoeuvre to unload the stab was not realised. The FCOM is underwhelming on the subject, and the Capt ran out of ideas, time, altitude and elevator authority promptly.

ET had some information provided per the EAD, however, the crew had SA-2 failure once again.

Training of runaway stab is not a common item, and training for severe out of trim cases is effectively non-existant, and the FCOM hardly suggests that the matter may end up being critical for recovery time/altitude. If the crews are to be expected to respond appropriately, then sufficient knowledge and training is necessary so that the crew can make a decision based on recognition (RPDM) or if time permits, by analysis. As the crew were still ill informed that control loss was quite possible, and that a recovery would need a procedure that was not meaningfully described and not trained, it is difficult to shoot the messenger, the crew in question.

The SA failures that occurred here occurred in a period of dynamic operations and with high levels of stress on the decision makers. The truth is that people will respond differently with the set of cues that were in play on these occasions, and training to improve the likelihood of a desirable outcome is necessary. Keeping pertinent information from the flight crew was unhelpful, and the FCTM discussion on out of trim events fails to indicate the criticality of the situation, one that raises questions on the basis of certification of the aircraft in the first place.

The crew did try to fly the plane, they didn't recognise the problem, they didn't comprehend what the situation was promptly, and when breaking the manual trim process they did not project the state forward as a result of that action, due to inadequate information and training. Were they flying the plane? they were, but they didn't know they had brought a knife to a gun fight.

The FCTM is a bland understatement of a potentially catastrophic situation.
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Old 4th May 2019, 14:27
  #4871 (permalink)  
 
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Originally Posted by 737 Driver View Post
Again, no evidence from either of these accidents or from historical data that the electric stab trim motor could stall under load. The matter of the electric trim inhibition discussed in the link above is a completely separate issue. That inhibition prevents main electric trimming (pilot actuated) into a certain region of forward trim, but it does not prevent the use of electric trim to move out of that region.

All this being said, one of the causal factors of these accidents is that the pilots let the aircraft so far out of trim in the first place. It is absolutely clear from the data (both ET302, and both LA610 flights) that the pilot actuated stab trim stopped and reversed the MCAS trim input every time it was used. As powerful as MCAS was, it could not overcome the strength inherent in the Captain's left thumb - if he had chosen to use it.
"No evidence" is a commonly used phrase used to justify all manner of absurdity (usually by politicians). The absence of evidence does not rule in or rule out anything.

"It is absolutely clear from the data (both ET302, and both LA610 flights) that the pilot actuated stab trim stopped and reversed the MCAS trim input every time it was used. As powerful as MCAS was, it could not overcome the strength inherent in the Captain's left thumb" It is not absolutely clear at all. The FDR does not track the thumbswitch position as far as I know. Thus, it cannot be said with certainty that there were not additional electric trim up inputs that had no effect. Your assumption seems to be based on the accuracy of Boeings publications. I do not think that any pilot, even a very bad pilot, would not make further electric trim up corrections under the circumstances. For these reasons there remain doubts in my mind. In the case of ET302 it seems the crew reactivated electric trim in desperation... following that action it is difficult to believe that they did not do so to apply constant electric trim up via the thumb switch. It is a puzzle what actually happened, but unless you KNOW what the pilots ACTUALLY did it is mere speculation rather than being "absolutely clear".
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Old 4th May 2019, 14:55
  #4872 (permalink)  
 
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Originally Posted by 737 Driver View Post
All this being said, one of the causal factors of these accidents is that the pilots let the aircraft so far out of trim in the first place. It is absolutely clear from the data (both ET302, and both LA610 flights) that the pilot actuated stab trim stopped and reversed the MCAS trim input every time it was used. As powerful as MCAS was, it could not overcome the strength inherent in the Captain's left thumb - if he had chosen to use it.
What do you make of this from ET:

05:40:27 - the Captain advised the First-Officer to trim up with him

Bearing in mind preceding it is an ineffective (in timing and duration compared to 1st MCAS input) period of manual ANU trim, and following it is a period of manual trim that both interrupts the 2nd MCAS input, is constant/continuous and reverses it (but doesn't reverse the first MCAS input).

It sounds (to this non-pilot engineering type) awfully like the Captain's left thumb (or it's switch) does not have the Captain's confidence, and not at all like he has just not "chosen to use it".

Or, put another way, under what circumstances as a 737 driver would you ask your co-driver to "trim up (or down) with you"? If the answer is "don't know any circumstances " or "would never do that", then WTF was going on in the ET cockpit to trigger that request?
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Old 4th May 2019, 15:11
  #4873 (permalink)  
 
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Originally Posted by infrequentflyer789 View Post
What do you make of this from ET:

05:40:27 - the Captain advised the First-Officer to trim up with him

Bearing in mind preceding it is an ineffective (in timing and duration compared to 1st MCAS input) period of manual ANU trim, and following it is a period of manual trim that both interrupts the 2nd MCAS input, is constant/continuous and reverses it (but doesn't reverse the first MCAS input).

It sounds (to this non-pilot engineering type) awfully like the Captain's left thumb (or it's switch) does not have the Captain's confidence, and not at all like he has just not "chosen to use it".

Or, put another way, under what circumstances as a 737 driver would you ask your co-driver to "trim up (or down) with you"? If the answer is "don't know any circumstances " or "would never do that", then WTF was going on in the ET cockpit to trigger that request?
Very good point!
i would also ask to the experts, what the FDR records? The thumb switch? The manual command to the brushless motor? Or the effective running of the motor?
Furthermore, since the MAX was the first aircraft with MCAS which agency should oversight the FDR signals recording? Spoilers are FBW, MACS is lingering in the background... how difficult will be for investigators to interprete recordjngs?
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Old 4th May 2019, 15:36
  #4874 (permalink)  
 
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Originally Posted by Bend alot View Post
With respect-

You were the only pilot that responded to what "would you do" that maintained the flying pilot position. You gave very little tasks to the non flying pilot and you even did not acknowledge the input that they would have given you. Your feed back was of a one man crew.

Both others that replied handed over to the FO to fly, I expect as they had the accurate instruments not just air speed but pitch - the pilots pitch was incorrect!

Again the pilots pitch was incorrect.
With respect -

As prelude, we need to correct one misunderstanding here. There was nothing wrong with the attitude indicators. The only manner in which the Captain’s pitch was incorrect or not was whether he established the correct pitch or not on his fully functioning attitude indicator.

There is no single right answer to this malfunction. Much depends on how quickly the crew perceives what is actually transpiring, what is working, and what isn’t. The major test of what responses were acceptable is whether those actions ultimately resulted in the safe landing of the aircraft.

The setup for this scenario was what would I have done if I were placed in the Ethiopian Captain’s position. May I remind you that he was given not only a malfunctioning aircraft but also a 350-hour First Officer? One of the important decisions a Captain must make, once the situation is stabilized, is to designate the flying and non-flying pilot. Yes, with a reasonably experienced First Officer, it would have been prudent to designate that person as the flying pilot once it was determined that he had the better instruments. However, it should be stated that there are certain real challenges to flying an aircraft with an AOA that is generating an erroneous stall signal due to the various ancillary system effects (I won’t detail them here, so you just need to accept my word on that). Unless this particular 350-hour FO had previously demonstrated to me that he had strong hand flying skills, then it is very likely that I would have continued to fly the aircraft for much of the remaining flight.

Last edited by 737 Driver; 4th May 2019 at 16:00.
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Old 4th May 2019, 15:44
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Originally Posted by wheelsright View Post
"No evidence" is a commonly used phrase used to justify all manner of absurdity (usually by politicians). The absence of evidence does not rule in or rule out anything.

"It is absolutely clear from the data (both ET302, and both LA610 flights) that the pilot actuated stab trim stopped and reversed the MCAS trim input every time it was used. As powerful as MCAS was, it could not overcome the strength inherent in the Captain's left thumb" It is not absolutely clear at all. The FDR does not track the thumbswitch position as far as I know. Thus, it cannot be said with certainty that there were not additional electric trim up inputs that had no effect. Your assumption seems to be based on the accuracy of Boeings publications. I do not think that any pilot, even a very bad pilot, would not make further electric trim up corrections under the circumstances. For these reasons there remain doubts in my mind. In the case of ET302 it seems the crew reactivated electric trim in desperation... following that action it is difficult to believe that they did not do so to apply constant electric trim up via the thumb switch. It is a puzzle what actually happened, but unless you KNOW what the pilots ACTUALLY did it is mere speculation rather than being "absolutely clear".
The DFDR traces show not only pilot and automation inputs on separate tracks, they also show whether the stab moved in response. There is even one example where MCAS is shown trying to make an input but the stab does not move because the stab trim switches were in the cutout position. Otherwise, every time that either the pilot or the automation made a stab trim input, then the stab moved as one would expect. I do not know whether the DFDR picks up the pilot trim signal directly from the switch or from somewhere else, but there were plenty of pilot inputs that corresponded to a stab movement. To conclude that the yoke trim switch suddenly stopped working requires a much greater leap of faith than a conclusion that it was used ineffectually.
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Old 4th May 2019, 15:50
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Originally Posted by infrequentflyer789 View Post
What do you make of this from ET:

05:40:27 - the Captain advised the First-Officer to trim up with him

Bearing in mind preceding it is an ineffective (in timing and duration compared to 1st MCAS input) period of manual ANU trim, and following it is a period of manual trim that both interrupts the 2nd MCAS input, is constant/continuous and reverses it (but doesn't reverse the first MCAS input).

It sounds (to this non-pilot engineering type) awfully like the Captain's left thumb (or it's switch) does not have the Captain's confidence, and not at all like he has just not "chosen to use it".

Or, put another way, under what circumstances as a 737 driver would you ask your co-driver to "trim up (or down) with you"? If the answer is "don't know any circumstances " or "would never do that", then WTF was going on in the ET cockpit to trigger that request?
There is abundant information here to show that this crew was absolutely overwhelmed by the circumstances they faced. There are many, many head scratchers that simply defy explanation if your going in assumption is that the crew was in control of the situation. They were not. Rather, the situation was clearly in control of them. So you must pardon me if I do not attempt to provide a rational explanation for many of their actions.
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Old 4th May 2019, 15:58
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Earlier I was comparing Boeing's MCAS with Volkswagen's emissions test defeat device. I found this old New Yorker article, from 2015, hypothesizing how Volkswagen may have got there:

https://www.newyorker.com/business/c...swagen-scandal

They say it may not have necessarily been an explicit management decision saying "let's cheat", but many small incremental changes that individually didn't seem a big deal (normalization of deviance):

If the same pattern proves to have played out at Volkswagen, then the scandal may well have begun with a few lines of engine-tuning software. Perhaps it started with tweaks that optimized some aspect of diesel performance and then evolved over time: detect this, change that, optimize something else. At every step, the software changes might have seemed to be a slight “improvement” on what came before, but at no one step would it necessarily have felt like a vast, emissions-fixing conspiracy by Volkswagen engineers, or been identified by Volkswagen executives. Instead, it would have slowly and insidiously led to the development of the defeat device and its inclusion in cars that were sold to consumers.
Initial reports mentioned that at least 30 Volkswagen managers were involved. And now, 4 years later, some of them have already been sentenced to jail time. So, at least in Volkswagen's case, it seems it was a bit more than just "normalization of deviance".
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Old 4th May 2019, 15:58
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Originally Posted by fdr View Post

The crew did try to fly the plane, they didn't recognise the problem, they didn't comprehend what the situation was promptly, and when breaking the manual trim process they did not project the state forward as a result of that action, due to inadequate information and training. Were they flying the plane? they were, but they didn't know they had brought a knife to a gun fight.
Which is precisely why, when presented with an undesired aircraft state, unknown or ambiguous malfunction, or a loss of situational awareness, the flying pilot must be ready and able to Turn off the magic, Set the Pitch, Set the Power, Trim the aircraft, Monitor the performance, and Move the aircraft to a safe altitude. You do not have to know what is going on. You do need to know how to stabilize the aircraft and place it in a safe position so you then have the time to figure out what is going on.


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Old 4th May 2019, 16:14
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Originally Posted by 737 Driver View Post
Which is precisely why, when presented with an undesired aircraft state, unknown or ambiguous malfunction, or a loss of situational awareness, the flying pilot must be ready and able to Turn off the magic, Set the Pitch, Set the Power, Trim the aircraft, Monitor the performance, and Move the aircraft to a safe altitude. You do not have to know what is going on. You do need to know how to stabilize the aircraft and place it in a safe position so you then have the time to figure out what is going on.
The first step in your mantra is "turn off the magic". What Boeing did by implementing MCAS severely undermines that first step, because they added an additional bit of "magic", that can't be turned off using the old procedures (A/P off, A/T off, FD off). Instead, turning off this bit of "magic" requires disabling manual electric trim as well, with the cutout switches.

I think it wouldn't hurt if Boeing would implement some way to disable automatic trim independently from manual electric trim. Something that can disable both STS and MCAS without forcing you to use the trim wheels for the rest of the flight.

Since making significant changes to the cockpit like adding switches is probably out of the question, maybe there should be a way to completely disable automatic trim, using existing switches. For example using the existing cutout switches. Placing them in the cutout position, waiting a few seconds, then switching them back to normal could be used as a way to disable automatic trim, but leave manual electric trim functional. That would require just a software change.

Then your mantra would work just fine, if you include this additional sub-step of "Auto-Trim Off" as part of "turn off the magic".
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Old 4th May 2019, 16:23
  #4880 (permalink)  
 
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Originally Posted by 737 Driver View Post


Which is precisely why, when presented with an undesired aircraft state, unknown or ambiguous malfunction, or a loss of situational awareness, the flying pilot must be ready and able to Turn off the magic, Set the Pitch, Set the Power, Trim the aircraft, Monitor the performance, and Move the aircraft to a safe altitude. You do not have to know what is going on. You do need to know how to stabilize the aircraft and place it in a safe position so you then have the time to figure out what is going on.



with all respect, Sir
turn off magic... that was possible on previous 737, before max... lets do not talk about AB.
MAX is different from any other 737, you cannot turn off magic... in case of trim stab... you turn off power! Not magic, Sir, turn off power, and manual wheel is smaller than in the 400s...hence higher force required to crank.
still with all due respect Sir, how hard is to move the trim manually on a MAX? (If you ever tried)
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