Ethiopian Airlines Crash; Another 737 Max

[TCABM]

United has the AOA DISAGREE warning as well.

Didn’t know that about UA.

SWA, AA, and DL use the HUD for CAT II/III approaches and all have the AOA displays (at least in the HUD). UAL uses autoland for CAT II/III and does not have the AOA display.

It’s not about the HUD, it’s about the PFD.

The AOA DISAGREE checklist in the QRH tells you that the left and right AOA vanes disagree and that you may have airspeed and altimeter errors along with their associated "IAS DISAGREE" and "ALT DISAGREE" alerts. There are no pilot actions in the checklist. I don't see how that would be helpful to pilots who are facing a stabilizer runaway. It would be one more thing distracting them from the real threat.

Considering at the time of Lion Air, no one knew about MCAS, and even after, not all was known, any additional information to help diagnose what was occurring may have been helpful but, like computing MCAS saves, its an unknown.

I’m also not convinced it’s the AOA vane either, but potentially the data from the sensor may be getting corrupted or mis-processed somewhere along the way. Or there’s literally wires getting crossed somewhere along the way.

If there had been any additional MCAS activations recorded by FOQA, or reported via ASAP, we'd know about them by now.

I would hope so, but I can’t speak to how information from foreign airlines would make its way to the US reporting systems.

All of this is to say we’re probably closer to agreement than it appears; I happen to be of the opinion Boeing probably did not fully understand the failure mode(s) and/or probably did a poor job of understanding the human reaction to those failure modes.

 

[TCABM]

Sully was USAir, not UA. Cactus.

Yes it’s a been a long night. The analogy still stands.

 

[Silvaire]

Like I said earlier the media is over-hyping the whole “optional” AOA Disagree warning aspect. They already have airspeed and altitude disagreements and one of the stick shakers activating. Having another AOA specific warning is just redundant, it’s not going to help them determine which side is wrong.

 

[TCABM]

Like I said earlier the media is over-hyping the whole “optional” AOA Disagree warning aspect.

The media maybe, but peel the onion some.

We had an issue on the E-3 that came to light about 25 years after platform acceptance.

The jet was approved for up to 40 aircrew/pax onboard. We had a fire/smoke/fumes event in 2006 or 2007 where we ended up freezing O2 bottle refiller ports with ~26 aircrew only onboard (all breathing off masks, except the 3 guys in the lobe on bottles and one guy up top on a bottle to pass empties/refills back and forth.

When the refiller port froze, it froze open, with LOX spitting out of the port. First time it happened, and the idea of LOX being fed in a F/S/F event bothered the USAF, so Boeing got a call. Now, using those ports and bottles occurred on nearly every single training sortie, but the it took the right sequence of events for bad things to happen.

Sure enough the problem was replicable and could occur quite often given the larger O2 bottles the E-3 (with Boeing’s blessing) was retrofitted with. New guidance was issued to limit the the jet to 29 aircrew/0 pax l until a solution could be developed, which I don’t know ever came about since I left for staff shortly thereafter.

Critical thinking requires going beyond the first order of effect and applies to engineers as much as it does to aircrew. And I’d be really surprised if the failure modes and recovery procedures were actually flight tested.


ETA: Boeing could have easily had the AOA disagree Alert display as MCAS TU/Disable Stab Trim Cutout. That would have been helpful.

 

[3393RP]

In all this hoohaw, I find it quite distasteful a criminal investigation into this matter has been initiated by the DOJ. I believe that action could upset the openness and impartiality of future NTSB investigations.

Is the US now going to operate like the Italians and French when an airliner crashes?

 

[LongRoadBob]

The procedure does not include turning the electric trim back on.

It also doesn't include retracting the flaps below 500'.

Looking now like you may have it. It’s being reported that a bird strike or foreign object may have damaged the AOA sensor, and that yes, they didn’t follow the whole procedure.

I think that as others mentioned, it has to be a memory flow response. I mean how much time was there between the problem beginning and the crash? I'm guessing not enough to fight the plane, and lookup checklist procedures.

But they did do "the procedure" but not the next one, that is what is being said now? They also undid some of the procedure, but if I understand it might or might not have been apparent to them (i.e. power up on something also re-enabled the system?)

And though it may be apparent to many here, the thing about the flaps. I don't know enough about how airliners handle, how the flaps work there.

Just from my SEP understanding, flaps on different types of airplanes affect attitude differently. On some when you deploy they tend to nose up, on others nose down.

On that type of airplane what is the attitude tendancy from retracting or deploying?

Also what was the range of the change in flaps, flaps retraction? Was it from full to none, or some degrees to some other lesser degree?

I don't know what they were trying to accomplish with that, from my small experience and training flaps in the first degrees of deployment give more lift than drag, but as you extend further start to add more drag than lift. And again, the nose (attitude) change.

I'm not trying to say it wasn't pilot error, or that it was. Or that it wasn't a combination of bad design and pilot error, etc. I don't know. What I was and have been reacting about is the folks that assume because it is a third world country (countries) that it was pilot error, that they didn't "know" the procedure, or attempt it.

So when news came out that they apparently had done the procedure (yes...maybe not all, I don't know) it was against that backdrop.

I'm done. I know I don't know. Still will wait for the final report.

 

[Sluggo63]

Living over here in Europe, this has been blowing up the news all morning and afternoon while most of you folks are still sleeping over there. The preliminary accident report is out, but not yet been made public. From what everyone is reporting, the pilots tried to use the recommended procedure and it didn’t work. Some agencies are using the phrase “the pilots ‘repeatedly’ used the Boeing recommended procedure.”

It’ll be interesting once the report is released. But, at initial glance, it looks like these guys did cut out the stabilizer (at least once). I could only speculate what happened after that.

https://www.nytimes.com/2019/04/04/...tion=click&module=Top Stories&pgtype=Homepage

 

[Tj1376]

Living over here in Europe, this has been blowing up the news all morning and afternoon while most of you folks are still sleeping over there. The preliminary accident report is out, but not yet been made public. From what everyone is reporting, the pilots tried to use the recommended procedure and it didn’t work. Some agencies are using the phrase “the pilots ‘repeatedly’ used the Boeing recommended procedure.”

It’ll be interesting once the report is released. But, at initial glance, it looks like these guys did cut out the stabilizer (at least once). I could only speculate what happened after that.

https://www.nytimes.com/2019/04/04/...tion=click&module=Top Stories&pgtype=Homepage

We shouldn’t have to speculate about what they did. The FDR tells us that. The CVR may give us some insight into what they were thinking and the why behind what they did.

It’s increasingly suspect that we haven’t received that data. And the FAA response to the initial report makes me think they are just as suspect about the words spoken at that press conference.

TJ


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[PPC1052]

Here's one explanation:
"MCAS normalises a stick force gradient that does not fully meet the applicable certification standard § 25.173 Static longitudinal stability, sub paras a through d. It is not a stall prevention mechanism. Stall warning requirements are specified in § 25.207 Stall warning and for handling in § 25.203 Stall characteristics. Compliance with the latter is exhibited in demonstration compliant with § 25.201 Stall demonstration. The lifting body effect of the engines is a non linear effect, at a modest relative inflow angle, they will develop lift, at high angles that lift increment will not occur, and inertial forces will dominate the aircrafts behaviour, weight is still forward of the Cp, the plane will pitch down at the break #.

The non linear stick force gradient issue is not permitted to be so significant that the failure of the augmentation system precludes flight within the operational envelope, and specifically up to the stall. § 25.672 Stability augmentation and automatic and power-operated systems.

In simple terms, the control force in part of the operating envelope, outside of normal flight conditions experienced by the RPT pilot, but within the full flight envelope did not meet the standard that was set half a century ago, in a time where the automation and instrumentation would have made it unacceptable to fly for a period of time an aircraft that had say the same control forces as a Lancair 360, and which are still more applicable to IFR operation than a Pitts or an Extra. The Lancair, Pitts and Extra can easily be flown by instruments, it is just undesirable for long term comfort, and therefore the system safety. To remove the issue, Bill Boeing added the MCAS, which is a variant of the STS that has been there for years on the SLUF, dealing with a similar issue in a small part of the envelope around retracting flaps and initial acceleration, e.g., 3rd segment."

I'm sorry. You took my post seriously. I was merely pointing out the dichotomy between the term "intermittent" (as in application of trim), and consistent (as in column forces). I'll try to do better next time. But the information provided is helpful. Thank you.

 

[Kenny Phillips]

... ETA: Boeing could have easily had the AOA disagree Alert display as MCAS TU/Disable Stab Trim Cutout. That would have been helpful.

Maybe. There are cockpit recordings of a continuous "Stall ... Stall ... Stall ..." being announced, whilst the pilots were pulling back on the yokes.

 

[Piperonca]

Here's a comment from pprune today, sums it up.

"There were actually two failures on the MAX: The faulty AOA sensor data which triggered a whole range of spurious warnings, put the pilots in a high workload situation, which on its own was hazardous. Then MCAS comes along, and administers the coup-de-grace while the pilots are busy trying to make sense of the aircraft and their checklists."

 

[Larry in TN]

It’s not about the HUD, it’s about the PFD.

Two, disagreeing, AoA indications would not have been helpful. That, in conjunction with stick-shaker (stall warning) which had been going off since liftoff, would have pointed them toward a stall (the nose drops during a stall, too) instead of the real problem; the runaway trim. Frankly, with everything that was going on, it's unlikely they would have even noticed what the AoA displays were displaying.

any additional information to help diagnose what was occurring may have been helpful

I disagree. Information overload is not helpful. It is a distraction that hides the real issues.

Their challenge was the continue to fly the airplane through all the distractions. This would mean continuing to use the primary trim to keep the airplane close to an in-trim condition while holding the pitch attitude in an appropriate place (anywhere in the 5° - 15° ANU range would work). Then, identifying the persistent, uncommanded nose-down trim inputs as a runaway stabilizer and accomplishing that procedure.

I would hope so, but I can’t speak to how information from foreign airlines would make its way to the US reporting systems.

If foreign airlines had data which would make Boeing look bad do you think they would be withholding it?

I think that as others mentioned, it has to be a memory flow response. I mean how much time was there between the problem beginning and the crash? I'm guessing not enough to fight the plane, and lookup checklist procedures.

A runaway stabilizer procedure is standard on every airplane with powered trim from GA airplanes to every transport jet. It is trained for in every initial training course on these airplanes. The switches are right there in the middle of the center console below the thrust levers. It should not have been a mystery to them. If they were flying the airplane first they would have been keeping the stabilizer close to an in-trim condition through the use of the primary electric trim and there wouldn't have been any immediate time pressure to complete the procedure.

The data suggests that they were not re-trimming the airplane after each MCAS activation which allowed the trim to move progressively toward the full nose-down position (the position in which the jackscrew was found). When they finally did cutout the stab trim the aircraft was already trimmed too far nose-down and they didn't have time to trim it back up manually.

 

[chemgeek]

Here is what bothers me: if the AOA indicators disagree, why is MCAS even allowed to initiate corrective maneuvers? Why isn't an AOA disagreement a mandatory software reporting element in the preflight aircraft control checks? This is engineering 101: you shouldn't be putting a single point failure mode in a critical system. Making this kind of basic safety system check "optional" is quite frankly ludicrous.

 

[Tantalum]

Have you ever stared at a clock for 40 seconds.. it's a long enough time, and these should be memory items, not complicated look through manuals and checklist items. I grant that the Boeing system is flawed, but I do not grant that it should be killing people. Someone mentioned the runaway acceleration before in Audi, Toyota, etc., that came down to a pedal spacing and floor mat issue. Funny how those same people did not simply think to put the car in neutral

 

[Tantalum]

Here is what bothers me: if the AOA indicators disagree, why is MCAS even allowed to initiate corrective maneuvers? Why isn't an AOA disagreement a mandatory software reporting element in the preflight aircraft control checks? This is engineering 101: you shouldn't be putting a single point failure mode in a critical system. Making this kind of basic safety system check "optional" is quite frankly ludicrous.

This is where I take fault with Boeing as well, but only to the degree that "it's a stupid design" - not to the degree that it is a lethal design. The pilots are not helpless passengers along for the ride to press a few buttons.. they're the captains and in charge of the ships they command. The very fact that some crews crashed while others didn't (with the same issue) shows that this is a survivable event

 

[Piperonca]

Preliminary report: http://www.ecaa.gov.et/documents/20...AVJ).pdf/4c65422d-5e4f-4689-9c58-d7af1ee17f3e

 

[kayoh190]

Why isn't an AOA disagreement a mandatory software reporting element in the preflight aircraft control checks? This is engineering 101: you shouldn't be putting a single point failure mode in a critical system. Making this kind of basic safety system check "optional" is quite frankly ludicrous.

I completely agree that it shouldn't have been a single point failure mode - I was making p!$$ed off posts about that shortly after the first crash. But one reason you can't test for agreement on the ground is that it's not uncommon for the vanes to be pushed around by winds, jetblast, or whatever else while at the gate or taxiing around - since the winds (usually) aren't hitting both sides of the nose in exactly the same manner, the position of the two vanes commonly won't match until you get up to some speed on the takeoff roll.

 

[dmspilot]

Preliminary report: http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+,(ET-AVJ).pdf/4c65422d-5e4f-4689-9c58-d7af1ee17f3e

Well so far it's raising more questions than answering.

They positioned the stab trim to cutout mode, and confirmed the procedure worked. The report doesn't say anything about the pilots reactivating it, yet this happened with no explanation as to how:

At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds.
​

 

[Silvaire]

...Why isn't an AOA disagreement a mandatory software reporting element in the preflight aircraft control checks? ...

The AOA sensors are just simple vanes, until the aircraft reaches a specific speed their data is meaningless and is ignored by the computers. The apparent critical flaw of the MCAS is that it only uses one AOA and has no capability of knowing if there is a split in data. That in itself is probably one of the "fixes" they are going to implement.

 

[Tj1376]

Well so far it's raising more questions than answering.

The report doesn't say anything about the pilots reactivating the electric trim. Yet this happened with no explanation as to how:

At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds.
​

I think you actually wrote it in your reply. I believe a manual electric trim input can only be made if the electric trim switch is operational.

The way I read it is that the copilot could not manually trim up. They were over speeding the aircraft so I think he’d have to fight that wheel to push against all that air pressure. Which sounds like it was not possible. So they turned the switches back on and an ANU input was received and moved the stabilizer. But then MCAS. And this is where I think it gets really bad for Boeing. MCAS in one interval moved that stabilizer from 2.3 to 1.0 in five seconds. At their speed I bet that was catastrophic...

I haven’t read the whole report. Just the transcript of events. Will read some more and see if that changes my thoughts.

Curious also how the big iron guys read it.

TJ


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[dmspilot]

I think you actually wrote it in your reply. I believe a manual electric trim input can only be made if the electric trim switch is operational.

The way I read it is that the copilot could not manually trim up. They were over speeding the aircraft so I think he’d have to fight that wheel to push against all that air pressure. Which sounds like it was not possible. So they turned the switches back on and an ANU input was received and moved the stabilizer. But then MCAS. And this is where I think it gets really bad for Boeing. MCAS in one interval moved that stabilizer from 2.3 to 1.0 in five seconds. At their speed I bet that was catastrophic...

There's nothing about it anywhere in the report. As you pointed out, one could deduce that one of the pilots must have taken the stab trim back out of cutout mode, but it seems like the report is trying to hide it, or they honestly don't know how it happened.

 

[Chip Sylverne]

First observation is the transcript does NOT make them sound like a couple of poorly trained bumbling idiots in the cockpit. Second observation is I didn't read a call out to re-engage cutouts, so that last AND is troubling. I doubt very much one of the two pilots would have taken that action silently. Finally, if disengaging power to the trim, and trimming manually is supposed to be the failsafe, that ripcord didn't work with the airplane in that part of the envelope.

 

[Tj1376]

There's nothing about it anywhere in the report. As you pointed out, one could deduce that one of the pilots must have taken the stab trim back out of cutout mode, but it seems like the report is trying to hide it. Must be why the WSJ source that reported as such wanted to remain anonymous.

I don’t think there is anything about it in the report as the position of the switches may not be monitored by the DFDR. The statement they make is accurate. Mcas commanded AND at 5:40:42 but the stabilizer did not move. That tells me the cutout switches were cutout (the report also makes that same distinction.)

At 5:43:11 two ANU inputs were received and moved stabilizer from 2.1-2.3 units ANU. That isn’t going to happen if the cutout switches are engaged.

Then five seconds later mcas moved that stabilizer significantly nose down. Again, we know that won’t happen if the cutout switches are disengaged.

So either:
Pilots turned them back on (no fault here- they couldn’t get the nose up.)
Cutout switches were defective and did not work (which contradicts 05:40:41 where mcas commanded AND and stabilizer did not move.)

I’m not into conspiracy’s. I don’t see anything glaringly wrong here. The pilots couldn’t get the nose up so they **probably** tried electric trim (which did work!) but then MCAS moved the stabilizer way too much and they were way too fast.

Let’s not disagree too much about it too much here and muddy this thread with just our two opinions- let’s see what the other pilots have to say.

TJ


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[Tommar98]

This is where I take fault with Boeing as well, but only to the degree that "it's a stupid design" - not to the degree that it is a lethal design. The pilots are not helpless passengers along for the ride to press a few buttons.. they're the captains and in charge of the ships they command. The very fact that some crews crashed while others didn't (with the same issue) shows that this is a survivable event

I have a question for software people. Why wouldn’t the MCAS system look at all the available flight info such as speed, altitude, VSI, etc and piece together something is wrong? Why can’t the system determine its getting bad info from one system that doesn’t have info that’s matching what other systems are providing? That’s what we ask pilots to do - I don’t see why a computer processing alot of info very fast can’t piece this puzzle together. Especially when the aircraft is speeding toward the ground. I am not a software engineer or aircraft designer - just seems odd that a safety feature of sophisticated software can’t resolve what we want the pilots to resolve in 6 mins.


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[dmspilot]

I’m not into conspiracy’s. I don’t see anything glaringly wrong here. The pilots couldn’t get the nose up so they **probably** tried electric trim (which did work!) but then MCAS moved the stabilizer way too much and they were way too fast.

Let’s not disagree too much about it too much here and muddy this thread with just our two opinions- let’s see what the other pilots have to say.

I'm not trying to come up with a conspiracy theory. I'm just pointing out the paradox that the report discusses the stab trim was cutoff successfully but does not talk about it being un-cut-off. The electric trim being used again after being previously deactivated should at least have been a bullet point in "Initial Findings".

 

[Silvaire]

I don’t think there is anything about it in the report as the position of the switches may not be monitored by the DFDR...

Of course they are that recorder monitors 1,790 parameters and it's apparent that even with all of that data in front of us and several weeks to think about it we still don't know what happened. We should definitely lighten our criticism of the crew.

 

[Matthew]

The info on the FO having low hours in in there, too:

361 total
207: 737
58: Max 8

and 207 in previous 90 days.

--

The first part of the report shows the pilot side AOA jumping from about 15 deg (matching the other AOA) to 75 deg in about a second, at about 50' AGL.

The questions we had about flaps being retracted early: they were retracted starting at 1000'. AP engaged first, flaps retracted to 0, AP disengaged. Now it's in the MCAS control window, and 5 seconds later the first automatic nose down trim started.

 

[AKiss20]

I don’t think there is anything about it in the report as the position of the switches may not be monitored by the DFDR. The statement they make is accurate. Mcas commanded AND at 5:40:42 but the stabilizer did not move. That tells me the cutout switches were cutout (the report also makes that same distinction.)

At 5:43:11 two ANU inputs were received and moved stabilizer from 2.1-2.3 units ANU. That isn’t going to happen if the cutout switches are engaged.

Then five seconds later mcas moved that stabilizer significantly nose down. Again, we know that won’t happen if the cutout switches are disengaged.

So either:
Pilots turned them back on (no fault here- they couldn’t get the nose up.)
Cutout switches were defective and did not work (which contradicts 05:40:41 where mcas commanded AND and stabilizer did not move.)

I’m not into conspiracy’s. I don’t see anything glaringly wrong here. The pilots couldn’t get the nose up so they **probably** tried electric trim (which did work!) but then MCAS moved the stabilizer way too much and they were way too fast.

Let’s not disagree too much about it too much here and muddy this thread with just our two opinions- let’s see what the other pilots have to say.

TJ


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The report says that the FO explicitly tried manual trim and reported “it wasn’t working”.

At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.

If manual trim isn’t working and you can’t pitch up due to trim imbalance, re-engaging electric trim seems like a last ditch attempt to get it to work.

 

[kayoh190]

The manual trim situation bothers me - I'm wondering if our simulators don't take into account aerodynamic loads when providing resistance to the wheel, and we certainly don't see stab runaway in the sim under conditions like what these pilots experienced. In a nose low, high airspeed event with a large amount of nose down trim and back pressure on the yoke - does anyone (including Boeing) know what kind of forces are needed to manually trim the stab nose up?

One other thing - the manual trim wheels on the 737 aren't like those on a GA airplane where you can make significant trim changes with a flip of the wrist or a couple of fingers. It requires a number of revolutions of the wheel, and while there's a handle that can extend from the side to help the pilots crank away - with higher than expected forces required to move the wheel and very limited time to recover - if you let the stab get too far away from you before getting to the cutout switches, perhaps it's too late.

Speculation of course, but this is the stuff running through my head at the moment.

 

[sourdough44]

Just an aside, yes I have taken back a fully loaded 737 with just the manual trim wheel, flaps 15 landing per the book. It’s not that much of a biggie, electric stab trim inop. No I didn’t have the stick shaker going off the whole time.

What does one do after getting a warning light off the night Cat shot? You do absolutely nothing except continue a wings-level climb, deal with it later.

O.K., maybe I can only handle one thing at a time. Just some idle thoughts.

 

[kayoh190]

O.K., maybe I can only handle one thing at a time. Just some idle thoughts.

In the last couple of weeks I've experimented with using the manual trim wheel instead of electric, and while it works, I'm also always in a relatively neutral trim state the entire time. I'm curious to know how it'd feel under their trim and airspeed circumstances, which of course I can't duplicate while on the job.

 

[Pilawt]

The info on the FO having low hours in in there, too:

361 total
207: 737
58: Max 8

and 207 in previous 90 days.

Leaving 96 hours in anything other than a 737. Wow.

 

[Silvaire]

The 737 trim wheels have offset handles specifically for the purpose of allowing both pilots in conjunction to have the leverage needed to overcome aerodynamic forces so obviously this is known to be a factor. But try doing it while both pilots are also pulling heartily back on the yokes and less than a minute to impact and all because some form of rudimentary artificial intelligence thought it knew better than the humans what to do. If it were a pilotless aircraft of the future there would have been no fight, no resistance, just straight into the ground like a lawn dart.

 

[Silvaire]

Leaving 96 hours in anything other than a 737. Wow.

Why do people dwell on this when it was not, as far as the evidence shows so far, a factor?

 

[Matthew]

The report says that the FO explicitly tried manual trim and reported “it wasn’t working”.

At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.

If manual trim isn’t working and you can’t pitch up due to trim imbalance, re-engaging electric trim seems like a last ditch attempt to get it to work.

Looking at the tracings (a little hard on my monitor), there are a series of manual (electric) nose up trim commands mixed in with automatic nose down trim commands. Then there's a single automatic nose down command that notes say does not change the pitch trim, possibly this is where the cutoff switches were thrown and the command was sent but nothing moved. There is no more indication of manual electric trim until some time later. They may have been trying to turn the wheel manually during this time, but the trace doesn't show any change in pitch trim. Finally there are a couple of electric trim nose up commands that seem to have no effect, followed by an automatic nose down that does have an effect (this might be were the assumption is being made that the system was re-enabled.)

I don't know the systems - would turning off the stab trim also disable electric trim from the control wheels? It seems like the crew was trying, but no signals were being sent.

 

[TCABM]

...But then MCAS. ...

I’m curious if anyone outside of Boeing actually knows whether or not Stab Trim Cutout actually stops MCAS from providing further inputs.

Put differently, when Stab Trim Control switches are set to Cutout, does that actually remove all power from all motors used to adjust pitch trim, preventing MCAS inputs from being implemented at the motors.

 

[sourdough44]

I’m curious if anyone outside of Boeing actually knows whether or not Stab Trim Cutout actually stops MCAS from providing further inputs.

Put differently, when Stab Trim Control switches are set to Cutout, does that actually remove all power from all motors used to adjust pitch trim, preventing MCAS inputs from being implemented at the motors.

No electric stab trim with switches in cutout. One has to use the manual wheel.

 

[Chip Sylverne]

In the last couple of weeks I've experimented with using the manual trim wheel instead of electric, and while it works, I'm also always in a relatively neutral trim state the entire time. I'm curious to know how it'd feel under their trim and airspeed circumstances, which of course I can't duplicate while on the job.

As part of your training, do you experience what the MAX control forces are with MCAS deactivated at high angles of attack? Do you know what yhe airplane would feel like if you could switch it off in that portion of the envelope?Just curious with all this cavalier "just switch it off" talk if the airplane is actually controllable without it.

 

[dmspilot]

I’m curious if anyone outside of Boeing actually knows whether or not Stab Trim Cutout actually stops MCAS from providing further inputs.

Put differently, when Stab Trim Control switches are set to Cutout, does that actually remove all power from all motors used to adjust pitch trim, preventing MCAS inputs from being implemented at the motors.

The report explains that.

HISTORY OF FLIGHT
...
AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position​

and

1.6.2 AIRCRAFT FLIGHT CONTROL SYSTEM DESCRIPTION
...
Stabilizer Trim
The STAB TRIM PRI cutout switch and the STAB TRIM B/U cutout switch are located on the control stand. If either switch is positioned to CUTOUT, both the autopilot and main electric trim inputs are disconnected from the stabilizer trim motor.​

 

[dmspilot]

As part of your training, do you experience what the MAX control forces are with MCAS deactivated at high angles of attack? Do you know what yhe airplane would feel like if you could switch it off in that portion of the envelope?Just curious with all this cavalier "just switch it off" talk if the airplane is actually controllable without it.

There aren't any Max simulators owned by U.S. airlines, and the pilots got trained with iPads, so I think that answer is no.