One last time: Please look at the ET traces from 05:40:00 (first MCAS) to 05:40:45.
This shows MCAS trimming down, an inadequate pilot retrim followed by another MCAS trim 5 seconds later, this second MCAS trim was interrupted after 6 seconds by pilot trim.
This pilot trim continues until trim cutout. Had they waited 10 more seconds while continuing to apply trim the AC would likely be in trim.
Each of these trim inputs clearly show on the pitch trim trace.

All of the above is exactly as described by original MCAS 'disclosure'.

Not sure where the '3 sec up' in your post comes from, the second pilot trim in above is 8 or 9 seconds (hard to read exactly from graph).

They did re-enable electric trim at end, likely a desperate measure, unfortunately they did not provide sustained trim inputs but did re-trigger MCAS one last time.
The trim position trace at 05:43:15 show a slight upward bump after the 2 'blip' showing the electric trim working against the aero loads.
The trim inputs would not show on the trace if still cutout due to cutout switch wiring.

"One last time" the FDR trace does not track thumb switch trim inputs. Therefore, it cannot be said with certainty what the pilots were doing. The assumption is that Boeing advice is correct but it is not absolutely certain. Unless you can authoritatively show that MCAS has no authority during thumb switch input in all circumstances then you are speculating.

Ok I will bite:
Unless you can authoritatively show the FDR trace does not track thumb switch trim inputs a reasonable interpretation of the traces is that it does. I have not seen anything that shows otherwise.

As to whether the switches tracked the pilots thumb and or intentions is possibly an open question, especially the blips at the end.

Don't know about "all circumstances" but the trace at 05:40:27 shows the manual trim stopping MCAS before the full 9 or seconds it would have run.

The schematic that was posted also shows manual electric trim overriding automatic,the 'trim motor' is shown as a block so can't 'prove' this.

In any case not clear where this is going, in ET case MCAS is clearly disabled by pilot trim (for 5 seconds) and cutout, had they succeeded with manual trim we would not be having this discussion.

No need for elaborate undisclosed actions, the stated behavior explains what is seen.
Occam's razor might be constructively considered here.

Still concentrating on the Human Factor - the miserable consuming confusion while under stress.

Recently I said.
However, Lord Farringdon put it far better, and in commoner's language.

Hopefully by now the ET captain may well have linked the duff AoA with an airspeed error and stick-shake, but not the failure of the AP to stay locked on for more than thirty seconds. He was probably processing that while the wheel spun for 9 seconds.

I recall leaving the classrooms after Type conversions with a reasonable knowledge of system interactions . . . at best. Usually, the light-bulb would come on after 300 to 500 hours and a lot of work. How one system affected another was the most difficult part of any type conversion for me, and in the modern world, I'd imagine the MAX is an order of magnitude more involved. I have to concede 737 Driver's 'Fly and then press on with the drills', rather than analyse too deeply is vital. It's simply too complex these days.

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Minor correction, after a couple of false starts the autopilot was engaged for more than 30 seconds, just long enough to provide a false sense of "not that bad"?
Then it all hit the fan on short order with AP disconnect followed by MCAS.

Threat and Error Management
 

Part 3

Continuing the Threat and Error Management discussion..... If you are joining midway through, I highly recommend that you go back to the beginning (Part 1) starting with the post with the TEM graphic.

The TEM model posits that there will always be threats, that there will always be errors, but that by intelligently designing and employing sufficient barriers, threats can be identified and mitigated, and errors can be trapped before they lead to an undesired aircraft state, incident, or accident.

Threats and errors were covered in the previous post, and a list of potential barriers were identified. I left off with what I thought were two germane questions:

Why did the existing barriers fail?

What happens when a barrier actually becomes a threat?

​​​​​Once again, traditional aviation barriers that apply to flight deck operations include policies and procedures (SOP's), checklists, crew resource management (CRM), knowledge and aircraft handling skills, as well as external resources (ATC, maintenance, etc). CRM procedures would include briefings, communication, active monitoring, deviation callouts, assignment and execution of pilot flying/non-flying pilot (PF/NFP) duties. Knowledge and aircraft handling skills would determined by the particular training and experience of each pilot.

Which of these barriers failed? (easier question) Why did they fail? (harder question)

Unfortunately, not enough is known of the specific Ethiopian SOP's, crew discussions prior to takeoff, or specific training and experience to definitively address some of these questions. However, we can still make some (hopefully) useful observations. The data that has been released to date suggests that the ET302 Captain did not fully process the nature of the malfunction (perception error). Having not perceived the true nature of the malfunction, he proceeded to apply inappropriate procedures (attempting to engage A/P, retracting the flaps before the AOA/UAS malfunction was resolved). The repeated attempts to inappropriately engage the autopilot and subsequent aircraft handling (particularly the lack of aggressive trimming against the MCAS input) suggest a lack of comfort with hand-flying. At this point, it is impossible to say how much of the Captains actions were driven by a particular lack of knowledge or skill, or rather, the inability to draw upon that knowledge or skill under pressure. However, I think it is a reasonable observation that, to the degree that any barriers resided within the mind of the Captain (perception, SOP's, knowledge, aircraft skills), these barriers were ineffective. In short, the Captain could not trap his own errors. When errors are not properly trapped, they can convert to new threats. Or to put it another way, what should have been barriers actually became threats.

How did these barriers become threats? There are signs that the Captain was experiencing cognitive overload. Contributing issues could include fatigue, distraction, pressure to meet schedule, inadequate training, and/or perception that he was effectively single pilot (more on that in a moment). Whatever the reason, the TEM model does suggest an appropriate response when barriers become threats.

Before that discussion, I need to touch on one other aspect of this accident. Based upon some of the previous feedback, I suspect some of you are not going to like this part, but I feel this is a necessary exercise. There was another potentially useful barrier on the flight deck that day - the First Officer. This is an interesting case in that I have already identified a low-time FO and the possible existence of a steep authority gradient on the flight deck as potential threats. So was the FO a threat or a barrier? Or a little of both?

One piece of information we do not have is whether any steps were taken to mitigate the FO as threat. How well did the Captain know the FO and how did he perceive the FO's competency? Did he enquire as to his recent experience or if he had any particular questions? How thoroughly did the Captain brief his FO? Did the Captain perceive that there was a potentially hazardous authority gradient, and if so, did he attempt to mitigate it with clear guidance to the FO that he was expected to speak up as necessary?

Now let's discuss the FO as a potential barrier. In a two-pilot crew operation, each pilot is expected to back up the other and help identify and mitigate threats as well as trap errors. They are also expected to work together to resolve any non-normal procedure.

One of the remarkable aspects of the CVR discussions that have been released so far are not so much what was said, but what was not. There is very little discussion of the ongoing malfunction or the state of the aircraft. There is no discussion of airspeeds or altitudes. No one calls for any checklists, normal or otherwise. When the Captain tries to engage the autopilot with an active stick shaker (three times!) the First Officer does not question this action. By the time the aircraft reaches 1000' (and before MCAS ever showed up on the scene), the signs of unreliable airspeed were present. The Captain was absorbed in flying the aircraft and apparently greatly distracted. What was the First Officer doing? A fully qualified and proficient FO should have been monitoring both the aircraft and the Captain. He should have identified the UAS situation, but did not do so. If he had identified the UAS, he should have called for the appropriate NNC himself if the Captain did not do so. When the Captain called for the flaps to be retracted while they had an active stick shaker and before any non-normal procedure had been called for, the First Officer simply did as requested and did not question whether it was an appropriate action. As the airspeed increased toward VMO, the First Officer said nothing. When the Captain was obviously applying an excessive of back pressure on the control column without sufficient trimming, the First Officer did not prompt the Captain to trim or ask if the Captain needed help inputing trim. By not trapping any of the Captain's errors, those errors now converted to new threats. The First Officer failed to be an effective barrier.

Some have pointed out, seemingly to the First Officer's credit, that it was he who finally identified the runaway stab trim problem (we should note for the record that the First Officer only made this observation the second time MCAS began it's 9-second, 37 spin journey to oblivion). But rather than this being a positive result, it was actually the final link in a long chain of errors that doomed this aircraft. Yes, that's right, the First Officer introduced his own deadly error into the chain.

From the transcript:
.



When a non-normal checklist is needed, the procedure is for the first pilot seeing the problem to call out the problem (In this case "We have runaway stab trim") and then for the other pilot to confirm ("Yes, I agree. We have a runaway stab."). This is a quote from my airline's FCOM: "Prior to performing procedures, both pilots should communicate and verify the problem."

"Stab trim cutout" is not a problem. It is a command (maybe suggestion?). "Runaway Stab Trim" is a problem. When the First Officer said "stab trim cut-out", the (likely overloaded) Captain pounced on the suggestion, one of the pilots cutout the trim, and they were finally and fatally screwed with a stabilizer in an untenable position and no effective way to move it.

The next step in a non-normal situation is for one of the pilots (at some airlines it is the Captain, at some airlines it is the Pilot Flying) to call for the appropriate NNC procedure. Again from the FCOM: "Identifying the correct procedure is critical to properly managing the non-normal situation."

There is a bit of divergence here depending on whether the airline uses a Quick Reference Card (QRC) or the "Memory Item" method. My airline uses a QRC, but basically the goal is to work through the steps in a methodical fashion. Grabbing controls and switches without careful thought can lead to all sorts of misery. Think here of those accidents that resulted from crews shutting down the wrong engine during an engine fire/failure in flight response. From the FCOM: "Non-normal checklists use starts when the aircraft flight path and configuration are correctly established......Usually, time is available to assess the situation before corrective action is started. All actions must then be coordinated under the Captain's supervision and done in a deliberate, systematic manner. Flight path control must never be compromised." In other words, fly the aircraft first, and don't rush through the procedure.

Okay, I know some might find the preceding paragraphs tedious, but they are important to understand this final fatal error.

The Runaway Stabilizer checklist has been previously posted, so I won't duplicate it here except to enumerate two particular steps. Step 2 of this NNC states: "Autopilot (if engaged) .... Disengaged. Do not re-engage the autopilot. Control aircraft pitch attitude manually with control column and main electric trim as needed." It is not until Step 5 of this checklist that we get this: "If the runaway continues after the autopilot is disengaged: STAB TRIM CUTOUT switches (both)..... CUTOUT." It should be added that it is really not necessary that all the words be said correctly as long as all the actions are performed correctly.

By methodically following the published procedure (rather than responding reflexively to the First Officer calling out "Stab Trim Cutout!"), the Captain would have been prompted to trim the aircraft with the Main Electric trim - the very thing he most needed to do after MCAS kicked in. Only after the aircraft was returned to neutral trim was it appropriate to use the stab trim cutout switches, not before.

The First Officer should have been a barrier. Instead he was a threat.

The Captain should also have been a barrier to his own errors and the errors of his First Officer. Being unable to trap either set of errors, those errors became threats.

Too many threats, too many errors, not enough effective barriers.

So we are now left with (a variation of) my final question:

What should one do when a barrier actually becomes a threat?

737 Driver
I see the wisdom in much of your post, one thing to keep in mind though is that we have glaringly incomplete CVR facts, not a transcript just some snips possibly selected to shore up a particular point of view.
This makes it impossible to know all of what was discussed etc during (and before) the flight or the full extent of interactions.

As I have said before something was going on while the trim was in cutout mode, we just have not been told what.

I agree it is an incomplete picture (which I did acknowledge), but there are some broad enough outlines from which we can draw some conclusions. If anything comes out that substantially alters our current understanding, then I'll be happy to make a correction.

As far as what was going on while the the trim switches were in the cutout position, are you referring to the gradual movement from 2.3 to 2.1 units? It apparently occurred over two and half minutes. I'm interested in seeing what the board's thoughts are on that as well, but I should point out that in the context of the overall trim movement, it is a very small and slow creep.

737 Driver
"the possible existence of a steep authority gradient on the flight deck as potential threats."

Cue to possible existence of a steep authority gradient on a flight deck by employing metrics used to evaluate and judge Korean Air and third world cockpits.

Cactus fifteen fifty minus one, UsAir flight 1539 revisited.

15:29:45.4 hot-1 ok lets go put the flaps out, put the flaps out. ( this is not a proper command)
15:29:48 hot-2 flaps out? (Skiles not sure about what his captain wants him to do, Sully silent.)
15:30:01 hot-2 got flaps out.

15:30:06 cam-2 hundred and seventy knots.
15:30:09 cam-2 got no power on either one? try the other one.
15:30:16 hot-2 hundred and fifty knots.
15:30:17 hot-2 got flaps two, you want more? (Skiles somehow sensed that Sully wants to stay airborne so he gave him best glide flaps.)

Mitigated Speech and Plane Crashes (Outliers, p 195)

1- Command: “Turn thirty degrees right.” That’s the most direct and explicit way of making a point imaginable. It’s zero mitigation.
2- Crew Obligation Statement: “I think we need to deviate right about now.”Notice the use of “we” and the fact that hte request is now much less specific. It’s a little softer.
3- Crew Suggestion: “Let’s go around the weather.” Implicit in that statement is “we’re in this together.”
4- Query: “Which direction would you like to deviate?” That’s even softer than a crew suggestion, because the speaker is conceding that he’s not in charge.
5- Preference: “I think it would be wise to turn left or right.”
6- Hint: “That return at twenty-five miles looks mean.” This is the most mitigated statement of all.

In that scale above ” you want more?” is a “querry” in line 4 and a “hint” ( you should have more ) in line 6. Both indicative of mitigating speech is employed. By mitigating speech being employed we deduce that there is a strong authority gradient in the cockpit.

The repetitive hyperbole in your posts masks any real content for discussion that may exist.

The above quoted strawman is not an accurate allegory for the actual events which occur when the MCAS system is activated. It does not demand "zero tolerance for deviation", nor does it require "using an exact mechanism" to diagnose what is essentially a runaway stabilizer trim event.

Mitigation does require correct diagnosis and reaction. The actions of the ET 302 crew were sadly deficient in both regards. Discussion of their response and examination of aircrew training and competency overall is of more interest to me than your insistent claims of nefarious negligence by Boeing and the FAA.

Any MAX pilots here?
 

Are there any contributors here who are 737 pilots who transitioned to the MAX?

May I ask please,
If you did, did you have any SIM, classroom, or Line training on the MAX and it's differences, or was it purely on-line modules, thus was your first flight on a ''pax on board'' flight?

Were you made fully aware of the adverse pitch up changes, and CG issues of the new MAX due to the design enforced forward location of the new larger engines (which can now cause lift) at low weights/high power applications resulting in a (unrecoverable?) high AOA? (which we now are aware, necessitated the MCAS software patch)

Were you (before the 2 fatal and 1 nearly accidents) fully informed/trained on the new MCAS systems and it's functionality, implications, and what to do if it went rogue?

Thanks.

Rog,

No one knew about MCAS until the AD a couple of weeks after the Lion Air accident. Have a look at the thread. The crew that saved the situation described the problem as the STS running the wrong way, possibly a huge clue as to how the human mind interpreted what was happening (rather than a trim runaway).

All operators used CBT rather than real training.

OK thanks -
so what you are saying would also confirm that no pilots (putting aside MCAS as you say) were ever made aware of the adverse pitch up effect of the new MAX due to the location of the larger engines (which can now cause lift) at low weights/high power applications resulting in a (unrecoverable?) high AOA?

Its buried in the thread, but if you want an up to date reference, the 60 Minutes documentary (video and text) provides some interviews. For example Dennis Tajer (APA union). See: https://www.9news.com.au/national/60...6-a0c47ddfe293

Rog - you don't have that quite right. It's high AoA that results in different stick forces. In normal operations the pilot would not ever create an AoA that would allow him to explore the new stick forces. Boeing logic was that if the pilot inadvertently found himself in such a high AoA condition, then all would feel normal because MCAS would trigger. Boeing just failed to explore what would happen if the single input to MCAS failed causing it to repeatedly trigger when not wanted.

Apart from this lack of 'fail safe', add the failure to inform pilots of MCAS having been fitted, to install an 'MCAS on' warning and to signal the need for appropriate training including how to disable MCAS if required. Did Boeing also not fail to advise the FAA of a change in the scale or parameters of MCAS*?

*Ref Schmerik above : "There's the change of the rate of trim applied made late in the testing stages (from 0.6 units to 2.5 units per time period?)"

Which rather vindicates Boeing's position on this; they reacted exactly as Boeing intended by identifying it as an STS runaway (which most assuredly is a runaway trim event) and dealt with it by using the correct pre-existing technique.

And as such, why is it really so necessary to inform pilots of this system? There is no specific control over it, just the generic runaway trim procedure. Surely telling people about systems they have no specific influence over is merely muddying the waters? If it presents itself as failure event X which is dealt with by checklist Y does anyone need to know that it could be system A or A.1 at fault, when both are addressed by the same checklist, show effectively the same symptoms and actually are components of the same system?

That, I am sure, was Boeing's rationale and though I'm not 100% comfortable with it I'm certainly not condemning it in the absolute and fundamental way some others are.

I very much doubt that could be the case. Single input failures would be top of the list to explore if the system only had one input. I think suggesting otherwise is being far too simplistic in automatically assuming gross incompetence where there really is no evidence of it. I read somewhere they spent 205 hours test-flying MCAS. What do you suppose they were looking at in all that time? That single-input failures hadn't occurred to anyone? No one at all? That is simply preposterous.

Boeing's big 'mistake' was to underestimate the public and to some extent the industry's interpretation of two failures due almost exclusively to bad handling and incorrect procedures that they could hardly have anticipated. At least, Boeing thought they could hardly have been anticipated at the time, and I doubt (m)any of us would have thought otherwise either before these accidents had we known about the system. Their mistake was to underestimate the amount and volume of criticism that would unexpectedly come their way because crews, maintenance and at least one airline screwed up in spades and the world retrospectively devined faults therefrom in Boeing that no one had thought were faults before and in a vindictive and vitriolic way unprecedented in the history of aviation.
Caught out by the 'told you so' all-seeing retrospective 'wisdom' of the internet more than anyting else.

I'm not saying they're whiter than white, just some light-ish shade grey a very long way from the midnight black some others are portraying.

Where are the howls of outrage over this 'cynical corporate cover-up' then, if adding automatic systems and not telling is so iniquitous?
Or could it be this falls into the same category as MCAS before the accidents? It's not hurt anyone so no one is outraged? (not suggesting this is an exact parallel but appears a similar concept). I expect Airbus' view on this was very similar to Boeing's on MCAS though; it is a sub-system of something else and failures in it can be identified and grouped under a common, pre-existing drill and as you have no control over it's operation what is the point of confusing people with knowledge of something they can't affect independently.