Originally Posted by sgrd0q (Post 2801032)

I should start by saying that I am not bashing the crew in either accident;

Originally Posted by sgrd0q (Post 2801032)

I blame Boeing 100%.

Originally Posted by JohnBurke (Post 2801062)

You really should.



Boeing didn't fly the airplane into the ground.

Do you blame Smith and Wesson for a liquor store robbery?

Originally Posted by JohnBurke (Post 2801062)

Boeing didn't fly the airplane into the ground.

Do you blame Smith and Wesson for a liquor store robbery?

Originally Posted by ItnStln (Post 2801131)

That’s actually a good analogy.

Originally Posted by Fdxlag2 (Post 2801178)

.. a single unannounced malfunctioning probe

Originally Posted by Adlerdriver (Post 2801225)

:confused: If it was "unannounced" why did both pilots verbalize "left alpha vane" at the same time during the event?

Originally Posted by sgrd0q (Post 2801032)

Looking at the Ethiopian preliminary accident report and the one from the Lion Air accident, I am starting to think there is generally lack of training and understanding of how to trim in an extremely out of trim condition.
A "general lack of training and understanding" where? Here in the US? :confused: I and my peers at the 3 airlines I've worked at along with those in the USAF seemed to have a pretty good handle on trimming. :rolleyes:

I should start by saying that I am not bashing the crew in either accident; I blame Boeing 100%. But I think everyone may be somewhat deficient in this area. Quite the broad brush you paint with - Everyone is deficient in what?.... Trimming again?


Generally, trimming in the usual scenario is an easy balancing act. There are three key points, the action is quick, it is done automatically/subconsciously and the feedback is instant. This is similar to driving a car and keeping it in your lane – you observe the car getting closer to one side, you make a quick small adjustment automatically/subconsciously and you get an instant feedback when you see the car move to the other side. This is repeated many times per minute. It is a balancing act. Another analogy is riding a bicycle, particularly at slow speed – you make small inputs, subconsciously (it is much harder to explain to your kid how to do it, vs just doing it) and the feedback is instant. It is the same with walking - also a balancing act. So the action of trimming is very straight forward and everyone does it reasonably well, just like driving, or riding a bike, or walking, whichever analogy you prefer.

The situation is different in an extremely out of trim state. Trimming is now not a small, instant, automatic adjustment, and even worse - the feedback is grossly distorted. What I mean by this is this – imagine you are pulling hard at the control column, say 100 pounds. Nobody, no matter how strong can sustain this for any significant period of time. You get tired. Your muscles want to give out. So you trim in the usual way, for a short burst, the back pressure is so much that you get very small relief comparatively, but you may not even perceive it. The feedback is distorted. In fact as you get tired, you may even feel like you are pulling harder, even though you got a small relief. So the feedback loop is broken. Your brain is wired to not keep on if there is no positive feedback, and you stop and move on to the next thing. This paragraph and the one above are based on the assumption that a pilot attempting to trim has no actual understanding of the physics involves, the relationship between airspeed and trim setting and what he is actually doing by moving the trim switch (or the manual trim wheel for that matter). If a pilot has to pull 100 lbs of force to move the yoke back in attempt to raise the nose, he knows his aircraft is grossly out of trim for the current speed. If he doesn't then he shouldn't be in the aircraft in the first place. 100 lbs of pull on the control column is going to tell any competent pilot that he's going to have to trim like crazy to get it back into a normal range. He's not going to give a couple of clicks of trim, have the control forces go to 99 lbs, shrug his shoulders and give up because the problem wasn't instantly corrected. This whole "feedback loop" discussion is nonsense.
If a pilot in a grossly out of trim aircraft tries one small attempt to trim, gets no immediate relief and then gives up, it's because he has no idea what he's doing - not because of some distorted "feedback loop".

The failure to trim properly is astounding in both accidents.

Really? What if both crews never bothered to hand fly the aircraft. What if the entirety of their actual hand flying experience in the jet is takeoff roll, rotation, climb to 500' in t/o configuration, followed by autopilot on - then on final, clicking it off at 300' fully configured, fully trimmed and landing.

With the Ethiopian accident, you have the captain (pilot flying) doing very little to trim after the MCAS kicks in and while they still have the electric trim. His feedback is distorted and he likely assumes his trim is not working so he asks the first officer to help trim. The first officer does a great job pulling up with him, but is also not nearly aggressive enough with the trim. All the while they both recognize the out of trim condition. Then, of course, per the procedure they cut off the electric trim which is great because that kills MCAS, but not so great because they are now grossly out of trim, not controlling the speed (unfortunately), and ultimately finding that the manual trim wheel is not working in that configuration. At some point after that one of them (presumably the CA) turns on the electric trim. I don’t think this was a bad idea as others have speculated. At this point they are exhausted holding the back pressure, the manual trim wheel is not working presumably due to the speed and they have no other options. Throwing the procedure out of the window is the right call as there is no more procedure to follow. You have to do what you have to do to recover.

But they didn't "do what they have to do". They turned a malfunctioning system back on and they did nothing with it. Justifying their actions with logic they weren't using doesn't validate their choices. It also makes no sense to approve of a decision matrix that starts at a point that no competent 737 crew should have allowed their aircraft to reach in the first place. So I would assume you turn the electric trim on and you absolutely lay on the thumb switch. It has been shown that not only you can interrupt MCAS but you can actually override it – as the Lion Air CA did repeatedly on that flight. The most disappointing thing with the Ethiopian accident is that they turned on the electric trim and did very little trimming. There is one blip on the graph where they tried, it changed little and they let go, then another blip, then nothing. They assumed it was not working. They gave up. Then MCAS kicks in and finishes the job. This is the most disappointing aspect.

With the Lion Air accident, the captain actually does a great job trimming nose up repeatedly, for many cycles of MCAS activation and for many minutes. Then he presumably gives control to the first officer, who is not nearly as aggressive and crashes.

This is astounding, 3 out of 4 pilots, 75%, failed to use the trim aggressively enough in a severely out of trim state. As for the Lion Air captain (again pilot flying) – to his credit he catches the first MCAS activation early enough, so he never gets in truly severe out of trim state – so the feedback loop is not as distorted and he is successful in trimming up. This then repeats many times and he gets into a groove with this, into rhythm, going back and forth and staying on top of it. We don’t know how he would have fared if he started with an extreme out of trim condition to begin with.

One may think this is all training, and a student pilot should be able to trim, but it goes beyond that. Everybody trims and does a good job under normal circumstances when the feedback loop is there. Once you go into an extreme out of trim situation and the feed back loop is distorted then this is an entirely different skill – you will need to trim, your only feedback will be the trim wheel spinning, and you will have to be persistent and not give up. :rolleyes: Back to the feedback loop and pilots who apparently have no idea what trim is actually doing and are unable to differentiate between needing more or less depending on airspeed and control forces.

Not many were put in that situation in real flying before MCAS, save for a few test pilots who do that sort of thing on purpose.

I believe there is a training opportunity here – not how to trim under normal conditions, and not on any specific procedure either, but rather training to be persistent and aggressive with the trim even when it feels like it is not working. Hold the damn button for five, ten, fifteen seconds - whatever it takes. Again, if this concept is new to any pilot, may I suggest that pilot find another line of work.

Originally Posted by Adlerdriver (Post 2801321)

100 lbs of pull on the control column is going to tell any competent pilot that he's going to have to trim like crazy to get it back into a normal range. He's not going to give a couple of clicks of trim, have the control forces go to 99 lbs, shrug his shoulders and give up because the problem wasn't instantly corrected. This whole "feedback loop" discussion is nonsense.

Originally Posted by sgrd0q (Post 2801338)

.. all I know is that they sure knew how to trim and did it all the time under normal circumstances.

Originally Posted by ItnStln (Post 2801131)

That’s actually a good analogy.

Originally Posted by sgrd0q (Post 2801338)

Incredibly, the Ethiopian crew did just that. I refer you to page 26 of the preliminary report. Look at the graph at time 5:43:15 - two short clicks. That is it. Then the MCAS dials in nose down trim and it is over:

Originally Posted by sgrd0q (Post 2801338)

I am not going to label them as competent or incompetent - all I know is that they sure knew how to trim and did it all the time under normal circumstances. Then when the forces were too great and the feed back loop non-existent they all of a sudden could not do it.

Originally Posted by sgrd0q (Post 2801338)

Why on earth would you want someone to click on their thumb switches with you unless you believe the trim on your side is not working? And why does he think it is not working? Surely because the feed back loop is distorted - the correction is small, he does not feel it and he gives up. This is my interpretation, you are welcome to disagree.

Originally Posted by trip (Post 2801404)

That's a stupid analogy. A better analogy-The S&W misfired because of a poorly designed firing pin. While attempting to clear the mis-fire the S&W discharged killing the user.

Originally Posted by JohnBurke (Post 2801483)

You understand neither the report, nor the aircraft, nor the system.

The control wheel nose-up trim attempt at 5:43:11 occurred as pilot-action. This is very significant, because at 5:40:35, nearly three minutes prior, the crew had already used the stab trim cutoff switches. Once the stab trim cutoff switches have been moved to the cutoff position, stab trim may not e re-engaged.

The recording of pilot electric trim input at 5:43:11, with subsequent increase from 2.1 to 2.3 units, is evidence that the crew re-engaged the pitch trim motors.

The pitch trim then moved nose down from 2.3 units to 1.0 unit. THIS WOULD NOT HAVE OCCURRED IF THE CREW HAD NOT RE-ESTABLISHED PITCH TRIM MOTOR CAPABILITY BY RESTORING THE POSITION OF THE STAB TRIM SWITCHES.

Read that again in case you didn't get it.

Once the stab trim motors have been cut off, the stab trim motor cutoff switches must NOT be restored. The crew restored them, thus enabling the trim to run away again.

At the same time, they continued to make the trim force problem WORSE by accelerating.

Originally Posted by JohnBurke (Post 2801483)

The captain made several requests of the F/O. Trim with me. Pitch with me. Pitch with me.

The crew didn't trim in the wrong direction. The issue of a "feedback loop" is irrelevant. The controls were heavy nose down, due to an out of trim condition. They made an attempt to restore it, with minor success, but the let the trim run nose down again. They attempted to retrim, cut it off, and would have been required to maintain back pressure based on an out of trim condition, but it was manageable and flyable at that point. Only two things could have made it worse: re-engage the stab trim motors, and increase airspeed.

Originally Posted by sgrd0q (Post 2801494)

I am assuming they kept accelerating and probably realized they could not maintain level flight in that configuration due to the control column pressure, and they could not move the trim wheel manually, again presumably because of the aerodynamic forces involved at that speed.

Originally Posted by sgrd0q (Post 2801494)

If we put aside whether they should or should not deviate from a procedure, whether they should or should not exceed Vmo, and everything else they may or may not have done right - at some point they found themselves with electric stab trim restored.

Originally Posted by sgrd0q (Post 2801494)

Right or wrong, they did it. We can analyze and debate what they did right and wrong prior to that point, but lets put that aside, as it detracts from my main point - which is that after the electric trim was restored, at that point one would assume they would aggressively trim with the thumb switches (and in the process override MCAS), instead they barely did anything - two clicks at around 5:43:11 and 5:43:15. That in my mind is incredible. Then the MCAS commands nose down trim at what looks like 5:43:20 for about six seconds and shortly after they lose control.

Originally Posted by sgrd0q (Post 2801494)

By the way, when they cut off the stab trim motors, they were so out of trim that it is not a given, based on what we know, that the plane was flyable, no matter the speed. You can hold the pressure for so long until your muscles give out.

Originally Posted by Adlerdriver (Post 2801524)

But the speed does matter. It’s the main reason the aircraft became uncontrollable. Had they stayed in the flight envelope, any trim setting, even an extreme one would have still been flyable. It wasn’t until that trim setting was combined with a speed well beyond limits that the aircraft was un-flyable. So saying “no matter the speed” as if the trim position alone doomed the aircraft makes absolutely no sense.

Originally Posted by sgrd0q (Post 2801572)

Do they have the muscle strength to see this through?

Originally Posted by sgrd0q (Post 2801572)

I should add that we are going off on a tangent here. They didn't even try to slow down, so this is all highly hypothetical. My initial point was about trimming or failure to trim in extreme conditions.

Originally Posted by Xjrstreetcar (Post 2801850)

You don't think that the likelihood that this failure on any other type variant would have ended up differently is relevant? Certainly relevant to establishing a new type or not...

Originally Posted by Xjrstreetcar (Post 2801868)

I must have missed that the groundings and coming modifications go beyond the Max..

Originally Posted by Xjrstreetcar (Post 2801892)

Was that dude some sort of lobbyist? Hard to determine given that his post history is hidden..Didn't seem to handle cognitive dissonance well..

Originally Posted by ShyGuy (Post 2802620)

John Burke, while blaming 4 dead men is easy, you can’t overlook or give a pass to Boeing’s critical errors:

Originally Posted by ShyGuy (Post 2802620)

Boeing will settle the lawsuits, just watch.

Originally Posted by ShyGuy (Post 2802620)

John Burke, while blaming 4 dead men is easy, you can’t overlook or give a pass to Boeing’s critical errors:

1. After Boeing itself said that failure of MCAS itself is a “hazard” level threat, the system by definition should never have been hooked up to only one sensor for information. By definition, a hazard level failure mode requires more than one source for information. It’s a safety requirement. Boeing failed.

2. Putting in paperwork for the feds that MCAS only travels 0.6 deg per activation, whereas reality was it travels 2.5 degrees in one go. And max travel is a little over 5 degrees on the stab trim. Boeing made the system act 4x more than what they told the feds. Boeing failure.

3. No limit on MCAS activation per occurrence of high alpha sensed. Every time the system reset with trim switches, it can run again. Unlimited cycles. 2.5 each time, 2 cycles if left unchecked will get a fully trimmed nose down. This is also a Boeing failure, when their intention was just to ease the nose down in case of high alpha due to engines being positioned higher and further forward.

4. No MCAS info passed to airline customers, nor crew. That’s a horrible failure on Boeing’s end.

For decades the saying was if it ain’t Boeing, I ain’t going. That has largely to do with the fact that Airbus has law protections, and “the computer” can get the final say and/or override the pilot. Boeing, the pilot has the final authority.


MCAS changed all that. And Boeing rolled it out horribly.

You say they should have recognized it as stab trim runaway and done the memory item for cutoff switches. Easy to say now, keep in mind they were faced first with a bad AOA sensor, a stick shaker that was on throughout, and false instrument readings. And MCAS runs the trim temporarily and stops, so it doesn’t look like a full on runaway.

Imagine if Boeing had told airlines and pilots about MCAS. If they had the proper system knowledge, maybe one pilot would have said, maybe it’s that MCAS thing, let’s get the flaps out of 0, it’ll stop. Flaps 1. And everyone lives.


The foreign regularity authorities and airlines were absolutely right to ground the MAX. The FAA let Boeing self-certify too much itself, and Boeing broke basic safety rules (see item 1-4 above).

Boeing will settle the lawsuits, just watch.

Originally Posted by ShyGuy (Post 2802620)

You say they should have recognized it as stab trim runaway and done the memory item for cutoff switches. Easy to say now, keep in mind they were faced first with a bad AOA sensor, a stick shaker that was on throughout, and false instrument readings. And MCAS runs the trim temporarily and stops, so it doesn’t look like a full on runaway.

Originally Posted by JohnBurke (Post 2801483)

You understand neither the report, nor the aircraft, nor the system.

The control wheel nose-up trim attempt at 5:43:11 occurred as pilot-action. This is very significant, because at 5:40:35, nearly three minutes prior, the crew had already used the stab trim cutoff switches. Once the stab trim cutoff switches have been moved to the cutoff position, stab trim may not e re-engaged.

The recording of pilot electric trim input at 5:43:11, with subsequent increase from 2.1 to 2.3 units, is evidence that the crew re-engaged the pitch trim motors.

The pitch trim then moved nose down from 2.3 units to 1.0 unit. THIS WOULD NOT HAVE OCCURRED IF THE CREW HAD NOT RE-ESTABLISHED PITCH TRIM MOTOR CAPABILITY BY RESTORING THE POSITION OF THE STAB TRIM SWITCHES.

Read that again in case you didn't get it.

Once the stab trim motors have been cut off, the stab trim motor cutoff switches must NOT be restored. The crew restored them, thus enabling the trim to run away again.

At the same time, they continued to make the trim force problem WORSE by accelerating.



You don't know that.

Clearly they had one mission with unwanted trim motion: cutoff the stab trim motors and leave them cutoff. That singular action would have prevented this mishap, had they been left in the cutoff position, and had the crew not continued to accelerate.

As stated previously, it's possible to make a salvageable situation unsalvagable, and that's exactly what the crew did.



It is your interpretation. It's wrong.

The captain made several requests of the F/O. Trim with me. Pitch with me. Pitch with me.

The crew didn't trim in the wrong direction. The issue of a "feedback loop" is irrelevant. The controls were heavy nose down, due to an out of trim condition. They made an attempt to restore it, with minor success, but the let the trim run nose down again. They attempted to retrim, cut it off, and would have been required to maintain back pressure based on an out of trim condition, but it was manageable and flyable at that point. Only two things could have made it worse: re-engage the stab trim motors, and increase airspeed.

The crew did both. And it killed them.



Not at all.

The 737 Max didn't misfire, nor was it poorly designed. First and foremost, a sensor failure occurred: the crew recognized the sensor failure, and already had notification in their flight manual of the potential complications of an AoA failure; this notification had been in their flight manuals for several months.

The procedure for unwanted stab trim, regardless of the cause, is the same. It's fully applicable here. It's not new. It's been in play for decades. It's spelled out in the report, in case you don't know it. The single most important element of that procedure is a memory item: stab trim cutout switches CUTOUT.

Once those switches are placed in cutout, they are not to be restored. The crew restored stab trim operation, knowing that stab trim motion was nose down, and that it was uncommanded.

This was not a faulty design or aircraft: this was a faulty pilot action, and a fatal one. Accelerating beyond Vmo in the aircraft sealed it. No chance of recovery, and they rode it into the ground with the overspeed clackers going off the entire time.

No, if a man robs a liquor store with a S&W handgun and shoots the clerk, it doesn't matter if he fumbled the safety at the time, and it doesn't really matter if the pistol has a mechanical problem and discharges without his finger on the trigger: it's his action, robbing that store, that killed the clerk, and it won't help him a bit to try to pawn it off on the pistol.

A pilot in command has the ultimate responsibility for the safe outcome of the flight. He knows that malfunctions can occur in the aircraft; it's quite literally all we train to do, is handle them. Ultimately, however, our first job is to fly the aircraft, and we have procedures to do this; the procedure was violated in this case, and it was that violation that allowed the trim to decrease further nose down, and on top of that, the crew allowed the aircraft to continue to accelerate, thus increasing the nose-down force as the flight diverged farther and farther from it's trimmed speed. Additionally, leaving power in and flying it beyond it's maximum operating speed, entirely out of the operating envelope, eventually prevented any possibility of recovery.

If you want to pick nits about a pistol analogy, the pilots were robbing the liquor store, and held the pistol on the clerk. They engaged the safety (stab trim cutoff switches), and at that stage, there was no chance of shooting the clerk...not until they disengaged the safety (restored the stab trim motors), and set the ball rolling. Everything they did thereafter only sealed the fate, and that's pilot action, not a manufacturer failure.