The flight previous to the LA crash also experienced the MCAS malfunction. You don't hear about that one because the crew used the electric trim switches to return trim to normal, then turned off the stab trim system with the cutoff switches.
Then, they continued the flight and landed normally.
The next flight on the same airplane is the one that crashed. The crew restored normal trim with the electric trim switches 25 times, but never shut off the trim system.
The EA crew also restored normal trim with the trim switches, but then turned off the trim when the stabilizer was too far nose down. This is contrary to the instructions in the Boeing Emergency Airworthiness Directive distributed to all MAX pilots.
This does not absolve Boeing's role in not doing a proper failure analysis of the MCAS system.
But contrary to what Frontline said "the pilots did everything right" it was recoverable if the instructions for runaway trim were followed.
The Ethiopian Airlines pilots followed the EAD to the letter.
First, they attempted to adjust trim using electric stabilizer trim, and then upon realizing that the they were experiencing an uncommanded nose down stabilizer trim, they followed the runaway stabilizer procedure - namely, stab trim cutout and trim wheel grasp and hold. Afterwards, they attempted to adjust the stabilizer manually.
There is a note in the EAD that electric stabilizer trim can be used to neutralize the stabilizers before doing a stab trim cutout, but crucially Boeing did not instruct pilots to make sure to neutralize trim first using electric trim before doing the stab trim cutout.
ERROR: Literally the first paragraph of the EAD is about controlling airspeed. [Edit: This is not correct]
They hit 700(!!) MPH. They literally commanded full take off power to accelerate the plane into the ground. You can add power if your pitch is high to arrest a sink rate (ie, during landing), but if you are pitched down, you pull power.
There is also a 300 second limit on T/O power - I'd be interested if they exceeded that as well.
The maintenance on this plane was terrible.
This was not a situation where folks involved "did everything right".
For those not familiar, approx 3 minutes after they did a stab trim cutout they put stab trim back to normal. That's never been in any guidance for EAD or runaway.
The 4th activation of MCAS moved trim down (to 1 unit, should have probably been at 4.3 - 5.x or so). That probably doomed them.
"Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually."
The entire EAD must be read, not the first paragraph. Including the digressions (your phrase). It's only two pages.
I am not a pilot. But I am an aerospace engineer who worked on critical flight detail designs. You've likely flown on my work. My father was a pilot for the AF for 20 years. You don't get to be an old pilot if you don't pay attention 100% to the instructions and training. Flying isn't like driving a car. Humans are not natural flyers. You rarely get a second chance if you make a mistake flying.
Maybe 90% of flight training is dealing with emergencies. If you're not dedicated to doing it right, and doing it 100%, every time, you've got no business being a pilot with hundreds of lives depending on you.
P.S. I've gone flying with pilot friends many times. I watch them do the preflight. If they're not 100% perfect with it, I'm getting off.
One advantage in flying - you are pretty much told EXACTLY how to do many things.
This is what makes me think flying will be automatable. There are a lot of checklists already written for almost everything. Ie, electrical power up, preflights, (CDU preflight?) before taxi before takeoff etc.
Runaway trim was a memory item (!). ie, so important you have to have it memorized.
What's interesting is that because of a jammed actuator motor in an earlier US situation (way back) they have this language about a "maximum two person effort will not break the cables"
This is because you have to basically break out of a clutch and friction condition if a motor seized which aside from the MCAS crashes could require pretty large efforts.
There is evidence of somewhat routine stab trim issues, at least 1x per year mistrim stuff, and more often inop etc. Before these crashes I don't think it was considered even a very serious concern because pilots would handle it in ordinary course of things.
> One advantage in flying - you are pretty much told EXACTLY how to do many things.
Experience shows that will get you safely out of the vast majority of emergency conditions. The ones that are left require understanding and a brain, which is why we still have human pilots.
Runaway stab trim is so serious a condition that the cutoff switches are within easy reach right there on the console. It doesn't really matter how many safeguards there are against runaway trim, the pilot needs to be able to just turn the thing off. It's also deliberate that the electric trim switches override everything but the cutoff switches.
Pure speculation on my part, but I suspect that Boeing thought that it was so easy to just turn off a misbehaving trim system, that the pilots would just do that.
It's sort of like one day I was working away on my desktop, and smoke started boiling out of the case. My first reaction was to pull the plug out. Fortunately, that stopped the fire. If it hadn't, my second reaction would have been to throw the box outside.
My lawnmower, power tools, etc., are all designed so that chopping the power to them is as easy as possible. Even race cars have a large switch mounted on the exterior to shut off all power.
> Boeing did not instruct pilots to make sure to neutralize trim first using electric trim before doing the stab trim cutout.
Yes, they did:
"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."
> That's not an instruction - it's a digression. The wording there is "can be used".
Why do you think Boeing wrote an EMERGENCY AIRWORTHINESS DIRECTIVE and the FAA mandated it be sent to all MAX pilots?
If you're a pilot, it is YOUR JOB to read, understand, and remember every EMERGENCY AIRWORTHINESS DIRECTIVE. Not to parse words. If you want to parse words, get a job as a lawyer, not a pilot.
The "can be used" is there to explain how to overcome aerodynamic forces that make using the manual trim wheel difficult.
Please don’t flag replies like this; thankfully I was able to vouch for Walt.
For some background, Walt and I are routinely brigaded with downvotes on 737 MAX threads. What he and I have in common, compared to those who engage in such behaviors, is that unlike those we typically are replying to, we both have extensive backgrounds in the aviation field, especially on the programming side.
Back on topic, the takeaway that Walt is making and that seems to be missed continually in these threads, is that Lion Air did not lose their plane due to the MAX’s MCAS implementation. Rather, the pilots engaged with the plane in a manner precisely opposite to what procedure calls for. Despite all of the poor calls made by Boeing here, if LA’s pilots had simply reacted as the previous flight’s pilots had, the plane would have made it.
A clarification - my computing experience at Boeing was writing Fortran programs to solve design problems, not aviation software.
However, at Boeing I spent 3 years working on the stabilizer trim gearbox on the 757. The 757 system is a newer design than the 737, in that it uses a dual drive system connected via a differential gear system rather than having the manual wheels in the cockpit. Nevertheless, the difference is in detail, not concept. Both systems have cutoff switches within easy reach of the pilot, for a damn good reason - to stop uncontrolled stabilizer trim action. While the 757 did not have MCAS, it did have a computer autopilot that could move the stabilizer.
I did some searching online of the MAX trim system, and indeed the electric trim switches override MCAS commands. In all three incidents the pilots did override it and return the trim to normal.
In the first incident, after a couple times, the crew trimmed it to normal and then cutoff the stab trim. Continued the flight and landed without further incident.
In the second, the pilots brought it back to normal 25 times before the final plunge. For whatever reason, they never switched off the trim system.
I haven't got a solid reference to the EA one, but it appears they restored trim twice before the final plunge. They then turned off the trim system in the plunge. They could not turn the manual trim wheels due to the aerodynamic forces. So they turned the trim back on, the MCAS came on again making things worse. Why they did not counter again with the electric trim I do not know. Why they did not turn off the trim when it was in the normal position I do not know. Those are excellent questions for the NTSB to answer.
But what they didn't do was follow the directions in the EAD.
The first LA crew was not aware of the existence of MCAS, nor did they have the benefit of the Emergency Airworthiness Directive. But they worked the problem and solved it and landed safely.
Not to mention I think they ran the plane at full takeoff power during the recovery attempt - I can't even imagine what they were doing in terms of speed monitoring (in a nose down you normally reduce power, no go to full takeoff!).
The pre-MAX 737 has a cut-off switch that switches of the automatic trim system, without also switching of the electric trim (there's another one that switches off the electric trim). The 737 MAX also has two switches, but they both switch off the automatic trim (including MCAS) and the electric trim.
So you can't switch off MCAS without also switching off electric trim, leaving only manual trim. But in situations like the Ethiopian flight, you need inhuman strength to control the manual trim (as Mentour Pilot demonstrates in this video: https://www.youtube.com/watch?v=aoNOVlxJmow). You need electric trim to have any chance to fight MCAS, but you can't enable electric trim without also enabling MCAS. Must be horrific to be in such a situation.
The EA crew followed that memory item. It didn't work. (Had they reduced the throttle it probably would have helped, which is why the need to limit speed during runaway trim events has been added to the updated memory item now)
Then, they continued the flight and landed normally.
The next flight on the same airplane is the one that crashed. The crew restored normal trim with the electric trim switches 25 times, but never shut off the trim system.
The EA crew also restored normal trim with the trim switches, but then turned off the trim when the stabilizer was too far nose down. This is contrary to the instructions in the Boeing Emergency Airworthiness Directive distributed to all MAX pilots.
This does not absolve Boeing's role in not doing a proper failure analysis of the MCAS system.
But contrary to what Frontline said "the pilots did everything right" it was recoverable if the instructions for runaway trim were followed.