Without more information on what the background and training of those pilots, and why the one failed, I'm afraid it's just an anecdote.
In both crashes, the trim came on repeatedly and the crews repeatedly brought it back to normal with the electric trim switches. 25 times in the case of the LA crash. They obviously knew that the trim was the problem, because they took this corrective action. The trim running is obvious by the large black&white spinning wheels in the cockpit, and the deliberately loud clacking sound the running trim makes.
All they had to do was then turn it off.
> But they didn't. And innocents paid for it.
That's right, and that's the tragedy.
As to why they didn't, who knows. The stab trim cutoff switch is right there in a priority position on the console, because it's a damned important switch. Dealing with runaway trim is supposed to be a memory item, i.e. memorized.
It does suggest a training problem.
Nobody is blaming the engineers for this. But it is, by design, a bad system, that can by attrition defeat human decisions.
http://airsoc.com/articles/view/id/5d5143c7c4263ce96fd616b6/...
Differen source.
https://aviationweek.com/air-transport/software-fix-will-add...
The civillian trained test pilot lost it. The two military pilots did not.
"In one scenario, the bits chosen first told the computer that MCAS was engaged when it wasn’t. This had the effect of disabling the cut-off switches inside the pilot-control column, which normally stop any uncommanded movement of the horizontal tail if the pilot pulls in the opposite direction."
The cutoff switches cannot be disabled on the airplane.
"They flew the same fault scenario again, this time deliberately allowing the fault to run for some time before responding. This time, one of the three pilots didn’t manage to recover and lost the aircraft."
That's kinda vague.
There it is! Knew it was in SeattleTimes somewhere!
And lookout for the part about disabling cutoff switches, I think Dominic might have written that better, because I think he's talking about a safety function that was removed specifically for the MAX where hauling back hard on the yoke would stop trim commands in progress on NG airframes? MCAS required that that functionality not be ported forward to the MAX.
This isn't disabling those cutouts though. Those are literally, like you said, a hard switch.
>According to a second FAA source, it was the AEG pilot, representing a typical U.S. airline captain, who failed to recover the jet.
There's the bit about the civilian test pilot.
It's a hard switch for good reason. I hate "soft" switches that supposedly disable microphones. Phooey on that.
BTW, on my hotrod I installed a hard switch to shut off the fuel pump, as well as an oil pressure switch that would shut it off. I have a g-switch to cut it off, too, but haven't gotten around to installing it.
So the procedure for runaway trim (turn off electric trim, use hand wheels) doesn't work. You have to instead use electric trim first to get back into normal trim, then turn off the electric trim, and never turn it back on for that flight.
I feel like this isn't talked about enough. I had no idea how bad it can actually get: https://youtu.be/aoNOVlxJmow?t=806
There is some discussion amongst pilots at https://www.pprune.org/tech-log/619326-boeing-advice-aerodyn... which further explains how difficult it can be to manually reduce load on the stabilizer and manually trim the nose up.
With the gear ratios we're talking with by hand actuation, I would not want to have to be one of those pilots.
Aviation rules are written in blood. Training is being updated and fixed. But regardless, MCAS itself is controversial and fallible - it’s crucially important that Boeing make it better.
It was mentioned repeatedly Walter; if not in the articles, then in the comments. The fact remains that afterward, when regulators put more pilots (two military and one civilian trained) pilots into single-event upset simulations, 1 of the three failed to recover the plane in time.
If you acknowledge the training was faulty, then just let it be. Trim runaway presenting continuously vs. intermittently may not seem that important from a clean room engineer's perspective, but when viewed by a pilot through the lens of instruments, blaring alarms, and whatever else is going on in the cockpit, my engineer's optimism favors not relying on the human being perfect, or the defect only happening at a non-terminal part of the flight regime.
It sucks that it played out the way it did. Maybe if someone would have spent as much time on MCAS and the pilot training as you did the 757 auto-trim, it wouldn't have been an issue.
But they didn't. And innocents paid for it.