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by cmurf
2447 days ago
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There's no evidence MCAS upset looks exactly like runaway trim in every case, most cases, some cases, or these specific cases. This is a supposition made only by Boeing, and repeated by others. What has since been demonstrated is it's possible for MCAS upset to result in a mistrim significant enough the pilots can't recover in time if they're at a low enough altitude. So I reject the categorical claim they could have recovered with the flip of a switch. Further to that point, the preliminary report on ET302 shows they did turn stabilizer trim switches to cutoff, and yet they couldn't move trim manually, likely due to mistrim forces. The logical reason why they turned stabilizer trim back on is it was the only way to get electric motor assisted trim to try and get out of the mistrim. But MCAS immediately triggered again resulting in greater than 20 degrees nose down, and negative G forces by the pilots - it was impossible to recover from that. The final act of MCAS, had it been a human pilot, for sure would be considered a saboteur, it's that ridiculous of a reaction under any circumstance, even had the airplane angle of attack been great enough to trigger MCAS it was a gross overreaction, at low altitude, commanding a path steeply below the horizon, and incompatible with survival. |
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If uncommanded trim motor action is forcing the airplane into a dangerous dive, it's runaway trim. The pilots must have thought it was runaway trim as they were desperately trying to counter it.
> So I reject the categorical claim they could have recovered with the flip of a switch.
But that's what did happen with the previous LA flight that landed safely.
> it was the only way to get electric motor assisted trim to try and get out of the mistrim.
That's right.
> But MCAS immediately triggered again
The electric trim switches override the MCAS.
So why didn't the EA pilots do that override? I don't know, neither do you. We'll have to see what the NTSB report says.