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by EdiX
2366 days ago
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Broadly speaking, I agree with you. I was responding to the hysteria about the trim wheel in this thread. I'm getting the impression that some users think the trim wheel, or its behavior under extreme aerodynamic conditions, is a "new" design flaw unique to the 737 MAX when in fact almost every airliner in existence has a trim wheel behaves like that. The exception being modern fly-by-wire planes that simply don't have an option of manual override. The speaker talks about trimwheel behaviour. Pilots train for runaway stabilizer trim, but that's continuous movement of the trimwheel, faulty MCAS looks much like regular speedtrim
Empirically, the Lion Air plane exhibited the same MCAS behavior on its last (successful) flight. So it's at least possible for pilots to recognize it as a runaway trim and act accordingly. Obviously you shouldn't take Lion Air, but after this talk Boeing doesn't look safe now either.
After reading the Lion Air report my conclusion is that the MCAS was poorly designed but it's also an easily fixed problem on an otherwise safe design and there's so much focus on boeing that they will take action and fix it. Meanwhile nobody cares about Lion Air and if they keep flying broken airplanes eventually they're going to kill more people, with or without MCAS. |
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Also, the AoA-vane was replaced with a faulty part, and never retested after install if I recall correctly. A procedure complicated by the fact the plane would have had to have been started, shutdown, then restarted since the Flight Computer switches from side-to-side each flight.
So a maintenance tech may have accidentally tested the wrong computer assuming the documentation wasn't up to snuff. Can't say as I've seen that part of the documentation myself; but considering they left MCAS out of the pilot docs, I somehow doubt that it was greatly elaborated on in the maintenance docs as well.