Re:Boeing Withheld Information on 737 Model, According to Sa...
by FabHK on Tuesday November 13, 2018 @04:13AM
(#18439685)
Yes, and in particular it seems likely that the pilots could have stopped the automatic down trim by either invoking two trim cutout switches, and/or manually holding/turning back the trim wheel. But it appears they a) had many other things to deal with, and b) did not expect this particular failure mode, so did not recognise it. Terrible.
Re:Boeing Withheld Information on 737 Model, According to Sa...
by comex on Tuesday November 13, 2018 @04:11AM
(#18439676)
You seem to be right:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/...
> Runaway Stabilizer
> 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.
See http://www.b737.org.uk/flightcontrols.htm
The pitch trim can be controlled by a number of different systems for different reasons, see the section on mach trim for an interesting one. I would be shocked if the inputs here weren't disabled by switching thd stab trim - autopilot switch to the off position.
I've mentioned in previous comments, this sounds like a trim runaway incident. The mechanism may be new but the underlying fault and the symptoms would have been the same.