Originally Posted by
Takwis
False. The classic stab trim runaway is a stuck, or fused switch, which causes the trim to run "continuously", to the limits of the jackscrew in one motion. The characteristics of an MCAS input are actually closer to those of the STS, i.e. intermittent running of the trim, starting and stopping. Pilots that fly the 737 are very used to the STS trimming in the background on departure, and generally ignore it. MCAS is "identical" to neither situation, but closer to "STS running backward", as the surviving crew noted in the logbook.
There is a very good thread in the tech section, I suggest you educate yourself by going to read through it:
B-737 Speed Trim System
Really? Show me where in the Boeing manuals that a Stab Trim Runaway is a case where the trim runs continuously to the limits of the jackscrew?
And how, as a pilot if you are a pilot, are you to determine if the trim reaches the jack screw or not? I would also suggest that any competent pilot will react to a trim runaway long before it reaches the jack screws.
Or would you just watch it run continuously, pitch the nose down 40 degrees then wait until it stops (at the jackscrew limit if you determine that) and then say "This must be a stab trim runaway as I think it has now reached the jack screws".
Or would you just watch it run continuously, pitch the nose up 40 degrees then wait until it stops (at the jackscrew limit if you determine that) and then say "This must be a stab trim runaway as I think it has now reached the jack screws"
Or would you cut the stab trim out after maybe 5 degrees of nose down (or up) attitude and recover
I know what I would do.
According the the NNC, a Runaway Stabilizer is defined as: Uncommanded stabilizer trim movement occurs continuously. STS is commanded trim, for those that are shown it in training and is a perfectly normal trim response. How do you define continous? 1 second, 5 seconds, 10 seconds, a 60 seconds?
As far as educating myself on the trim system, I have 16 years of B737 experience. How about you?