RE JACKSCREW- EG BALLSCREW - being backdriven -- PLEASE SEE MY POST 1522 this thread
Quote:
Originally Posted by
DaveReidUK 
Correct me if I'm wrong, but the
coarser the thread pitch (all other things being equal), the
more likely a jackscrew is to be back driveable (the spiral ratchet screwdriver principle). Is that what you're saying?
I can't see air loads on the stab being capable of overcoming the combined braking friction in the jackscrew, gearbox and actuator unless we're talking about a previously undisclosed failure in addition to the issues already discussed.
Its MORE than just the pitch ( lead) please take the time to read this simplified explanation
https://www.linearmotiontips.com/how...ll-back-drive/
and for an approximation of loads
https://www.aerospaceonline.com/doc/...actuators-0001
+++++++
Originally Posted by
DaveReidUK
Maybe it can, maybe it can't (my money would be on not).
But either way - what is the relevance?
Given the overwhelming evidence implicating the STS/MCAS, why are we throwing Occam's Razor out of the window and postulating an unrelated, independent mechnical failure of the actuation mechanism as a causal factor?
The MAX has the same horizontal stabilizer as the NG, and I'd bet that the actuator/gearbox/jackscrew isn't significantly different either. How many NG loss of pitch trim control incidents have there been in the last 20 years that have been attributable to actuation failure?