Originally Posted by
david340r
I have read the whole thread and I'm still a bit puzzled about the relative ability to trim electrically or manually. It's been asserted several times that the electric trim is more powerful than manual trimming, but we also have the checklist item "grasp and hold" if isolating electric trim doesn't control a runaway. This has been touched on earlier, but I can't envision a simple way that the manual trim wheels could win against the electric motor (stall it) whilst then not being able to actually trim over a wider range of conditions than the electric trim. Can anyone confirm there is some form of mechanism to achieve this and provide any information as to how it works?
My understanding is that the 'grasp and hold' would be for the case of failed brakes on the stab mechanism, it is a recirculating ball drive so can be back driven by aero loads
Manual wheel inputs actuates a clutch that disconnects the motor so you would not be driving or trying to stall it. (motor may be unclutched when not active as well).
Not sure of mechanics of that but easy enough to conceive of a 'tension in cable' mechanism that would actuate the disengage.
Whether my details are exactly correct does not matter much since the point is that one is not directly fighting the motor, just trying to move the stab.