Originally Posted by
Europa01
If holding the trim wheel against rotation from the stab motor stops HS movement then that is the torque at which the clutch disengages - this will be the maximum torque the stab motor can exert.
I don't think this is correct. There are a lot of posts in various threads to look through, so forgive me for being lazy and not quoting the exact one, but a while ago I did see an explanation like this:
The clutch mechanism is such that even a relatively small opposing force on the trim wheel (such a pilot grabbing the wheel without the handle) will engage the clutch. However, absent any resistance of the wheel, the electric trim motor can drive the jackscrew itself with very high torque and against a high resistance; far more than a human could.
This implies that the mechanism distinguishes between resistance from the wheel versus resistance from the jackscrew, yet still maintains direct correspondence between the wheel and jackscrew motion.
It's not immediately obvious to me how such a mechanism would be designed, but I don't doubt that it is possible to design one given sufficient smarts. Can someone confirm that this is how it actually works on a 737?