Originally Posted by
OldnGrounded
Hmmm, indeed. It's really inconceivable that friction between the jackscrew and the ball nut could even come close to the axial forces transmitted from aero loads on the stabilizer.
I was thinking that even axial forces could increase the friction between the ball nut and the screw. I know a ball nut has much lower friction compared to a regular nut, but I'm not sure how it would behave under large axial loads. But I could be wrong about that, and friction caused by axial loads might indeed be insignificant.
The problem is, if there is no significant friction increase when there is an axial load, then I would expect to be much easier to trim in the AND direction when you already have an AND mistrim. And the more out of trim you are, the easier it should be to apply more trim in the wrong direction. But Mentour's simulator video has shown otherwise, the more AND mistrim they had, the harder it became to trim AND (and ANU) manually.
Assuming the simulator replicates the behavior correctly, if it's not the friction in the nut that causes this behavior, then maybe the behavior is caused by some strange interaction with the braking mechanism that prevents the screw from being back driven.