Originally Posted by
yoko1
3. Trimming forces. Speaking as someone who has actually used the manual trim wheel on the Boeing, I can assure you that the trim resistance increases in both directions. It is not like rolling a boulder uphill where it is very difficult in one direction and easy in the other. The increased resistance is due to binding forces at the jackscrew thread/nut interface. Not sure if it is strictly frictional force or some type of deformation or misalignment. Keep in mind that while the aerodynamic forces are acting roughly parallel to the jackscrew body, those forces are mostly perpendicular at the thread/nut interface. There will be some directional bias, but that is a relatively small component. BTW, this is one of the reasons why a jackscrew mechanism is used in the first place - to minimize those directional forces and make it easier for the motor. However, one point needs to be emphasized again: You completely avoid these issues by not letting the stab get out of trim in the first place. .... And yes, by not being attentive to such matters, it is absolutely possible to place the aircraft in a state where things don't work as they should.
Yeah! That's right - you should NEVER let anyone(THING) trim the damned aeroplane ever further away from the correctly trimmed position. And you CERTAINLY would NEVER want to have anything SECRET, which pilots MUST NOT know about doing it SECRETLY and QUIETLY in the background whilst a badly designed and badly implemented system shakes the yoke violently whilst giving a number of other distracting URGENT warnings that you're stalling to steal your full attention and consume all you resources, leaving you nothing left to look out for any curved balls that Boeing snuck into the system secretly, which will effectively kill you and all aboard in a meter of a few tens of seconds, now would you?
Avoiding that nasty little killer should be avoided at all costs. What silly pilots, for "
not being attentive to such matters". Shame on you Yoyo, shame on you, Boeing.