Adjustable tailplane
Many aircrafts are fitted with variable incidence horizontal tailplane. Considering a mechanical controlled airplane, I can't understand if, to trim the aircraft at a certain speed, only the taiplane is rotated, with the elevator that is perfectly aligned with it (but in this case the hinge moment on the elevator is not zero) or if also the elevator is rotated, with respect to the tailplane, so to cancel the hinge moment and relieve the force on the yoke.