An electric trim motor and actuator arrangement provides movement of the stabilizer. Aircraft that use a movable horizontal stabilizer for longitudinal control trim do so by varying the neutral position of the control linkage, which, in turn, moves the surface. For example, longitudinal trim is provided by varying the position of the artificial-feel bungee, repositioning the linkage, and setting up a new neutral position for the stabilizer linkage. Anytime a new neutral is introduced by the trim actuator, the power valve shuttle is displaced. The stabilizer assumes a new neutral location, changing Figure 9-42.
Aileron trim control system.
The trim inputs may be provided by the pilot or the automatic flight control system. The actuator has two operating speeds-high speed for manual trim and low speed for AFCS trim. Directional Trim Directional trim is necessary to compensate for yaw of the aircraft. Rudder trim is basically similar to the aileron trim. When the momentary throw rudder trim switch moves left or right, the trim actuator energizes to move the load-feel bungee, repositioning the rudder power mechanism input crank.