Abstract: A dual channel actuator for regulating control surfaces of an aircraft such as a helicopter. Primary and secondary channels are coupled by a differential gear. An internal stop in the differential gear limits the short term range of travel or authority of the primary channel. The secondary channel allows extended long term authority by recentering the reference point about which the rotational range of the primary channel is determined. A servo motor and primary input gear of the differential gear comprise the primary channel. A second servo motor and secondary input gear comprise the secondary channel. The reference point comprises a stop pin coupled with said differential gear.

Abstract: A switch structure detects acceleration in a preselected direction such as, for example, along the pitch axis of an aircraft. The switch has a spring supported mass urged toward a stable centered position within the switch housing. Acceleration displaces the mass such that it trips a spring wire switch mechanism for controlling such avionic devices as the autopilot system of the aircraft. A pair of solenoid coils are wound around the spring mass system on opposite sides of the centered position of the mass. The switch may be preflight tested by successively energizing the solenoid coils to attract the mass toward the centers of the solenoid fields, thereby artifically displacing the mass against the spring wire switches.