Abstract

An actuator system for controlling the position of an aerodynamic control surface of an aircraft, such as an aileron, is disclosed. An actuator (12) having an output shaft (14) is mounted to a frame attached to the aircraft structure. A hydraulic coupling (32) is mounted on one side to the output shaft (14) of the actuator (12) and the other side to the control surface (50) and comprises a hydraulic cylinder (34) having a sealing member (36) movably mounted therein dividing the cylinder (34) into two portions (38, 40). The output shaft (14) of the actuator (12) is coupled to the cylinder (34) and an output shaft is attached to the sealing member (36) at one end and at its opposite end to the control surface or vice versa. A connecting tube (54) is provided coupling the two portions of the hydraulic cylinder together. The tube incorporates a valve (58) having a first position sealing off the two portions from each other and a second position providing a passageway therebetween. Thus, if the actuator (12) is working and the valve (56) is closed, an essentially solid connection is achieved between the actuator (12) and the control surface (50), thus allowing the actuator to move the control surface upon command. Should the actuator fail, the valve (56) can be opened, allowing fluid to flow from portion to portion. Thus, a redundant actuator can continue to control the position of the control surface while the disabled actuator is effectively decoupled from the control surface for the piston (36) will just move back and forth within the cylinder (34) as the control surface moves.