Abstract: An actuator system for use in symmetrically positioning of control surfaces on opposite sides of an aircraft includes a primary load path for providing power to ball-screw mechanisms for moving the control surfaces between extended and retracted positions. A separate backup shaft is drivingly connected between opposite ends of the primary load path and, in normal service use, is unloaded. In the event of a failure in the primary load path, torque is transmitted through the backup shaft from the unaffected end of the primary load path so as to provide power for actuation of the ball-screw mechanism which otherwise would be affected by the failure in the primary load path. The backup shaft includes a one-piece continuous core whose axis is spaced laterally from the longitudinal axis of the primary load path to increase serviceability, reliability and reduce the likelihood of simultaneous damage to both the backup shaft and the primary load path.