Abstract: A rotary actuator (18) is provided, including an actuator assembly (20). The actuator assembly includes a torque tube (24) formed of a shape memory alloy, a super elastic NiTinol return spring (26) having a proximal end (46) and a distal end (44), and a torque tube heating element (30) positioned near the torque tube. The torque tube (24) includes a proximal end (32) and a distal end (34). The return spring and torque tube are connected at their ends, with the torque tube being pretwisted while in a martensitic state relative to the spring. Activation of the heating element causes the torque tube to enter an austenitic state in which it returns to its previous untwisted configuration. Removal of heat allows the torque tube to return to a martensitic state, further allowing the return spring to retwist the torque tube. Further provided is a unique locking assembly (22) for use with the actuator assembly.