The invention relates to an actuator (4) for controlling a flight control surface (3) of an aircraft, comprising:—a primary route (5) comprising a first member (8) for generating a first torque, and a first drive shaft (10) having an end (18) able to be connected to the first member (8) and an end (19) able to be connected to the control surface (3),—a secondary route (6) comprising a second member (24) for generating a second torque and a second drive shaft (26) having an end (45) able to be connected to the second member (24) and an end (46) able to be connected to the control surface (3), in which actuator the second drive shaft (10) is hollow and extends around the first drive shaft (26).