An electromechanical actuator for a movable flight control surface of an aircraft, the actuator comprising an electric motor having an outlet shaft (20) with first and second directions of rotation, a movement transmission (1) arranged to connect the outlet shaft of the motor to the movable flight control surface, and a control unit (3) for controlling the motor, the actuator being characterized in that the transmission incorporates a pawl device (18) arranged to oppose the transmission of movement in the first direction of rotation, and in that the control unit is connected to a pawl declutching member (19) for declutching the pawl and enabling movement to he transmitted in the first direction of rotation.