The invention relates to an actuator comprising a cylinder (1) in which a rod (2) is mounted to slide, the actuator having a screw (8) extending inside the rod to co-operate with a nut (7) secured to the rod, the screw being driven in rotation by a motor (10), the actuator being characterized in that a hydraulic chamber (CH) filled with hydraulic fluid is arranged inside the actuator by means of a floating piston (20) sliding in sealed manner against the rod inside of the actuator, the hydraulic chamber being in fluid flow communication with an accumulator (21) via a solenoid valve (22) that is controllable between a closed state in which the chamber is isolated from the accumulator, and a fluid-passing state in which the hydraulic chamber and the accumulator are in communication, calibrated resistance being exerted against the passage of fluid from the chamber towards the accumulator.