A device (13) for detecting the breakage of a primary path in a flight control actuator, said actuator having a primary path (1) comprising a rotary hollow screw (2), a secondary path (10) comprising a safety rod (3) that reacts the load passing through the screw (2), said device (13) being characterized in that it comprises a position sensor (15), connected to the screw (2), to measure information representative of the angular position thereof, and a disconnection system (17) able to disconnect the screw (2) position sensor (15) in the event of relative movement of the rod (3) with respect to the screw (2) if there is a break in the primary path (1).