Abstract: Disclosed is an improved device to control and regulate the opening and closing of a cross section of a turbojet propulsive nozzle having at least one hydraulic cylinder acting on at least one movable flap element. The invention includes a first system to supply the cylinder with hydraulic fluid under pressure for normal operation and a second supply system to be used in an emergency. The elements for changing from the normal operation to an emergency operation are combined with the elements to generate in the hydraulic cylinder a differential pressure, such that the cross section of the nozzle assumes an intermediate position assuring sufficient thrust for the engine, while avoiding the danger of overloading the compressor. The system is effected automatically when the pilot actuates the emergency supply system.