Abstract: In an aircraft in which servocontrols are supplied with hydraulic fluid under pressure by a main pump driven by an engine of the aircraft and, in the event of loss of said engine power, by an emergency pump which is driven by a dynamic air pressure turbine deployed from the fuselage of the aircraft, a system is provided for assisting the restarting of said engine in the event of said aircraft suffering a total loss of engine power, wherein said main pump is of the reversible kind and means are provided for enabling surplus hydraulic power from the emergency pump to be supplied to the main pump whereby the latter acts as a hydraulic motor to increase the windmilling speed of the dead engine and thereby facilitate re-ignition thereof, even at a low aircraft speed.