Hydraulic control circuit for controlling fan blade pitch

A hydraulic control circuit of a double-acting orientation cylinder to orient fan blades of a turbojet engine, comprising an oil tank, a variable-displacement axial piston pump including a swash plate as well as a control chamber and a compensation chamber, the tilt of the plate being controlled by pressurising these chambers, the pump being supplied by the tank and having the outlet thereof configured to be able to be connected by a supply pipe to one of the chambers of the orientation cylinder, the other chamber of the orientation cylinder being connected to the tank, the control chamber and the compensation chamber both being pressurised with a pressure corresponding to the pump outlet pressure, the control chamber and the compensation chamber being arranged to increase the tilt of the plate in order to increase the displacement of the pump when the pressurisation pressure of these chambers increases, wherein the pump has the outlet thereof connected to a dispensing valve via the supply pipe, wherein the compensation chamber of the pump is supplied by the output of the pump, wherein the two chambers of the orientation cylinder are connected to the dispensing valve, wherein the dispensing valve can occupy a position in which it connects one of the chambers to the supply pipe and the other chamber to the tank, or another position in which it connects one of the chamber to the tank and the other chamber to the supply pipe, the circuit further comprising a selection valve connected to the two chambers of the orientation cylinder and to the control chamber via a control pipe, to pressurise the control chamber of the pump with the highest pressure among the two chambers of the orientation cylinder.