Fuel feed circuit with hydraulic actuator and fuel metering unit for an aeroengine

1. A fuel feed circuit for an aeroengine, the circuit comprising:

a low-pressure pumping system connected to a high-pressure pumping system by a low-pressure feed line, the high-pressure pumping system including first and second positive displacement pumps provided in parallel and driven simultaneously by the aeroengine to deliver fuel at high pressure to combustion chamber injectors and to actuators for actuating variable-geometry members of the aeroengine, each of the pumps including an inlet branching from an outlet of the low-pressure feed line at a substantially similar pressure;

a hydraulic actuator including a feed orifice connected to an outlet of the first pump, a high-pressure delivery orifice connected to an outlet of the second pump, and a low-pressure delivery orifice connected to the low-pressure feed line by a fuel return pipe, the feed orifice configured to be connected to the high-pressure delivery orifice at a first position of a slide of the hydraulic actuator or to the low-pressure delivery orifice at a second position of the slide of the hydraulic actuator; and

a fuel metering unit including a slide configured to slide a cylinder and carrying first, second, and third bearing surfaces subdividing the inside volume of the cylinder into first and second control chambers situated at ends of the cylinder and connected to a servo-valve, and first and second through sections situated between the bearing surfaces, the first through section being connected to an outlet of the high-pressure pumping system and leading to the combustion chamber injectors, the second through section being connected to the outlet from the high-pressure pumping system and leading to a high-pressure pilot chamber of the hydraulic actuator via an outlet orifice,

wherein the actuator includes a low-pressure pilot chamber that is connected to the fuel return pipe, the pressures applied in the high-pressure and low-pressure pilot chambers of the actuator opposing each other to control movement of the slide of the actuator,

wherein the servo-valve acts on the pressures in the high-pressure and low-pressure pilot chambers such that the outlet orifice is masked or uncovered and the slide of the hydraulic actuator moves between the first position and the second position, and

wherein, when the slide of the hydraulic actuator is in the first position, outlet flows from the first and second pumps are combined to flow to the combustion chamber injectors and to the actuators for actuating the variable-geometry members of the aeroengine, and when the slide of the hydraulic actuator is in the second position, all of the outlet flow of the first pump is discharged to the fuel return pipe without flowing to the combustion chamber injectors and to the actuators for actuating the variable-geometry members of the aeroengine.

2. A circuit according to claim 1 , wherein the high-pressure pilot chamber of the hydraulic actuator communicates with an intermediate pilot chamber connected to the fuel feed circuit upstream from the low-pressure pumping system, and includes a spring located in the intermediate pilot chamber.

3. A circuit according to claim 1 , further comprising a fuel return line connecting the outlet from the high-pressure pumping system to the low-pressure feed line, and a regulator valve positioned on the fuel return line.

4. A circuit according to claim 1 , further comprising a check valve positioned between the high-pressure delivery orifice of the hydraulic actuator and the outlet of the second pump.

5. A circuit according to claim 1 , wherein the first pump has pumping capacity greater than that of the second pump.

6. An aeroengine including a fuel feed circuit according to claim 1 .