Abstract: A fuel system (10) for a gas turbine engine (18) having a shaft (30) and requiring fuel to be supplied at a first rate for engine start up, the fuel system (10) including: a main fuel pump (14) for providing fuel to the gas turbine engine (18), the main fuel pump (14) having an output varying with shaft speed, the output being at a windmilling rate when the engine (18) is windmilling, the windmilling rate being less than the first rate; and an auxiliary fuel pump (40) for providing fuel to the gas turbine engine (18) and having an auxiliary output rate greater than or equal to the difference between the first rate and the windmilling rate. A method of operating such a fuel system (10) is also disclosed.

Abstract: A fuel control system for a gas turbine engine is disclosed that includes a flow path carrying fuel from a fuel source to a combustion chamber, an ecology valve 124 for removing a quantity of fuel from the flow path, the ecology valve 124 being shiftable in a first direction from a first position to a second position and in a second direction from said second position to said first position and a fuel line 115 connected between the flow path and the ecology valve 124 for moving fuel between the flow path and the ecology valve 124 to bias the ecology valve 124 toward the second position, where the fuel line 115 is configured, such as by the inclusion of an orificed check valve 150 therein, to allow fuel to move therethrough away from the ecology valve 124 at a greater rate than toward the ecology valve 124.

Abstract: A control for a hydraulic propeller pitch actuator includes a low power pilot valve responsive to digital electronic input signals to control movement of a hydraulic servomotor driving a higher power servovalve. Negative feedback motion is delivered from the servomotor to both the pilot valve and the servovalve.

Abstract: A large flow of high pressure fuel is supplied to a gas turbine engine by mounting a small modified vortex pump over or around a main high speed shaft. The pump includes a plurality of short, stubby impeller blades rotating at a very high speed within a fuel filled annular chamber having an axial fuel inlet and a tangential fuel outlet. A pump booster and priming system ensures the pump fills with fuel during operation.

Abstract: A metering valve (10) having a bi-directional motor (11) with a linearly-displaceable output shaft (21) in which the shaft (21) is separated from but cooperates with a bi-directionally movable piston (16) to provide a variable flow aperture (102) in a secondary flow path (12,52,74,78,76,102,100,48) extending axially through the piston (16). Flow along a primary flow path (12,18,48,14) is varied by movement of the piston (16) in response to an imbalance of opposing hydraulic forces. The imbalance in forces results from varying the foresaid flow aperture (102) by displacing the output shaft (21). However, the flow aperture (102) is only transitorily varied by displacement of the shaft (21) since the valve (10) is designed to provide a follow-up servo function by which the piston (16) is kept at a substantially constant distance from the shaft (21).

Abstract: A large flow of high pressure fuel is supplied to a gas turbine engine by mounting a small modified vortex pump over or around a main high speed shaft. The pump includes a plurality of short, stubby impeller blades rotating at a very high speed within a fuel filled annular chamber having an axial fuel inlet and a tangential fuel outlet. A pump booster and priming system ensures the pump fills with fuel during operation.

Abstract: A high speed liquid vortex pump is fitted with an electrically controlled needle valve assembly which modulates the pressure of a small portion of the working fluid which in turn moves a spool valve to regulate the high volume, high pressure pump output flow.

Abstract: A high speed liquid vortex pump is fitted with a flexible tube in the discharge throat. The flow area of the flexible tube, and thus the pump output flow rate, is varied by surrounding the tube with a pressure modulated stream of the working fluid.