Abstract: A metering valve includes a valve body, a valve element, a rotary servo, and a stepper motor. The valve body has a valve chamber, a fluid inlet port, a fluid outlet port, a metering valve control pressure inlet port, a servo control pressure inlet port, and a servo control pressure outlet port. The valve element is movably disposed within the valve chamber and defines therein at least a control pressure chamber and a return pressure chamber. The valve element is responsive to fluid pressure in the control pressure chamber to move between a closed position and a plurality of open positions. The rotary servo is rotatable about a rotational axis to a plurality of servo positions to thereby vary fluid pressure in the control pressure chamber. The stepper motor is responsive to commands to rotate the rotary servo to a commanded servo position.

Abstract: A propeller pitch control actuation system includes a relatively lightweight, relatively inexpensive means for selectively preventing the propeller pitch control actuator from commanding reverse pitch positions.

Abstract: A propeller pitch control actuation system includes a relatively lightweight, relatively inexpensive means for selectively preventing the propeller pitch control actuator from commanding reverse pitch positions.

Abstract: A fuel control system for a gas turbine engine includes a metering valve for metering a flow of fuel, a throttling valve for maintaining a pressure drop across the metering valve, the throttling valve being shiftable between an open state and a shutoff state blocking an outlet of the metering valve, a primary control pressure supply for supplying a primary control pressure to the metering valve for controlling the position of the metering valve, a backup control pressure supply, a transfer valve shiftable between a first position connecting the primary control pressure to supply to the metering valve and a second position connecting the backup control pressure to the metering valve, and an electrohydraulic servovalve (EHSV) operably connected to the throttling valve and the transfer valve and controlling the state of the transfer valve and the position of the throttling valve. Also a method for controlling a transfer valve and a throttling valve.

Abstract: A fuel control system (10) for a gas turbine engine includes a main fuel inlet line (18), an auxiliary fuel inlet line (20) and an engine fuel outlet line (16). A first flow path extends from the main fuel inlet line (18) to the engine fuel outlet line (16) and a second flow path extends from the auxiliary fuel inlet line (20) to the engine fuel outlet line (16). A check valve (22) in the first flow path allows fuel flow through the first flow path in a direction from the main fuel inlet line (18) to the engine fuel outlet line (16) and substantially prevents fuel flow through the first flow path in a direction from the engine fuel outlet line (16) to the main fuel inlet line (18). The check valve (22) is shiftable between a first position connecting the auxiliary fuel inlet (20) to the engine fuel outlet (16) and a second position blocking the second flow path. Also a method of controlling fuel flow in a fuel control system of a gas turbine engine.

Abstract: An electro-hydraulic servovalve (EHSV) (10) that includes a nozzle (16), a motor (12) operably connected to the nozzle (16) for controlling the position of the nozzle (16) based on current provided to the motor (12), a spool (18) having first and second ends (22,26) slidably mounted in a sleeve (34) having first and second ends (31,33) and a first land (21) near the first end (22), a first passage (40) extending from near the nozzle (16) to the first end (31) of the sleeve (34), a second passage (42) extending from near the nozzle (16) to the second end (33) of the sleeve (34), the spool (18) shifting to a first fail-safe position when the current is below a first predetermined level and latching in a second fail-safe position different than the first fail-safe position when the current exceeds a second predetermined level greater than the first predetermined level.

Abstract: A valve assembly having a position control characteristic that is represented by an N-th order polynomial equation includes a valve housing a valve element, and a valve characterization circuit. The valve housing has at least a fluid inlet, a fluid outlet, and a flow passage between the fluid inlet and fluid outlet. The valve element is mounted on the valve housing, is disposed at least partially within the valve housing flow passage, and is movable between a closed position and an open position. The valve characteristic circuit is mounted on the valve housing, and includes a plurality of resistors. Each resistor has a resistance value representative of at least one digit in the N-th order polynomial equation.

Abstract: A valve assembly having a position control characteristic that is represented by an N-th order polynomial equation includes a valve housing a valve element, and a valve characterization circuit. The valve housing has at least a fluid inlet, a fluid outlet, and a flow passage between the fluid inlet and fluid outlet. The valve element is mounted on the valve housing, is disposed at least partially within the valve housing flow passage, and is movable between a closed position and an open position. The valve characteristic circuit is mounted on the valve housing, and includes a plurality of resistors. Each resistor has a resistance value representative of at least one digit in the N-th order polynomial equation.

Abstract: A gas turbine engine fuel system (10) that includes a fuel line, a pressurizing valve (14) in the fuel line having a burn fuel outlet (16) to a burn fuel line (18) providing burn fuel to the engine (20) and a control fuel outlet (22) to a control fuel line (24) providing pressure for controlling an engine system (26), the pressurizing valve (14) being shiftable between a closed position blocking fuel flow to the burn fuel line (18) and to the control fuel line (24) and a second position, and a secondary flow valve (30) having a first end (44, 64) in fluid communication with the burn fuel line (18) downstream of the pressurizing valve (14) and a second end (64, 66) in fluid communication with the control fuel line (24) downstream of the pressurizing valve (14), the secondary flow valve (30) controlling the addition of a secondary fluid flow from a secondary fluid line (32) to the control fuel line (24), the secondary flow valve (30) substantially preventing the secondary flow from reaching the secondary flow v