Abstract: A system uses a two-stage electrohydraulic servo valve that includes an additional control port that commands a fail-fixed valve to lock the position of a device in the last commanded position. The additional port is modulated by an existing land on the EHSV valve element, adding little to no complexity. Major technical benefits of the disclosed system are that it adds little to no cost, complexity, size, or weight the device being controlled. The disclosed configuration allows for the use of a relatively small and simple fail-fixed valve, and the control ports on the controlled device keep “drift” to a minimum, when transitioning between normal operating mode and fail-fixed operating mode.

Abstract: A system uses a two-stage, four-way electrohydraulic servo valve that includes an additional control port that commands a fail-fixed valve to lock the position of a device in the last commanded position. The additional port is modulated by an existing land on the EHSV valve element, adding little to no complexity. Major technical benefits of the disclosed system are that it adds little to no cost, complexity, size, or weight the device being controlled. The disclosed configuration allows for the use of a relatively small and simple fail-fixed valve, and the control ports on the controlled device keep “drift” to a minimum, when transitioning between normal operating mode and fail-fixed operating mode.

Abstract: A propeller oil control system for a turboprop engine of an aircraft includes an engine control unit and a propeller oil controller. The engine control unit is operable to determine a flight phase of the aircraft and is configured to supply control commands. The propeller oil controller is coupled to receive a supply of oil and to discharge the oil at a discharge oil pressure. The propeller oil controller includes an electrohydraulic servo valve that receives the control commands moves to a plurality of positions between a first position and a mid-position, and a plurality of positions between the mid-position and a second position. The engine control unit only commands the electrohydraulic servo valve to move out of the first position when the engine control unit determines the aircraft is conducting a take-off roll or the aircraft is in flight.

Abstract: Embodiments of a combined overspeed and fuel stream selector system are provided. In an embodiment, the assembly includes a conduit network, a Discharge Select Valve (DSV), and a shutoff valve. The DSV is fluidly coupled to a primary fuel inlet, a secondary fuel inlet, and a primary fuel outlet included in the conduit network. The shutoff valve is fluidly coupled between the primary fuel inlet and the primary fuel outlet. In a standard operation mode, the shutoff valve is maintained in an open position, while fuel received at the primary fuel inlet is directed through the shutoff valve, through the DSV, and to the primary fuel inlet. Conversely, in a backup operation mode, the shutoff valve is closed to block fuel flow from the primary fuel inlet to the primary fuel outlet, while the DSV directs fuel flow received at the secondary fuel inlet to the primary fuel outlet.

Abstract: A propeller pitch control system for a turboprop engine of an aircraft includes an engine control unit and a pitch control unit. The engine control unit is operable to determine a phase of flight of the aircraft and is configured to supply control commands. The pitch control unit is coupled to receive the control commands from the engine control unit and includes a housing, a beta piston, a position sensor, a beta tube, and an electrohydraulic valve. The engine control unit only commands the electrohydraulic valve to move the beta piston from the fully retracted position when the engine control unit determines the aircraft is conducting pre-takeoff roll taxiing operations or is conducting post landing touchdown operations.

Abstract: A propeller pitch control system for a turboprop engine of an aircraft includes a negative torque sensor, a full feather control valve assembly, and a feather valve assembly. The feather valve assembly is responsive to fluid pressures from the negative torque sensor and the control valve assembly to move between a plurality of positions. An engine control unit or a manual user interface can also be used to control the position of the feather.

Abstract: A propeller pitch control system for a turboprop engine of an aircraft includes a negative torque sensor, a full feather control valve assembly, and a feather valve assembly. The feather valve assembly is responsive to fluid pressures from the negative torque sensor and the control valve assembly to move between a plurality of positions. An engine control unit or a manual user interface can also be used to control the position of the feather.

Abstract: A propeller oil control system for a turboprop engine of an aircraft includes an engine control unit and a propeller oil controller. The engine control unit is operable to determine a flight phase of the aircraft and is configured to supply control commands. The propeller oil controller is coupled to receive a supply of oil and to discharge the oil at a discharge oil pressure. The propeller oil controller includes an electrohydraulic servo valve that receives the control commands moves to a plurality of positions between a first position and a mid-position, and a plurality of positions between the mid-position and a second position. The engine control unit only commands the electrohydraulic servo valve to move out of the first position when the engine control unit determines the aircraft is conducting a take-off roll or the aircraft is in flight.

Abstract: A propeller pitch control system for a turboprop engine of an aircraft includes an engine control unit and a pitch control unit. The engine control unit is operable to determine a phase of flight of the aircraft and is configured to supply control commands. The pitch control unit is coupled to receive the control commands from the engine control unit and includes a housing, a beta piston, a position sensor, a beta tube, and an electrohydraulic valve. The engine control unit only commands the electrohydraulic valve to move the beta piston from the fully retracted position when the engine control unit determines the aircraft is conducting pre-takeoff roll taxiing operations or is conducting post landing touchdown operations.

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: Embodiments of a combined overspeed and fuel stream selector system are provided. In an embodiment, the assembly includes a conduit network, a Discharge Select Valve (DSV), and a shutoff valve. The DSV is fluidly coupled to a primary fuel inlet, a secondary fuel inlet, and a primary fuel outlet included in the conduit network. The shutoff valve is fluidly coupled between the primary fuel inlet and the primary fuel outlet. In a standard operation mode, the shutoff valve is maintained in an open position, while fuel received at the primary fuel inlet is directed through the shutoff valve, through the DSV, and to the primary fuel inlet. Conversely, in a backup operation mode, the shutoff valve is closed to block fuel flow from the primary fuel inlet to the primary fuel outlet, while the DSV directs fuel flow received at the secondary fuel inlet to the primary fuel outlet.

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 gas turbine engine fuel delivery system includes a mechanically-driven fuel pump, an electrically-driven fuel pump, and an engine control. The mechanically-driven fuel pump is adapted to receive a drive torque from a gas turbine engine draw fuel into its fuel inlet and discharge the fuel from its fuel outlet. The electrically-driven fuel pump has a first fuel inlet/outlet that is in fluid communication with the mechanically-driven fuel pump fuel inlet, and also has a second fuel inlet/outlet. The engine control is responsive to an engine start signal to cause the electrically-driven fuel pump to be temporarily energized to pump fuel from the first fuel inlet/outlet to the second fuel inlet/outlet, and is responsive to an engine shutdown signal to cause the electrically-driven pump to be temporarily energized to pump fuel from the second fuel inlet/outlet to the first fuel inlet/outlet.

Abstract: A two-position, two-stage servo valve includes a valve body, a valve element, a control pressure chamber, and a control element. The valve body has an inner surface that defines a valve element chamber that includes a first control chamber and a second control chamber. The first control chamber is larger than the second control chamber. The valve element has first and second ends and is disposed within the valve element chamber and is movable between a first valve position and a second valve position. The first end is larger than the second end and is disposed within the first control chamber, and the second end is disposed within the second control chamber. The control pressure chamber includes a control pressure port that is in continuous fluid communication with the first control chamber. The control element is movable between a first control position and a second control position.

Abstract: A gas turbine engine fuel supply system includes a primary gear pump and a secondary gear pump. The primary gear pump always actively delivers fuel to the downstream fuel system, and is sized to supply 100% of the burn flow needed at a select low demand condition. The secondary gear pump is sized to make up the remainder of the flow at high demand conditions, and actively delivers fuel to the downstream fuel system only during those conditions. To supply discharge fuel pressures in excess of gear pump capability, a supercharger pump is disposed upstream of the primary and secondary gear pumps. The supercharger pump is preferably activated only during high demand conditions as an additional energy conservation measure.

Abstract: A fuel supply system includes a fuel supply line, a fuel filter, a filter bypass line, a first differential pressure sensor, a second differential pressure sensor, and a filter bypass valve. The fuel filter is disposed in series in the fuel supply line to remove particulate from the fuel. The filter bypass line has a fuel inlet upstream of the fuel filter, and an outlet that is downstream of the fuel filter. The first differential pressure sensor continuously senses differential pressure across the fuel filter, and the second differential pressure sensor selectively senses differential pressure across the fuel filter. The filter bypass valve is movable between a first non-bypassing position and a second bypassing position and controls whether only the first differential pressure sensor or both the first and second differential pressure sensors sense the differential pressure across the fuel filter.

Abstract: A two-position, two-stage servo valve includes a valve body, a valve element, a control pressure chamber, and a control element. The valve body has an inner surface that defines a valve element chamber that includes a first control chamber and a second control chamber. The first control chamber is larger than the second control chamber. The valve element has first and second ends and is disposed within the valve element chamber and is movable between a first valve position and a second valve position. The first end is larger than the second end and is disposed within the first control chamber, and the second end is disposed within the second control chamber. The control pressure chamber includes a control pressure port that is in continuous fluid communication with the first control chamber. The control element is movable between a first control position and a second control position.

Abstract: A gas turbine engine fuel supply system includes a primary gear pump, a secondary gear pump, and a pump bypass valve. The primary gear pump always actively delivers fuel to the downstream fuel system, and is sized to supply 100% of the burn flow needed at a select low demand condition. The secondary gear pump is sized to make up the remainder of the flow at high demand conditions, and actively delivers fuel to the downstream fuel system only during those conditions. To supply discharge fuel pressures in excess of gear pump capability, a supercharger pump is disposed upstream of the primary and secondary gear pumps. The pump bypass valve is configured to regulate fuel pressure at the primary gear pump outlet to one of a plurality of preset differential pressures above one of a plurality of fuel load pressures and prevents reverse pressurization of the gear pumps.

Abstract: A gas turbine engine fuel delivery system includes a mechanically-driven fuel pump, an electrically-driven fuel pump, and an engine control. The mechanically-driven fuel pump is adapted to receive a drive torque from a gas turbine engine draw fuel into its fuel inlet and discharge the fuel from its fuel outlet. The electrically-driven fuel pump has a first fuel inlet/outlet that is in fluid communication with the mechanically-driven fuel pump fuel inlet, and also has a second fuel inlet/outlet. The engine control is responsive to an engine start signal to cause the electrically-driven fuel pump to be temporarily energized to pump fuel from the first fuel inlet/outlet to the second fuel inlet/outlet, and is responsive to an engine shutdown signal to cause the electrically-driven pump to be temporarily energized to pump fuel from the second fuel inlet/outlet to the first fuel inlet/outlet.

Abstract: A system provides “fail fixed” functionality and allows a user to manually manipulate fuel flow to a gas turbine engine in the unlikely event the primary control means is unavailable. The fuel metering unit includes a fuel metering valve, a flow increase valve, and a flow decrease valve. The flow increase valve and flow decrease valves are both in fluid communication with the fuel metering valve and are each adapted to selectively receive fuel flow commands from a primary fuel flow command source and from a secondary fuel flow command source. The flow increase and decrease valves are responsive to the fuel flow commands to selectively control the position of the fuel metering valve.