Abstract: A servovalve system comprising a pilot stage valve in communication with an hydraulic stage valve, the hydraulic stage valve comprising a valve member movably mounted in a valve chamber to selectively meter fluid flow in a flow path from an upstream inlet port to a downstream outlet port and at least two variable-sized orifices disposed in the flow path between the inlet and outlet ports, an upstream pressure sensor, a downstream pressure sensor, a fluid temperature sensor, a position sensor sensing a linear position of the valve member, a controller that receives input from the upstream pressure sensor, the downstream pressure sensor, the fluid temperature sensor and the position sensor; and the controller configured to provide a control signal to the pilot stage valve as a function of the input from the upstream pressure sensor, the downstream pressure sensor, the fluid temperature sensor and the position sensor.

Abstract: A servovalve system comprising a pilot stage valve in communication with an hydraulic stage valve, the hydraulic stage valve comprising a valve member movably mounted in a valve chamber to selectively meter fluid flow in a flow path from an upstream inlet port to a downstream outlet port and at least two variable-sized orifices disposed in the flow path between the inlet and outlet ports, an upstream pressure sensor, a downstream pressure sensor, a fluid temperature sensor, a position sensor sensing a linear position of the valve member, a controller that receives input from the upstream pressure sensor, the downstream pressure sensor, the fluid temperature sensor and the position sensor; and the controller configured to provide a control signal to the pilot stage valve as a function of the input from the upstream pressure sensor, the downstream pressure sensor, the fluid temperature sensor and the position sensor.

Abstract: A method of starting gas turbine engine (17) having a variable-speed motor-driven pump (13) operatively arranged to supply a source of fuel to the engine through at least one combustor nozzle (19) when the engine is operating normally, includes the steps of: providing a calibration orifice (16) sized to simulate the pressure-flow characteristics of the nozzle; initially directing the flow from the pump through the orifice; operating the pump at preselected speeds; measuring the temperature of the flow at each of such speeds; measuring the pressure drop of the flow across the orifice at each of such speeds; calculating the fuel mass flow rate as a function of pump speed and temperature; thereafter redirecting the flow from the orifice to the nozzle; and subsequently controlling the speed of the pump to produce a desired fuel mass flow rate for starting the engine.