Abstract: A fuel system comprises a fuel actuation arrangement 28 operable to split a metered flow of fuel into at least a first stream and a second stream, a control unit 25 controlling the operation of the fuel actuation arrangement 28, and wherein the control unit 25 controls the operation of the fuel actuation arrangement 28 in response to the output of a temperature sensor 34 sensitive to a gas temperature downstream of the high pressure compressor 14 of an associated engine and the output of a gas sensor 24 sensitive to at least one parameter of the composition of a gas downstream of a combustor 15 of the engine.

Abstract: A fuel system comprises a supply unit operable to deliver a metered supply of fuel to a supply manifold, a staging valve operable to control the supply of fuel from the supply manifold to a pilot outlet and a main outlet, and control means operable to control the operation of the staging valve to control whether fuel is delivered through the pilot and/or main outlet thereof.

Abstract: An aircraft fuel pumping arrangement comprises a first fuel pump, an electrically powered motor operable to drive the first fuel pump to deliver fuel to an outlet, a second fuel pump, a gas driven turbine operable to drive the second fuel pump to deliver fuel to the outlet, and a controller operable to control the operation of the gas driven turbine to determine the rate at which the second fuel pump is driven.

Abstract: A fuel staging system is described which comprises a staging valve 28 operable to divide a metered fuel supply between a pilot delivery line 18 and a mains delivery line 16, and a recirculation valve 54 connected to the mains delivery line 16 and operable to permit a recirculation fuel flow to be supplied to the mains delivery line 16 when the staging valve 28 occupies a position in which substantially no fuel is delivered to the mains delivery line 16 through the staging valve 28.

Abstract: A method of controlling the operation of a fuel metering unit of the type incorporating a temperature sensor is disclosed, the method comprising the steps of: sensing a change in temperature; using the sensed change in temperature to derive a fast temperature correction factor; using the sensed change in temperature to derive a slow temperature correction factor; using the fast and slow temperature correction factors in combination with a fuel demand to determine a metering valve position; and moving the metering valve to the determined metering valve position.

Abstract: A fuel metering unit (FMU) comprising a metering valve operable to control the supply of fuel to a delivery chamber of a pressure raising valve (PRV), the PRV including a valve member movable under the influence of the pressure within the delivery chamber between a closed position and an open position in which fuel is able to flow from the delivery chamber to an outlet port, and a push piston movable under the influence of the pressure within a control chamber to urge the valve member towards its open position, wherein the control chamber communicates with a valve control port.

Abstract: A shut-down arrangement comprises a shut-off actuation device operable under the control of a control unit, a switch whereby a first shut-down signal can be supplied to the control unit and whereby a second shut-down signal can be supplied to the shut-off actuation device, and delay means whereby the transmission of the second shut-down signal to the shut-off actuation device is delayed relative to the transmission of the first shut-down signal to the control unit.

Abstract: A staging valve arrangement is described that comprises an arrangement of electrically driven staging valves that are located, in use, in the high temperature core zone of an engine. Each staging valve may comprise a housing having an inlet, a pilot flow outlet and a mains flow outlet, a valve member movable between a closed position in which the mains flow outlet is closed and an open position in which the mains flow outlet is open, a motor operable to drive the valve member for movement, and a cooling arrangement.