Abstract: A fuel system comprises a pressure raising valve operable to control communication between a fuel delivery line and an engine manifold line, and an ecology valve comprising a piston movable within a bore, the piston and bore together defining a control chamber and an ecology chamber, the ecology chamber communicating with the engine manifold line, the pressure within the control chamber being controllable to control the position occupied by the piston, the ecology valve further comprising seal means whereby, when the piston occupies a first position in which it engages the seal means, only a first, relatively small, effective area of the piston is exposed to a fuel pressure within the engine manifold line, a second, larger, effective area being exposed to the fuel pressure within the engine manifold line when the piston occupies a position in which it does not engage the seal. An ecology valve for use in the fuel system is also described.

Abstract: A fuel system comprises a pressure raising valve operable to control communication between a fuel delivery line and an engine manifold line, and an ecology valve comprising a piston movable within a bore, the piston and bore together defining a control chamber and an ecology chamber, the ecology chamber communicating with the engine manifold line, the pressure within the control chamber being controllable to control the position occupied by the piston, the ecology valve further comprising seal means whereby, when the piston occupies a first position in which it engages the seal means, only a first, relatively small, effective area of the piston is exposed to a fuel pressure within the engine manifold line, a second, larger, effective area being exposed to the fuel pressure within the engine manifold line when the piston occupies a position in which it does not engage the seal. An ecology valve for use in the fuel system is also described.

Abstract: A fuel control system for controlling the supply of fuel to an engine, the control system comprising: pump means for providing a flow of fuel to said engine; first and second drive means for driving said pump means; and, control means for controlling said first and second drive means; wherein, said control means is arranged to control said first and second drive means such that in the event of failure of one of said first and second drive means, said pump means is driven by the other of said first and second drive means.

Abstract: A fuel control system for controlling the supply of fuel to an engine, the control system comprising:

Abstract: A fuel control system for an engine, laving a pup operable to supply an output flow of fuel, engine fuel flow regulation means operable to regulate the pump output flow, and pump control means operable to vary an output rate of the pump according to an operational condition of the engine fuel flow regulation means.

Abstract: A fuel control system for an engine, having a pump operable to supply an output flow of fuel, engine fuel flow regulation means operable to regulate the pump output flow, and pump control means operable to vary an output rate of the pump according to an operational condition of the engine fuel flow regulation means.

Abstract: A fuel control system for an engine, having a pump operable to supply an output flow of fuel, engine fuel flow regulation means operable to regulate the pump output flow, and pump control means operable to vary an output rate of the pump according to an operational condition of the engine fuel flow regulation means.

Abstract: A fuel control system for a gas turbine engine having a plurality of burner manifolds, comprising a spill valve for spilling excess fuel from a high pressure fuel supply line and a plurality of control arrangements, each of which is arranged to control fuel flow rate to a respective one of the manifolds and comprises a metering valve and a regulator for regulating the pressure drop across the metering valve, the spill valve having a cylinder containing a piston which is movable to close the spill valve and each of the regulators having a valve for connecting the cylinder of the spill valve to high pressure fuel when the pressure drop across the metering valve is less than a predetermined value.

Abstract: An electronic fuel control for a gas turbine engine having a gas generator and a separate power turbine includes gas generator and power turbine actual speed transducers, gas generator and power turbine desired speed signal generators, error amplifiers connected to the respective transducers and generators, a "low wins" gate for selecting the lower error, an acceleration control limiter passing the selected signal from the gate to an integrator and an output difference amplifier producing an output signal determined by the difference between the integrator output and that of the gas generator transducer to control the fuel flow to the engine.

Abstract: An electronic fuel control for a gas turbine with a power turbine engine includes a power turbine actual speed transducer, a power turbine desired speed control and a control circuit including an output difference amplifier the output of which determines the quantity of fuel supplied to the engine. To guard against failure of the transducer a "high wins" gate receives signals from the transducer and the amplifier and a second difference amplifier has its two inputs connected to the gate and to the transducer via an attenuator so that in normal running conditions the output of the output amplifier is less than that of the transducer but more than that of the difference amplifier.