Abstract: A combustion staging system has a splitting unit receiving and splitting metered fuel flow into out-going pilot and mains flows; pilot and mains fuel manifolds receiving the pilot and mains flows; and parallel mains flow scheduling valves distributing the mains flow. The mains flow scheduling valves pass the pilot fuel flow to injector pilot discharge orifices. Each mains flow scheduling valve has a chamber containing a piston, the chamber to a piston pilot side communicating with the pilot fuel manifold and the chamber to a mains side of the piston communicating with the mains fuel manifold. The piston is biased towards a closed pilot-only position preventing flow out of the chamber mains side to the injector mains discharge orifice. The piston is movable under increased pressure in the mains fuel manifold to an open pilot-and-mains position allowing flow out of the chamber mains side to the injector mains discharge orifice.

Abstract: An engine fuel control system includes a main pump which receives fuel from a low pressure source and delivers the fuel at a first high pressure, and a variable displacement augmenter pump which receives fuel from the low pressure source and delivers the fuel at a second high pressure. The augmenter pump has a servo-controller to vary its pump flow rate. The system includes an augmentation valve which is actuatable by an electrically operated control valve to open a flow path therethrough which diverts fuel delivered by the augmenter pump or to shut the flow path. The system includes a pressure drop control valve which senses a pressure differential between the second high pressure and a reference pressure, and controls the servo-controller to vary the pump flow rate of the augmenter pump. The pressure drop control valve spills some of the fuel delivered by the augmenter pump.

Abstract: A combustion staging system has a splitting unit receiving and splitting metered fuel flow into out-going pilot and mains flows; pilot and mains fuel manifolds receiving the pilot and mains flows; and parallel mains flow scheduling valves distributing the mains flow. The mains flow scheduling valves pass the pilot fuel flow to injector pilot discharge orifices. Each mains flow scheduling valve has a chamber containing a piston, the chamber to a piston pilot side communicating with the pilot fuel manifold and the chamber to a mains side of the piston communicating with the mains fuel manifold. The piston is biased towards a closed pilot-only position preventing flow out of the chamber mains side to the injector mains discharge orifice. The piston is movable under increased pressure in the mains fuel manifold to an open pilot-and-mains position allowing flow out of the chamber mains side to the injector mains discharge orifice.

Abstract: A fuel supply system for a gas turbine engine comprises a first positive displacement pump (16), a second positive displacement pump (27), said first and second positive displacement pumps (16, 27) being operable simultaneously for the supply of fuel from a low pressure source, and switching valve means (14) downstream of said first positive displacement pump (16) for changing a connection mode between said first and second positive displacement pumps (16, 27) between a series mode and a parallel mode.

Abstract: A method of operating a fuel system to determine the extent of internal wear of a fuel pump thereof comprises driving the fuel pump, moving a metering valve member to a closed position in which it bears against a resilient stop, increasing the operating speed of the fuel pump to increase the pressure applied to the metering valve member urging it towards the resilient stop to a point beyond which further movement of the metering valve member occurs, sensing when the further movement of the metering valve member occurs, and sensing the operating speed of the pump at the time when said further movement occurs.

Abstract: A metering valve arrangement comprises a spool 14 movable within a bore 12, the spool 14 and bore 12 together defining first and second control chambers 22, 32 the first control chamber 22 being supplied, in use, with fluid at a substantially fixed pressure, and a control valve arrangement 36 controlling the fluid pressure applied to the second control chamber 32, the control valve arrangement 36 comprising at least one solenoid operated three port valve 38, 56.

Abstract: A fuel system comprises a spill valve 38 operable to relieve the fuel pressure differential across at least one positive displacement pump 16, 18, a shut-off valve 32 operable to control the supply of fuel to an engine 84, and a two stage servo-valve 62 operable to control the operation of the shut-off valve 32, the spill valve 38 having a control chamber 40 the fluid pressure within which is controlled so as to be held at an intermediate level during engine shut-down.

Abstract: A pressure regulator comprises a housing, a metering spool movable within the housing to control the degree of opening of a metering orifice of the regulator, a first inlet through which hydraulic fluid at high pressure is supplied to said metering orifice, a first pressure chamber within the housing and containing hydraulic fluid at a reference pressure (Pref) to which one end of said metering spool is exposed, compression spring means within said first pressure chamber and acting at one end against said one end of said metering spool, an outlet from the housing downstream of said metering orifice, for hydraulic fluid at regulated pressure (Preg) from said metering orifice, a second pressure chamber containing hydraulic fluid at said regulated pressure Preg to which the opposite end of said metering spool is exposed, such that the metering position of the metering spool relative to the housing is a position of equilibrium between the force of the spring and Pref acting on one end of said metering spool and P

Abstract: An aircraft gas turbine engine fuel metering unit incorporating a memory device for storing data relevant to that unit, and an electrical connection arrangement whereby data can be read from and/or written to said memory device by an associated electronic engine controller, said stored data including data relating to at least one of the performance, the identification, the health, and the service life of that fuel metering unit. The invention further resides in an aircraft gas turbine engine fuel supply system and a method of operating such a system.