Abstract: A fuel system comprises a first, variable displacement fuel pump operable to supply fuel through a metering valve to an engine, a control servo operable to control the operation of the first pump, a pressure drop control valve (PDCV) responsive to a pressure drop across the metering valve, a second fuel pump, and a spill valve movable between an open position in which substantially all of the fuel supplied by the second fuel pump is returned to an inlet side thereof, and a closed position, or partially closed position, wherein a proportion of the fuel supplied by the second pump is delivered to the engine.

Abstract: A rotatable rectifier arrangement comprises a rectifier component 14a, 14b electrically connected to a bus bar 16, 18 the bus bar 16, 18 being provided with at least one fan blade formation 30.

Abstract: A fuel control system for reheat burners of a gas turbine engine has a plurality of metering valves for respective burners, and throttle valves in series with the respective metering valves. A pressure regulating valve is provided for introducing pressurized fuel into fuel manifolds downstream of the respective throttle valves when the metering and throttle valves are shut. The pressure regulating valve also acts to relieve pressure in low pressure parts of the system when the latter is closed down and to prevent excessive temperature rise at the inlet of a fuel supply pump. The metering valves include pressure return ports which communicate with the metering valve outlets when those valves are shut.

Abstract: A system comprises a pressure raising valve having a valve member movable within a bore between a closed position and an open position in which fuel supplied to the pressure raising valve from a metering valve, in use, is delivered to an engine manifold, the valve member being urged towards its closed position by the fuel pressure within a control chamber, the pressure raising valve including a low pressure port which communicates with the control chamber when the valve member is in its closed position, the valve member closing the low pressure port upon movement thereof away from its closed position beyond a predetermined distance.

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 method and apparatus are provided in which control data for a generator system is multiplexed onto a synchronization signal.

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 generator controller for controlling a permanent magnet generator where each phase of the generator is connectable to a DC link via electrically controllable switches, the controller characterised by a data processor adapted to receive a measurement of generator current output and a demand current, and to form a current error between the demanded value and the measured generator current; derive a target voltage as a function of the current error; and form control signals for the electrically controllable switches as a function of the target voltage.

Abstract: A disconnect mechanism is provided which, upon a suitable trigger event, such as excess temperature causes a camming element 40 having a tapered head 52 to move under the urging of a compression spring 60 such that the tapered head 52 becomes trapped between a rotating element 32 and a support 42. This gives rise to frictional inter-engagement which prevents further rotation of the rotating element 32 and thereby locks the rotating machine against further rotation. This is turn causes the shear region to fail thereby drivingly disconnecting the machine from its prime mover.

Abstract: A fuel supply system for a gas turbine engine including first and second positive displacement pumps operated simultaneously to supply fuel under pressure from a low pressure source, a combining spill valve controlling the output flows from the first and second pumps to combine the outputs of the first and second pumps for supply to a metering valve of the system, or to spill some or all of the output of one or both pumps back to the low pressure supply, a pressure raising and shut off valve arrangement downstream of the metering valve for isolating the fuel system from an associated engine until the fuel pressure upstream of the pressure raising and shut off valve arrangement exceeds a predetermined pressure, and, a control system dependent upon the position of the combining spill valve for reducing said predetermined pressure at which said pressure raising and shut off valve arrangement opens.

Abstract: A drive disconnect device is provided in which a drive transfer element (12) is axially movable with respect to input and output shafts (2, 14) so as to selectively disconnect them. A collar (50) is disposed in spaced apart configuration around the drive transfer element so that they do not touch except when the disconnect device is operated to disconnect the drive. When the disconnect operation is initiated, force is provided from a resilient element (56) to move the drive transfer element.

Abstract: A pressure regulator includes a housing, a metering spool, a first pressure chamber at a reference pressure to which one end of the metering spool is exposed, a spring within the first pressure chamber acting against the one end of the metering spool, a second pressure chamber containing hydraulic fluid at the regulated pressure acting against the opposite end of the metering spool, wherein the position of the metering spool relative to the housing is a position of equilibrium that changes to maintain a predetermined pressure difference between the reference pressure and the regulated pressure. An abutment against which the opposite end of the spring reacts is provided and a third pressure chamber at a control pressure acts on the abutment, such that the control pressure can be changed to adjust the position of the abutment to change the pre-load of the spring to adjust the value the predetermined pressure difference.

Abstract: An AC to DC converter with harmonic suppression is provided. The harmonic suppression is provided by forcing an instantaneous current conflict between series connected rectifier bridges 54, 80, such that a voltage waveform at 6 times the AC supply frequency of the AC supply is automatically generated. This waveform is then injected via a injection circuit to give harmonic cancellation.

Abstract: A fuel control system for a staged combustion engine comprising, a fuel metering unit including a fuel metering valve having a fuel metering orifice the opening of which is varied to meter the flow of fuel through the metering valve in use, a fuel staging unit receiving fuel from the metering valve of the fuel metering unit and incorporating a staging valve for dividing the flow of fuel from the fuel metering unit to pilot burner and main burner output lines, a connection between a fuel pressure region of said fuel metering unit and a port of said staging valve, and, overthrust detection means causing said staging valve, in response to overthrust detection, to connect said port of said staging valve to low pressure, whereby to drain fuel under pressure from said pressure zone of said fuel metering unit to low pressure to limit or reduce the fuel supplied from the fuel metering unit to the fuel staging unit and thus to the engine in use.

Abstract: A generator controller (4) is provided which is able to detect and respond to failure of a generator output voltage sensor, whilst being able to distinguish voltage sensor failure from output voltage collapse due to the presence of an overload or short circuit condition. The presence of a voltage sensor failure is indicated by the measured output voltage being below a first voltage threshold whilst the output current is also below a current threshold.

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 compensation circuit is provided for use in a drive arrangement for an isolation transformer in series with a capacitor. The compensation circuit applies a compensation voltage to the capacitor such that the voltage across the capacitor remains substantially invariant.

Abstract: An unpressurised aeronautical generator (2), is provided which includes a two stage oil pump (6) comprising a centrifugal pump (8) and a gerotor pump (26). The centrifugal punp draws oil through openings (18) in a manifold, pressurises it and supplies it to the gerotor pump. The gerotor pump then pumps the pressurised oil throughout the generator. A small gerotor pump is used, which is still sufficient to operate at low pressures and high altitudes.

Abstract: A rotor assembly for a dynamo electric machine, the rotor assembly comprising a rotor core incorporating radially extending rotor poles, rotor windings encircling respective rotor poles, circumferentially extending pole tips at the outer end of each pole respectively, said tips overlying the rotor winding encircling the respective pole, a plurality of rotor slot closure members, each closure member spanning the gap between a pair of adjacent poles, and including lateral flanges interposed between the respective rotor windings and the associated pole tips, a spacer member positioned beneath each closure member and engaging the radially extending faces of the adjacent windings, and, a locking wedge assembly comprising a pair of locking wedges extending axially of the rotor assembly between each closure member and the associated spacer, the locking wedges extending with their tapers in opposite directions so that moving the wedges longitudinally towards one another increases the radial dimension of the combinati

Abstract: An AC to DC converter with harmonic suppression is provided. The harmonic suppression is provided by forcing an instantaneous current conflict between series connected rectifier bridges 54, 80, such that a voltage waveform at 6 times the AC supply frequency of the AC supply is automatically generated. This waveform is then injected via a injection circuit to give harmonic cancellation.