Abstract: In a tandem fan gas turbine engine two fan compressor stages are provided connected by a flow duct housing a diverter valve which can be used to admit the flow from the first fan to the second fan or to divert it to exhaust through an auxiliary outlet in which case the second fan draws ambient air in through an auxiliary inlet. The connecting duct is annular in cross section because an inner cylindrical wall surrounds the shaft driving the front fan. The diverter valve which therefore has to operate in the annular duct comprises a pair of flat side lobes connected by curved plates which straddle the inner wall. The valve is operated by a rotary actuator in synchronism with closure means which obstruct or open the auxiliary outlet and inlet.

Abstract: A relight fuel flow schedule controls fuel flow to the combustor of a turbofan aeroengine during in-flight relight procedures. A first fuel ramp, whose slope decreases with increasing altitude, enables the combustor to light with minimum fuel flow for the altitude and thus helps to prevent overfueling. The fuel flow rate undergoes a step reduction, after detection of satisfactory combustion, to prevent compressor stall, but cannot drop below a predetermined level to guard against flameout. The first fuel ramp is repeated if satisfactory combustion does not occur. After a successive relight a second fuel ramp is varied from flat to positive slope depending on the ratio of the rate of change of high pressure compressor speed to a datum level in order to prevent a hung start and accelerate the engine until normal acceleration control laws takes over.

Abstract: In a gas turbine engine having a ceramic nozzle guide vane and a metal engine casing, a nozzle guide vane mounting comprises on the radially outermost end of the vane a circumferential flange extending at right angles to the long axis of the vane, a first spring means for applying a radially inward force to the radially outer surface of the flange, a second spring means for applying a radially outward force to the radially inner surface of the flange, and structural members of the engine casing to nip the first and second spring means between the structural members and the flange. The spring means may be C-ring seals made of a resilient material.

Abstract: A removable section of duct is sealingly coupled to a relatively fixed length of duct by means of a flexible, preferably elastic, sleeve which is attached to one of the lengths of duct towards one end thereof and at its other end to a relatively stiff collar which is shaped to fit closely over the adjacent end of the other duct. The elasticity of the sleeve tends to retain the collar in position and to maintain a tight seal while permitting a degree of relative movement including longitudinal thermal growth.

Abstract: In the manufacture of a wax pattern for use in the lost wax casting of a bladed rotor of the radial flow type, the bladed region of a master pattern is enclosed by a curable epoxy resin/aluminium powder composition. Sufficient of the cured resin composition is then machined away so that a plurality of resin composition segments are defined, one segment being interposed between adjacent blades on the master pattern. The segments are then removed from the master pattern and placed in an appropriately configured die member so as to define a complete die for the production of a wax pattern in the form of the master pattern.

Abstract: A fluid filter assembly comprises a heater and a filter in series fluid flow relationship. A means for bypassing a fluid around the heater and the filter is provided which comprises ducts and a relief valve interposed between them. In normal operation the relief valve is closed so all the fluid flows through the heater and the filter. The fluid and any liquid impurities entrained therein are heated by the heater prior to passing through the filter. At low temperatures the heater cannot normally provide sufficient heat to prevent solidification of the liquid impurities entrained within the fluid which block the filter. The relief valve then opens to allow a proportion of fluid to flow through the bypass so a reduced amount of fluid flows through the heater and the filter. The heater heats the reduced flow of fluid therethrough to a temperature sufficiently high to melt the solidified liquid impurities blocking the filter.

Abstract: A gas turbine engine fuel burner suitable for burning diesel fuel oil comprises an annular body and a center body coaxially located within the annular body so that an annular flow path is defined between them. At the upstream end of the burner an annular fuel manifold cooperates with the annular body and the center body to define two coaxial passages which direct air into the annular flow path with minimal turbulence. The low level of turbulence within the fuel burner reduces the possibility of spontaneous combustion occurring within the burner. The center body is hollow and is provided at its downstream end with an end cap which cooperates with the downstream end of the annular body to define a radial fuel/air mixture outlet.

Abstract: A program-controlled heat management system for an aircraft's bypass gas turbine (turbofan) engine installation, in which the engine's fuel system is put into direct heat exchange relationship with the engine's own oil system, and with an engine-driven electrical generators's oil system, by means of respective fuel/oil heat exchangers and also into selective indirect heat exchanger relationship with a variable proportion of the engine's bypass air means of an engine oil/air heat exchanger. The fuel system is switchable between four different fuel flow configurations in order to vary the heat flows between the fuel system and the oil systems, two of the fuel flow configurations also involving recirculation of fuel from the engine's fuel system to a fuel tank in the aircraft wing in order to put the fuel system into selective heat exchange relationship with the tank and hence with the airstream passing over the wing.

Abstract: An axial flow compressor with an inner casing and an outer casing. The inner casing has bleed apertures. The outer casing is provided with loading devices which are positioned adjacent to the bleed apertures such that the loading devices apply loads on the inner casing in the vicinity of the bleed apertures. Components of the loads applied by the loading devices are arranged to oppose and preferably balance any loads applied on the inner casing due to the bleed apertures' releasing the pressure differential across the inner casing. The loading devices comprise cylinders secured to the inner casing and pistons secured to the outer casing to form chambers. The chambers are supplied with fluid at a predetermined pressure. The loading devices oppose undesirable local reductions in clearance between static shrouds and the rotor blades.

Abstract: To evaulate the working line characteristics of a compressor of a gas turbine engine, fuel is supplied from the gas turbine engine fuel supply to a fuel accumulator via a control valve. The control valve is closed when a predetermined quantity of fuel is in the fuel accumulator, and a three way valve is adjusted to allow high pressure fluid from a fluid cylinder into the accumulator to pressurize the fuel. The fuel is then supplied from the accumulator via the valve to a combustion chamber to be burnt to increase the pressure in the combustion chamber and hence the compressor. The pressure of the fuel supplied which causes a surge is indicative of the working line characteristics of the compressor. The pressure and quantity of fuel supplied are varied until a surge is produced.Reworking of compressors with reduced surge margin can be carried out. Enables evaluation to take place while the engine is fixed to an aircraft.

Abstract: The vanes of a radial turbine have pressure surfaces which are convex when viewed in a plane normal to the axis of rotation of the radial flow rotor and suction surfaces which are concave when viewed in the same plane. The curvature acts to promote favorable radial surface pressure gradients to assist the control of boundary layer migration in the intervane passages and also increase the structural integrity of the vane members. The otherwise flexible extremities of the vane members are stiffened by introducing the curvature, as the natural resonant vibration frequencies of the vanes are changed. The invention is also applicable to the vane members of a radial or mixed flow impeller in gas or other fluid applications.

Abstract: In a gas turbine firtree root tooth structure in which a firtree root is retained in a shaped slot in a turbine rotor disc by virtue of teeth cooperating with notches in the slot, the bearing surface of a root tooth is barrelled against a planar surface of the respective notch so as to give point contact against that surface, whereby, under load, the barrelled surface crushes so as to override pitch tolerances and even out load distribution. If the barrelling is located at or in the vicinity of the tooth face center, the tendency of the tooth to crack under repeated loadings is minimized.

Abstract: A turbofan gas turbine engine (10) comprises a fan rotor (32) driven by a core engine (11) via a shaft (36) and a reduction gear (38). A lubricant source (63) is arranged to supply lubricant to the reduction gear (38) to lubricate gear teeth and bearings (52) in the reduction gear (38). An annular collector (76) is positioned coaxially around the reduction gear (38) and is secured to the fan rotor (32) and is driven by the reduction gear (38). The annular collector (76) is arranged to collect lubricant leaving the reduction gear (38) on its inner surface. A number of static scoops (82) collect lubricant from adjacent the inner surface of the annular collector (76) to return the lubricant to valves (86). The valves (86) allow the lubricant to return to the lubricant source (63) in normal operation.

Abstract: For processing data relating to the performance of an apparatus, the data is analyzed using a Kalman Filter. After a first pass of data through the filter, the results are refined by discarding at least one less significant component performance change and/or sensor bias. The Kalman Filter is then re-run using the modified data. As further runs of the Kalman Filter are performed, as required, the input of each successive run is refined by discarding from the preceding run at least one further component performance change and/or sensor bias. For each run, an objective function is evaluated for the amount of unexplained measurement change and/or the amount of component performance change and sensor bias. The run whose results show an acceptable value for the objective function is selected as the best solution. In this way, the tendency of the Kalman Filter to distribute the cause of any sensed performance change over all the possible sources of that change is avoided.

Abstract: A differential gear assembly which is suitable for providing a power off-take from a gas turbine engine, comprises first and second power input gears which drive a plurality of idler gears rotatably mounted on a common cage structure. The idler gears are grouped in meshing pairs so that one idler gear of each pair is additionally in meshing engagement with one of the power input gears and the other idler gear of each pair is additionally in meshing engagement with the other of the power input gears. Together the first and second power input gears drive the common cage structure at the mean speed of the power input gears and the common cage structure in turn drives a single power output shaft.

Abstract: A bladed rotor (19) suitable for a gas turbine engine (10) comprises a plurality of aerofoil blades (21) mounted on the periphery of a disc (20). Each of the aerofoil blades (21) has a root part (25) which locates in the disc (20) and is constituted by two radially extending circumferentially spaced apart root portions (26,27). The circumferentially outward flanks of the root portions (26,27) are configured to define a fir-tree type blade fixing which locates in a correspondingly shaped recess (34) in the disc (20). The root part (25) configuration provides weight reduction in the rim region of the disc (20), thereby reducing stresses within the disc (20).

Abstract: A valve for an extraction device of a molten metal or molten alloy atomizing chamber comprises a valve member which is rotatably mounted in a pipe. The peripheral edge of the valve member has a groove in which is located a rubber seal. A protecting member is located in the pipe upstream of the valve member with respect to the flow of an atomizing gas and metal particles through the pipe. The protecting member is positioned such that when the valve member is in the open position the protecting member is immediately upstream of the peripheral edge of the valve member to prevent metal particles impinging upon and wearing the rubber seal. The protecting member is also supplied with cooling gas and is arranged to direct the cooling gas through passages over the surfaces of the valve member to prevent the seal overheating.

Abstract: An engine for application to the propulsion of aerospace vehicles (terrestrial or orbital) capable of operating in two propulsive modes. The first mode employs liquid hydrogen to pre-cool the intake air of a turbo-compressor in order to deliver it at high pressure to a rocket type combustor/nozzle assembly. In this mode the external atmosphere is the source of oxidizer for the fuel. At a high Mach number in the hypersonic regime the engine changes to the second mode which is a conventional high performance rocket engine using liquid oxygen carried on the vehicle to oxidize the liquid hydrogen fuel. Both modes of propulsion use common hardware, namely the liquid hydrogen pump and the combustor nozzle assembly.

Abstract: The invention relates to a method and apparatus for testing the response of a stress wave sensor to check that the transducer and amplifier are working satisfactorily.A pulse generator is connected to the stress wave sensor at a point between the transducer and the amplifier. The pulse generator supplies an electrical pulse to the stress wave sensor. A pulse cancelling device prevents the electrical pulse going directly to the amplifier. The electrical pulse causes the transducer to emit stress wave energy into a structure to which the transducer is acoustically coupled. The transducer detects the stress wave propagating in the structure and supplies an electrical signal to the amplifier. The electrical signal is amplified by the amplifier and demodulated by demodulator. A processor measures the peak and area of the demodulated amplified electrical signal and comares them with stored values.

Abstract: An alloy mix suitable for the repair of nickel-based alloy components is disclosed. The alloy mix contains a mixture of two alloy powders. The constituents of the first powder, in percentages by weight are:______________________________________ Al 2-3 Co 9-11 Cr 8-10 Fe 0-1.8 Hf 1.0-1.5 Ta 1.-1.5 Ti 1.25-1.75 W 6-8 B 2.8-3.4 Y 0.001-0.02 Ni Remainder ______________________________________and the constituents of the second powder, in percentages by weight, are: ______________________________________ C .13-.17 Al 5.25-5.75 B 0.01-0.02 Co 9.0-11.0 Cr 8-10 Hf 1.3-1.7 Ta 2.25-2.75 Ti 1.25-1.75 W 9.5-10.5 Zr 0.03-0.