Abstract: A variable pitch propeller module includes first and second multi-bladed propellers arranged to be driven in opposite rotational directions by a reduction gear mechanism, via shafts. First and second drums are rotatably mounted on the hubs of the first and second propellers and the drums are arranged to rotate the blades of the propellers. A hydraulic motor is mounted coaxially on and rotates with the second propeller, the hydraulic motor being arranged to drive the drums by via a pitch change gear assembly. A hydraulic fluid feed tube extends coaxially through the reduction gear mechanism and both propellers to supply hydraulic fluid to the hydraulic motor. An annular sleeve is positioned coaxially on the tube. The hydraulic fluid feed tube has passages and the sleeve has passages which are aligned to allow hydraulic fluid to flow to the hydraulic motor to vary the pitch of both blades. The feed tube and sleeve are moved axially to control the flow of hydraulic fluid to the hydraulic motor.

Abstract: A reheat system for a gas turbine engine includes a plurality of radial flameholders constructed of non-metallic material, such as a ceramic composite or carbon/carbon reinforced material, mounted on a metallic support structure in the engine jet pipe. The metallic support structure may be cooled by air from the engine bypass duct, and the non-metallic flameholders are capable of withstanding higher exhaust gas temperatures in the jet exhaust beyond the capability of currently used metal alloy materials. However, the mounting assembly must be capable of absorbing the considerable differential thermal expansion which will take place.

Abstract: A fire-proof seal for a tubular conduit (16) of thermally conductive material adapted to contain an elongate member (24) extending axially outside the conduit, the seal comprising a thermally conductive sleeve (34) surrounding the member externally of the conduit and in thermal contact with an external flange (40) of the conduit, and a thermally fusible material (30) surrounding the member within the conduit, whereby, in the event of a fire in the vicinity of the member externally of the conduit, heat is transmitted through the sleeve into the conduit so as to fuse the thermally fusible material and block the interior of the conduit.

Abstract: A distance sensor is arranged to be moveable relative to a workpiece, during a machining operation this movement having a limit at a position where a finished workpiece would be within an accurate measuring range of the sensor. As machining progresses the sensor is moved towards the workpiece, stopping either when the separation of sensor and workpiece reaches a pre-set value of when the sensor reaches the limit of its movement. If the separation of sensor and workpiece reaches the pre-set value the sensor is moved away from the workpiece and then towards it again, repeating the cycle. If the sensor reaches the limit of its movement it remains in this position and measures its separation from the workpiece for the remainder of the machining operation.

Abstract: An air intake suitable for an aerospace propulsor comprises a duct which contains, in flow series, a first heat exchanger, a water separator, and a cryogen injector and a second heat exchanger. Air entering the intake is cooled by the first heat exchanger to cause the majority of the water vapor in the air to condense into water droplet form. The water droplets are then removed by the air flow by the water separator. The cryogenic injector reduces the air flow temperatures still further so that any remaining water in the air flow is converted to small dry ice crystals which do not block the second heat exchanger.

Abstract: A radially inwardly extending annular flange (47) is integral with an annular portion (26) of an outer shaft (23). The annular flange (47) forms an oil weir in operation. A radially outwardly extending annular sealing member (56) is mounted on an annular portion (48,50) of an inner shaft (39). The shafts (23,39) are arranged to rotate relative to each other. The outer diameter of the sealing member (56) is greater than the inner diameter of the annular flange (47). In order to introduce or remove the sealing member (56) from the hydraulic seal, past the annular flange (47), the sealing member (56) is axially split by a circumferentially extending spiral to define axially overlapping portions (56A,56B). The sealing member (56) is parted axially to form a clearance and a portion of the annular flange (47) is located in the clearance. The sealing member (56) is rotated about its axis when the slope of the spiral is parallel to the annular flange (47 ).

Abstract: In the pursuit of the forming of light composite materials which may be substituted for metal without loss of strength, composites have been manufactured from silicon carbide fibers in a titanium matrix. Titanium diffuses into the given boundaries of the silicon carbide and degrades it. Yttria has been sandwiched between the titanium and silicon carbide, to provide a reaction skin of yttria which reduces the extent of diffusion. The present invention oxidizes the silicon carbide prior to applying the yttrium and thus further improves the resistance to diffusion.

Abstract: An aerospace propulsor is powered by liquid hydrogen. The hydrogen is passed through a turbine which drives a liquid oxygen pump. During non-atmospheric flight, the liquid oxygen is directed to the propulsor's combustion chamber where it is mixed with the liquid hydrogen and combustion takes place. However during atmospheric flight, the liquid oxygen is pumped to drive a turbine which powers a fan adapted to provide additional pressurization of air entering the engine for combustion.

Abstract: In a gas turbine engine power unit the gas turbine engine is provided with combustion chambers whose axes are perpendicular to the engine longitudinal axis. Each combustion chamber is located within and supported by a corresponding tubular member. Each tubular member is supported from a first annular manifold and in turn supports a second annular manifold which is located wholly within the first manifold. The first manifold receives air from the gas turbine engine compressor and directs it to a regenerative heat exchanger. Heated air returned from the regenerative heat exchanger is directed to the second manifold from where it flows through apertures in the tubular members to the combustion chambers. The manner in which the manifolds and combustion chambers are mounted reduces stresses arising from thermal gradients.

Abstract: An air intake suitable for an aerospace propulsor comprises a duct in which are provided two pirmary heat exchangers arranged in parallel relationship and a secondary heat exchanger downstream of the primary heat exchangers. The primary and secondary heat exchangers are arranged to place a cryogenic fluid in heat exchange relationship with the air flow through the duct. Icing of the primary heat exchangers is controlled by interrupting the flow of cryogenic fluid to each of the primary heat exchanger in turn. Thus while one heat exchanger is subject to ice accretion hereon, the temperature of the other increases sufficiently for de-icing thereof to occur.

Abstract: A control system actively controls at least one troublesome mode of an unsteady motion phenomenon in turbomachinery in order to enable an increase in the operating range of the turbomachinery. For example, rotor blade flutter or rotating stall may be controlled in a turbocompressor. The control system has a control bandwidth which is at least partly coextensive with the bandwidth of the unsteady motion phenomenon and operates by passing sensor signals related to the unstady motion phenomenon from a sensor array in the turbomachine to a mode filter which produces a signal or signals which are related to the troublesome mode or modes. The selected mode signals are amplified and phase-shifted by time-variable amounts so as to produce control signals having controlled amplitude and phase relationship to the troublesome mode.

Abstract: In the laser drilling of gas turbine engine blades there is provided a method of maintaining constant the distance between a laser nozzle and the surface to be drilled by measuring the topography of the surface and using that data to control the focusing of the laser beam onto the surface. The topography is measured by determining the back pressure of a stream of oxygen blown through the nozzle onto the surface, and relating the back pressure to the distance between the nozzle and the surface. The distance measured is used to control a servo operated table so as to move the surface to the optimum distance from the nozzle.

Abstract: A gas turbine engine fuel control system comprises a microprocessor based control unit programmed to calculate the total fuel requirement to achieve a demanded engine speed on the basis of a steady state fuel requirement plus an additional overfuelling requirement. The overfuelling element is calculated in accordance with the lowest of a number of limiting variables which ensure continued engine integrity and safety and a minimum level to prevent engine flame-out and in which all variables and datums are related to an equivalent engine speed or rate of change of engine speed. The steady state fuel element is likewise calculated using a theoretical engine model based on engine acceleration characteristics. The overall system confers highly accurate control of engine speed and acceleration and enables the use of a simple fuel metering valve, in which fuel flow is directly proportional to valve position.

Abstract: A device (26) for sealing an inspection aperture in a casing (28) of a gas turbine engine (10) comprises a hollow housing (36) and a sealing plate (54). The housing (36) has an inspection aperture (40A) and a sealing ball (42). The sealing ball (42) moves along an arcuate track (45) formed on the housing (36) between a first position in which the sealing ball (42) seals against a conical seat (44) around the aperture (40A) and a second position in which the sealing ball (42) is displaced radially from the axis (52) of the inspection aperture (40A) to allow a borescope to be inserted therethrough.Normally the sealing plate (54), which has a cylindrical member (58), is arranged so that the cylindrical member (58) fits coaxially within and seals the aperture (40A). The sealing plate (54) is normally secured to the housing (36).

Abstract: A breather outlet for the gearbox of an aircraft mounted gas turbine engine comprises an aerodynamic mast which extends from the engine nacelle. The mast contains a breather duct which interconnects the interior of the gearbox with an exhaust outlet. The exhaust outlet is generally rearwardly facing and is spaced apart from the engine nacelle so as to avoid oil staining of the nacelle.

Abstract: The stress-wave activity produced by the interaction between a writing instrument and a surface during the generation of a given piece of handwriting on the surface is detected and stored. The stress-wave activity produced by a subsequent generation of the given piece of handwriting is then compared with that produced by the initial piece of handwriting in order to determine whether the initial and subsequent handwriting pieces have a common author.

Abstract: A failure tolerant engine mounting is formed by three links between the engine and its support structure, one of the links being arranged so that in the event of failure of either of the other links it will form a connection between three points on the engine and supporting structure which are symmetrically arranged about a vertical axis through the engines center of gravity.

Abstract: In a gas turbine engine having a ceramic nozzle guide vane supported by a metal turbine casing the radially outer end of the vane is provided with opposed frustoconical sections which converge towards each other onto a middle cylindrical section. A metal split ring surrounds the cylindrical section, and the radially inner and outer ends of the ring abut the frustoconical sections. The split ring is provided with a flange which cooperates with a groove structure on the turbine casing, thus enclosing the split ring to the casing. A bolt means fastens together two sections of the casing either side of the vane, thereby holding the split ring against the vane. On increase in temperature the split ring expands more than does the vane. The ends of the split ring therefore slide against the frustoconical surfaces of the vane to take up the expansion, and in so doing maintain contact with the vane.

Abstract: The throttle fuel flow of an aircraft jet engine is controlled by measuring the actual value of an engine parameter demand and measuring the error between the actual value and a value of the parameter demand calculated from a number of engine operating data. The error is then used to drive an integrating fuel throttle value until the error is substantially zero. The engine parameter chosen is the high pressure compressor delivery mach number.

Abstract: The normally multi-part gas turbine engine labyrinth seal outer portion which carries an abradable lining, is formed from a single piece and has a groove machined in its periphery for the receipt of the feet of respective stator vanes. Pins are fitted in pairs through the walls of the groove to provide lateral location for the feet. The pins and a groove liner are made from an anti-frettage material.