Abstract: A bearing arrangement comprising a shaft with a recess in its end, a bearing housing, an annular first bush comprising an inner first portion and an inner second portion and a second bush that engages the recess of the shaft. The first bush bears against the bearing housing. The shaft engages the inner first portion of the first bush. The second bush engages the inner second portion of the first bush.

Abstract: A gas turbine engine for an aircraft, comprising: an engine core; a covering configured to cover at least part of the engine core; and an engine accessory that interacts with the engine core or a component of the engine core; wherein the engine accessory is outside the covering.

Abstract: A method of operating a gas turbine engine compressor. The engine comprises a compressor having an environmental control system bleed port having an outlet in fluid communication with an aircraft environmental control system air duct, and an air turbine starter configured to rotate a compressor shaft of the gas turbine engine. The air turbine starter has an inlet in fluid communication with the environmental control system air duct via an air turbine valve. The method comprises determining a surge margin of the compressor, and where the surge margin of the compressor is determined to be below a predetermined minimum surge margin, opening the air turbine valve to supply air to the air turbine.

Abstract: A gas turbine engine comprising: an engine core comprising a compressor; a compressor bleed valve in communication with the compressor and configured to release bleed air from the compressor; at least one component provided at the inlet of the engine core having a de-icing conduit, configured to receive the bleed air; and a flow controller, configured to provide bleed air to the de-icing conduit of the at least one component in response to either or both of a requirement to de-ice the component and a requirement to release bleed air from the compressor to optimise operation of the core.

Abstract: A fluid ejector having: a diffuser duct for mixing of a first gas stream with a second gas stream having faster velocity than the first gas stream, wherein the diffuser duct extends along an axial direction; and wherein, in cross-section perpendicular to the axial direction, the diffuser duct is defined between a first wall extending around the axial direction, and a second wall extending around the axial direction, radially within the first wall.

Abstract: A hybrid aircraft propulsion system. The system comprises a gas turbine engine comprising a compressor, a combustor, one or more turbines, a shaft coupled to one of the turbines, and a bypass fan mechanically driven by the shaft. The system further comprises an electrical generator mechanically coupled to the shaft, and an auxiliary propulsor mechanically coupled to an electric motor and electrically coupled to the electric generator. At maximum power, the gas turbine engine is configured to produce a turbine entry temperature at maximum power between 1800 Kelvin and 2000 Kelvin, the engine comprises a fan bypass ratio of between 4:1 and 13:1, and the generator is configured to absorb between 10% and 60% of the mechanical power generated by the turbine.

Abstract: A gas turbine engine (10) comprising: an engine core (11), comprising a compressor (14, 15); an outer casing (25A) separating the engine core (11) from a bypass airflow; a compressor bleed valve (50) in communication with the compressor (14, 15) and configured to release bleed air from the compressor (14, 15); a bleed air duct (51) connected to the compressor bleed valve (50) and configured to eject the bleed air released by the compressor bleed valve (50) into an airflow at a location radially inward of the outer casing (25A).

Abstract: An electrical power generator system has: an input shaft for receiving a rotary input drive; plural output shafts connected by respective gear shifting arrangements to the input shaft thereby providing different gear ratios between the input shaft and each output shaft; and plural electrical generators powered by rotation of the respective output shafts, electrical power outputs of the generators being combined to supply a total power to a load. The input shaft operates over a range of rotation frequencies, and the gear shifting arrangements are configured to shift the gear ratios between the input shaft and the output shafts such that the output shafts operate over a narrower range of rotation frequencies.

Abstract: A bearing arrangement comprising a shaft with a recess in its end, a bearing housing, an annular first bush comprising an inner first portion and an inner second portion and a second bush that engages the recess of the shaft. The first bush bears against the bearing housing. The shaft engages the inner first portion of the first bush. The second bush engages the inner second portion of the first bush.

Abstract: An auxiliary oil supply apparatus for a rotating device (50, 51), the rotating device comprising a primary oil supply (52), a rotating component (50) and a static component (51) situated radially outwardly of a centre of rotation of the rotating component (50) and arranged to collect oil (58) held radially outwardly from the rotating component (50) as the rotating component rotates. The auxiliary oil apparatus comprises a scoop (56) associated with the rotating component (50) and is responsive to a change in a known parameter to move between a first position in the static component (51) to a second position between the static component (51) and the centre of rotation.

Abstract: The present disclosure concerns the detection of ice within a system. More specifically, but not exclusively, the disclosure concerns the detection of ice accretion within a gas turbine engine. The apparatus and method relies on heating a first region (38) of a component (44) and comparing the measured temperature of the first region (38) with a second temperature value, possibly measured at a distinct second region (40) of the component (44).

Abstract: A method of determining a faulty sensor of a sensor array of a gas turbine engine, the sensor array including at least first, second and third sensors, the method including the steps of: measuring a first set of sensor outputs prior to engine startup from each sensor, and calculating a first difference in the measured value for each sensor pair; after a period of time, measuring a second set of sensor outputs prior to engine startup from each sensor, and calculating a second difference in measured value for each sensor pair; calculating a further difference between the calculated first and second differences for each sensor pair; and identifying a failed sensor where two or more sensor pairs including a common sensor have a further difference above a predetermined threshold.

Abstract: A hydraulic seal arrangement including first and second rotatable components, the first defining a first annular trough defined by radially inwardly extending first and second walls, the second component defining a radially outwardly extending web between the walls. The first component includes a second trough defined by the second wall and a third wall axially spaced from the second, the second trough defining an open radially inner end defined by a radially inner end of the second wall such that the first and second annular troughs fluidly communicate around the circumference of the first component via the inner end of the second wall. At a first circumferential position, the second wall of the first component defines a second trough oil inlet providing further fluid communication between the first and second troughs and at a second circumferential position, the third wall of the first component defines a second trough oil outlet.

Abstract: A fluid transfer coupling comprises a first shaft assembly a second shaft assembly, and a seal assembly. The first shaft assembly comprises a first shaft and an annular fin attached to the first shaft, the annular fin having one or more internal passages extending therethrough. Each internal passage connects a centre portion of the first shaft to a radially outwardly facing side of the annular fin. The second shaft assembly comprises a second shaft and an annular trough extending radially outwardly of the second shaft.

Abstract: A method of determining a faulty sensor of a sensor array of a gas turbine engine (10), the sensor array comprising at least first, second and third sensors (A, B, C), the method comprising the steps of: a. measuring a first set of sensor outputs (S1A, S1B, S1C) prior to engine startup from each sensor (A, B, C), and calculating a first difference (S1A-S1B, S1A-S1C, S1B-S1C) in the measured value for each sensor pair (A; B, A;C, B;C); b. after a period of time, measuring a second set of sensor outputs (S2A, S2B, S2C) prior to engine startup from each sensor (A, B, C), and calculating a second difference (S2A-S2B, S2A-S2C, S2B-S2C) in measured value for each sensor pair (A;B, A;C, B;C); c. calculating a further difference ((S1A-S1B) -(S2A-S2B), (S1A-S1C)-(S2A-S2C), (S1B-S1C)-(S2B-S2C)) between the calculated first and second differences for each sensor pair (A; B, A;C, B;C); and d.

Abstract: A gas turbine engine accessory gearbox assembly has an accessory gearbox and a plurality of accessories arranged to be driven by the accessory gearbox. The accessory gearbox has a gear train and an accessory gearbox casing enclosing the gear train gears. Each accessory is driven by a drive shaft and the drive shafts of the accessories may be parallel. Each accessory has a first end and a second opposite end. Each accessory is secured at the first end to the accessory gearbox casing, a plurality of accessories are secured to a first side of the accessory gearbox casing and the second opposite end of at least two of the plurality of accessories are secured to a structural cross member. The structural cross member increases the stiffness and strength of the accessory gearbox assembly and allows the accessory gearbox casing to be reduced in thickness and reduces weight and cost.

Abstract: A valve monitoring apparatus has a system to determine a state of a valve. The system determines a fluid flow first pressure at a first location within a gas turbine engine, and a second pressure of a compressed fluid at a second location within the engine when the valve is in the first position; and compares the first and second pressures to determine the valve state. The system is arranged to command the valve to move from the first position towards a second position; determine the second pressure of the compressed fluid at the second location; compare the pressure at the second location when the valve is in the first position to the pressure at the second location when the valve has been commanded to move towards the second position; and, determine whether the valve has moved from the first position towards the second position when commanded to do so.

Abstract: A hydraulic seal arrangement including first and second rotatable components, the first defining a first annular trough defined by radially inwardly extending first and second walls, the second component defining a radially outwardly extending web between the walls. The first component includes a second trough defined by the second wall and a third wall axially spaced from the second, the second trough defining an open radially inner end defined by a radially inner end of the second wall such that the first and second annular troughs fluidly communicate around the circumference of the first component via the inner end of the second wall. At a first circumferential position, the second wall of the first component defines a second trough oil inlet providing further fluid communication between the first and second troughs and at a second circumferential position, the third wall of the first component defines a second trough oil outlet.

Abstract: A drive shaft assembly comprising a first shaft and a second shaft is disclosed. The second shaft is axially translatable from an engaged configuration with the first shaft at one limit of its travel to a disengaged configuration from the first shaft at the opposite limit of its travel. Engagement of the first and second shafts is via cooperating helical splines provided thereon. The helical splines give rise to a disengaging axial force on the second shaft in a fault condition in which a driving torque is applied from one of the first and second shafts to the helical splines in a rotational direction tending to unscrew the helical splines. Consequently when the second shaft is in the engaged configuration the disengaging axial force translates the second shaft to the disengaged configuration.

Abstract: A bearing cage for an anti-friction bearing includes a plurality of cage pockets with each cage pocket being adapted to accommodate a rolling element. Each of the cage pockets has a cylindrical profile with a corresponding cylindrical axis. The cage pockets are arranged in an alternating circumferential array of first cage pockets and second cage pockets, with the cylindrical axis of each first cage pocket intersecting with a rotational axis of the bearing cage on a first side of the bearing cage, and the cylindrical axis of each second cage pocket intersecting with the rotational axis of the bearing cage on a second opposite side of the bearing cage.