Abstract: An aircraft propulsion system comprises first and second thrust producing gas turbine engines. The system comprises a controller configured to determine a required overall propulsion system thrust level, and determine an engine core power level contribution from each aircraft gas turbine engine such that the overall propulsion system produces a minimum overall noise level and meets the required overall propulsion system thrust level. In meeting the minimum overall noise level, at least the first and second gas turbine engines are operated at different engine core power settings.

Abstract: An aircraft propulsion system comprises first and second thrust producing gas turbine engines. The system comprises a controller configured to determine a required overall propulsion system thrust level, and determine an engine core power level contribution from each aircraft gas turbine engine such that the overall propulsion system produces a minimum overall noise level and meets the required overall propulsion system thrust level. In meeting the minimum overall noise level, at least the first and second gas turbine engines are operated at different engine core power settings.

Abstract: An aircraft hybrid propulsion system (5) comprising an inboard gas turbine engine (10a, 10c) and an outboard gas turbine engine (10b, 10d), each comprising a propulsor (12a, 12b) and a respective electric machine (32a, 32b) coupled to one or more engine shaft (24a, 24b). An electrical interconnection (34) is provided between the electric machine (32a) of the inboard gas turbine engine (10a) and the electric machine (32b) of the outboard gas turbine engine (10b). A controller (36) is configured to transfer electrical power between the inboard gas turbine engine electrical machine and the outboard gas turbine engine electrical machine when a thrust setting change is selected.

Abstract: A propulsion system for an aircraft comprises at least first and second propulsors, each propulsor being independently driven by a respective electric motor. The first and second propulsors each comprise respective rotors comprising a plurality of blades. The rotor of the first propulsor (30a) comprises a different number of blades to the rotor of the second propulsor, and the rotors of the first and second propulsors each have a blade pitch varying mechanism.

Abstract: An inlet duct arrangement (40) comprises a duct (42) extending from an external fluid flow washed surface (50) into an interior region (51), the duct (42) having an opening (48) flush with the external surface (50). The arrangement (40) further comprises a hood (54) extending outwardly of the exterior surface (50) into external fluid flow (Y), and configured to direct external fluid into the duct (42). The hood (54) comprises an inlet aperture (56) configured to receive external fluid flow (Y), a first outlet aperture (62) configured to communicate with the duct (42), and a second outlet aperture (64). The second outlet aperture (64) is provided outwardly of the external surface (50) and downstream of the inlet aperture (56), and having a flow area smaller than the flow area of the inlet aperture (56).

Abstract: A pylon for attachment of a gas turbine engine to a wing of an aircraft has a trailing edge which is rearward of the trailing edge of the core fairing and the trailing edge of the fan nacelle. The pylon has two laterally-spaced side faces which extend in the rearward direction of the engine to end at the trailing edge of the pylon. Each side face has a bottom edge which extends in a rearward direction of the engine from the core fairing to the bottom end of the trailing edge of the pylon. The bottom edges merge such that the bottom edges form a single bottom edge. The pylon is intended to exert control on the bypass flow of a gas turbine engine. Other pylons are also provided which can also exert such control.

Abstract: The present invention relates to a flow discharge device (30) for discharging a flow of gas (F) from a first gaseous fluid (A) into a second gaseous fluid (B) which is of a lower pressure than the first gaseous fluid. The discharge device comprises a valve (34) disposed between the first and second gaseous fluids and arranged to regulate the discharge flow (F) and a swirler means (50) disposed between the valve (34) and the second gaseous fluid. The swirler means (50) comprises a plurality of radially extending circumferentially spaced vanes (61, 63, 65). In use the swirler means (50) swirls the discharge flow (F). This acts to reduce the energy, and therefore the pressure of the discharge flow. This results in quieter operation.

Abstract: A gas turbine engine has an annular bypass duct defined between a fan nacelle and a core fairing through which fan air is discharged. One or more bifurcator members are positioned inside the exit of the bypass duct to bifurcate the air flow in the bypass duct around the bifurcator members prior to exiting the bypass duct. The bifurcator members modify the flow field of the air in the bypass duct radially and/or tangentially with respect to the axis of the annular bypass duct.

Abstract: Noise generated by a gas turbine engine 6 supported by a pylon 8 on a wing 2 of an aircraft is reduced by influencing a shear layer generated between the free-stream flowfield and flow from the engine 6. The shear layer is influenced by means of one or more winglets 18, 20, 22 which interact with the free-stream flowfield to deflect the shear layer 14 downwardly, to avoid interaction with a flap 4 on the wing 2, or to reduce the strength of the shear layer 14.

Abstract: A bleed flow discharge device (136) adapted to discharge a bleed fluid flow into a main fluid flow, wherein the bleed flow discharge device comprises an outer wall (135) defining a passage (137) for the bleed fluid flow, the outer wall comprising a wave-shaped edge (139) where the bleed fluid flow meets the main fluid flow.

Abstract: An aircraft wing has an engine attachment position at which a gas turbine engine is attached beneath the wing, in use the engine ejecting a propulsive gas jet with a jet shear layer being formed between the gas jet and the surrounding air. The aircraft wing further has one or more elongate, flow-modifying formations protruding from the underside of the wing. The length direction of the or each formation is along the fore and aft direction of the wing with the trailing edge of the formation being rearward of the trailing edge of the wing. The flow-modifying formations can be arranged such that they interact with the jet shear layer to reduce noise generated by the interaction of the jet shear layer and the wing. They can also be arranged to block, attenuate and/or to scatter the noise reflected by the wing.

Abstract: Noise generated by a gas turbine engine 6 supported by a pylon 8 on a wing 2 of an aircraft is reduced by influencing a shear layer generated between the free-stream flowfield and flow from the engine 6. The shear layer is influenced by means of one or more winglets 18, 20, 22 which interact with the free-stream flowfield to deflect the shear layer 14 downwardly, to avoid interaction with a flap 4 on the wing 2, or to reduce the strength of the shear layer 14.

Abstract: A pylon is provided for attachment of a gas turbine engine to a wing of an aircraft. The gas turbine engine comprises a core fairing surrounding a core generator and defining a nozzle for discharging a core gas flow, and a fan nacelle surrounding the core fairing to define an annular bypass duct therebetween for discharging fan air. The pylon has a trailing edge which is rearward of the trailing edge of the core fairing and the trailing edge of the fan nacelle. The pylon further has having two laterally-spaced side faces which span the bypass duct between the fan nacelle and the core fairing and extend in the rearward direction of the engine to end at the trailing edge of the pylon. Each side face has a bottom edge which extends in a rearward direction of the engine from the core fairing to the bottom end of the trailing edge of the pylon.

Abstract: A gas turbine engine has an annular bypass duct defined between a fan nacelle and a core fairing through which fan air is discharged. One or more bifurcator members are positioned inside the exit of the bypass duct to bifurcate the air flow in the bypass duct around the bifurcator members prior to exiting the bypass duct. The bifurcator members modify the flow field of the air in the bypass duct radially and/or tangentially with respect to the axis of the annular bypass duct.

Abstract: The present invention relates to a flow discharge device (30) for discharging a flow of gas (F) from a first gaseous fluid (A) into a second gaseous fluid (B) which is of a lower pressure than the first gaseous fluid. The discharge device comprises a valve (34) disposed between the first and second gaseous fluids and arranged to regulate the discharge flow (F) and a swirler means (50) disposed between the valve (34) and the second gaseous fluid. The swirler means (50) comprises a plurality of radially extending circumferentially spaced vanes (61, 63, 65). In use the swirler means (50) swirls the discharge flow (F). This acts to reduce the energy, and therefore the pressure of the discharge flow. This results in quieter operation.

Abstract: In order to provide noise suppression, bumps or undulations are provided on a nozzle surface in order to vary the convergent-divergent ratio between that surface and an opposed nozzle surface. By such an approach, a circumferential variation in the shock cell pattern is created and the flow is deflected so as to enhance turbulent mixing thereby suppressing noise.

Abstract: In order to provide noise suppression, bumps or undulations are provided on a nozzle surface in order to vary the convergent-divergent ratio between that surface and an opposed nozzle surface. By such an approach, a circumferential variation in the shock cell pattern is created and the flow is deflected so as to enhance turbulent mixing thereby suppressing noise.