Abstract: This invention concerns an aircraft propulsion system in which an engine has an engine core comprising a compressor, a combustor and a turbine driven by a flow of combustion products of the combustor. At least one propulsive fan generates a mass flow of air to propel the aircraft. An electrical energy store is provided on board the aircraft. At least one electric motor is arranged to drive the propulsive fan and the engine core compressor. A controller controls the at least one electric motor to mitigate the creation of a contrail caused by the engine combustion products by altering the ratio of the mass flow of air by the propulsive fan to the flow of combustion products of the combustor. The at least one electric motor is controlled so as to selectively drive both the propulsive fan and engine core compressor.

Abstract: A gas turbine engine for an aircraft configured with an engine core that has a turbine, a compressor, and a core shaft connecting the turbine to the compressor. A fan located upstream of the engine core, that has a plurality of fan blades. A gearbox arranged to receive an input from the core shaft and to output to the fan so as to drive the fan at a lower rotational speed than the core shaft. The gearbox being an epicyclic gearbox having a sun gear, a plurality of planet gears, a ring gear, and a planet carrier on which the planet gears are mounted. The gearbox having an overall gear mesh stiffness, and wherein the overall gear mesh stiffness of the gearbox is greater than or equal to 1.05×109 N/m and less than or equal to 8.0×109 N/m.

Abstract: A gas turbine engine for an aircraft includes an engine core having a core length and comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor, the turbine comprising a lowest pressure rotor stage, the turbine having a turbine diameter at the lowest pressure rotor stage; and a fan located upstream of the engine core, the fan comprising a plurality of fan blades extending from a hub, the hub and fan blades together defining a fan face having a fan face area and a fan tip radius, wherein a ratio of the fan tip radius to the turbine diameter at the lowest pressure rotor stage is in a range from 1.2 to 2.0; and wherein the engine core length is in a range from 150 cm to 320 cm.

Abstract: The present disclosure concerns an oil distribution assembly for a system having rotating components requiring a supply of oil, such as bearing components of a gas turbine engine. Example embodiments include an oil distribution assembly for a gas turbine engine, comprising: an oil distributor mounted for rotation about a rotation axis of the assembly and comprising an internal volume having a plurality of channels extending along an inner radial surface of the oil distributor; and an oil injector arranged to direct a supply of oil to the plurality of channels in a direction having a component in a first direction along the rotation axis; wherein each of the plurality of channels is angled relative to the rotation axis such that a radial distance between each channel and the rotation axis increases along the rotation axis.

Abstract: An electric machine (212) comprises a turbomachine rotor (203) having a hub (302) and an axis of rotation (A-A) about which the turbomachine rotor is arranged to rotate. The turbomachine rotor includes a plurality of blades (301). Each blade has a root (303) attached to the hub, a tip (304) remote from the hub, a leading edge (305) and a trailing edge (306), a pressure side and a suction side (307). A stator (502) is located circumferentially around the turbomachine rotor. Each blade further comprises a rotor element at the tip comprising a permanent magnet having a first pole (401) and a second pole (402), the first pole being located adjacent the suction side of the blade and the second pole being located adjacent the pressure side such that a magnetic flux path extends perpendicularly through the blade tip.

Abstract: Fault-tolerant four-phase electric drive systems are provided. One such system comprises: a rotary electric machine having a permanent magnet rotor and an alternate-wound stator having eight evenly-spaced coils arranged in pairs, each coil in each pair being separated by 180 degrees; a first phase (?A) comprising a first one of the coil pairs and a first phase drive circuit connected therewith; a second phase (?B) separated by +45 degrees from the first phase and comprising a second one of the coil pairs and a second phase drive circuit connected therewith; a third phase (?C) separated by +90 degrees from the first phase and comprising a third one of the coil pairs and a third phase drive circuit connected therewith; a fourth phase (?D) separated by +135 degrees from the first phase and comprising a fourth one of the coil pairs and a fourth phase drive circuit connected therewith; and a controller connected with the first, second, third and fourth phase drive circuits to control operation thereof.

Abstract: Gas turbine engines and methods of starting gas turbine engines, the gas turbine engine including: an electronic engine controller; one or more spools designated a starting spool for starting the engine, and has a required starting torque ?s; a permanent magnet alternator mechanically coupled with the starting spool, the alternator, in a motor mode, provides a peak torque of ?a, and, in a generator mode, generates electrical power for the electronic engine controller; and an electrical starter-generator mechanically coupled with the starting spool. The starter-generator in a motor mode, provides a peak torque of ?sg, and, in a generator mode, generates electrical power for an external load. ?sg+?a??s and ?sg, ?a<?s, and the electronic engine controller, during a start procedure, operates both the permanent magnet alternator and the starter-generator in a motor mode to drive the starting spool.

Abstract: A gas turbine engine for an aircraft has an engine core including a turbine, a compressor, and a core shaft connecting the turbine to the compressor, the turbine being the lowest pressure turbine of the engine and the compressor being the lowest pressure compressor of the engine; a fan located upstream of the engine core; and a gearbox that receives an input from the core shaft and outputs drive to the fan. The engine core further has three bearings arranged to support the core shaft, and two rearward bearings, and wherein the forward most rearward bearing has a bearing stiffness defined by the radial displacement caused by the application of a radial force at the axial centerpoint of the bearing, and wherein a stiffness ratio of the bearing stiffness at the forward most rearward bearing to the minor span is in the range from 0.08 to 0.5 kN/mm2.

Abstract: A fan blade comprising a tip surface configured in use to face an internal wall of a nacelle. The tip surface having a suction side edge, a pressure side edge and a chamfer such that in use the suction side edge is further than the pressure side edge from the internal wall of the nacelle. The chamfer angle of the chamfer varies along the tip surface between a leading edge of the fan blade and a trailing edge of the fan blade.

Abstract: A gas turbine engine comprising: a compressor; a first turbine; and a first compressor bleed valve in fluid communication with the compressor and configured to release bleed air from the compressor; wherein the first compressor bleed valve is configured to release bleed air to a downstream location in the engine, the downstream location being downstream of the first turbine; wherein the first compressor bleed valve is configured to open wherein the first compressor bleed valve is configured to open to at least two positions, to thereby release a variable amount of bleed air from the compressor.

Abstract: An axial flow turbomachine (102) for producing thrust to propel an aircraft is shown. The turbomachine has an inner duct (202) and an outer duct (204), both of which are annular and concentric with one another. An inner fan (206) is located in the inner duct, and is configured to produce a primary pressurised flow (P). An outer fan (207) is located in an outer duct, and is configured to produce a secondary pressurised flow (S). The outer fan has a hollow hub (208) through which the inner duct passes. A hub-tip ratio of the outer fan is from 1.6 to 2.2 times a hub-tip ratio of the inner fan.

Abstract: A system, method and machine-readable instructions for monitoring a power electronics device. The system involves a semiconductor device, at least one sensor and a processor. The processor is configured to monitor a junction temperature of the semiconductor device by determining from the at least one sensor an on-state resistance of the semiconductor device and calculating the junction temperature of the semiconductor device according to a relationship between the on-state resistance of the semiconductor device and the junction temperature of the semiconductor device. The processor may apply an ageing coefficient to the on-state resistance.

Abstract: A gas turbine engine for an aircraft. The gas turbine engine for an aircraft comprising: an engine core comprising an annular gas passage, a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and a power gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft. The engine further has a recirculatory lubricant system which feeds lubricant to and scavenges lubricant from the power gearbox. The engine further has a circumferential row of inlet guide vanes, located downstream of the fan at an air inlet of the annular gas passage. The recirculatory lubricant system includes one or more return passages for lubricant scavenged from the power gearbox, the return passages crossing the annular gas passage through one or more of the inlet guide vanes.

Abstract: A gas turbine engine has a compression system radius ratio defined as the ratio of the radius of the tip of a fan blade to the radius of the tip of the most downstream compressor blade in the range of from 5 to 9. This results in an optimum balance between installation benefits, operability, maintenance requirements and engine efficiency when the gas turbine engine is installed on an aircraft.

Abstract: An electric machine including a stator having a fully non-magnetic core and stator windings formed of a non-superconducting transposed conductor to reduce eddy current losses. It further includes a rotor having a fully non-magnetic core and superconducting windings or superconducting magnets which produce a magnetic field for interaction with the stator windings. A cryogenic cooling system is arranged to cool the stator windings to reduce conduction losses in the stator windings.

Abstract: A control system operable includes a modified primary control parameter for an aircraft, the control system includes: a primary control parameter leg configured to output a demand in an aircraft primary control parameter; a primary control parameter compensation leg configured to receive a change in absolute levels and/or spatial distributions of swirl angle and/or fan pressure at a primary control parameter relative to a reference and convert the change into the primary control parameter; a processor adapted to receive the demand in the primary control parameter output from the primary control parameter leg and the change to the primary control parameter output from the primary control parameter compensation leg; compare the demand in the primary control parameter output from the primary control parameter leg and the change to the primary control parameter output from the primary control parameter compensation leg; and generate a modified primary control parameter for the aircraft.

Abstract: An aircraft gas turbine engine includes a main engine shaft, a main engine shaft bearing arrangement for rotatably supporting the main engine shaft, and an electric machine including a rotor and a stator. The rotor is mounted to the main engine shaft and is rotatably supported by a further electric machine bearing arrangement extending between the rotor and the stator, and the stator is mounted to static structure of the gas turbine engine.

Abstract: A method of calibrating a gas turbine engine having a propulsive fan, and an engine core, the method including: measuring a total thrust generated by the engine; measuring the thrust generated by the engine core; measuring first and second engine performance parameters; based on the total thrust and engine core thrust, determining a thrust generated by the propulsive fan; providing a first power setting parameter associating the fan thrust with the first engine performance parameter; and providing a second power setting parameter associating the engine core thrust with the second engine performance parameter.

Abstract: A combustor for a gas turbine engine comprising: a combustion chamber; at least one fuel spray nozzle operable to deliver a fuel-air mixture into the combustion chamber, wherein during operation of the gas turbine engine the fuel-air mixture is combusted in the combustion chamber, thereby producing a combustion flame; a microwave generator coupled to a waveguide arranged to guide microwaves from the microwave generator into the combustion chamber such that the microwaves are incident on at least a portion of the combustion flame; and a detector operable to detect at least a portion of the microwaves reflected by the combustion flame and/or atomised fuel droplets.

Abstract: There is described a fixture for supporting a plurality of gas turbine engine blades that are to be imaged. The mobile fixture comprises a plurality of interconnected mounts arranged to lie within a common plane, wherein each mount comprises at least one support surface for holding a respective blade. Support surfaces of respective mounts are oriented such that their respective normal vectors have the same angle with respect to the common plane.