Abstract: Provided is a method of operating a gas turbine engine. The engine includes a combustor having a plurality of fuel spray nozzles and a fuel system arranged to provide fuel to the combustor. The system includes: fuel pump; fuel distributing valve downstream of the pump arranged to distribute fuel to the plurality of nozzles and bias fuel flow to the nozzles such that a first subset of the plurality of nozzles receives more fuel than a second subset of the plurality of nozzles; and fuel-oil heat exchanger. The method includes providing a fuel to the combustor and transferring heat from oil to the fuel in the fuel-oil heat exchanger before the fuel enters the combustor so as to lower a viscosity of the fuel to 0.58 mm2/s or lower on entry to the combustor at cruise conditions. Also provided is a gas turbine engine for an aircraft.

Abstract: There is provided an electrical machine comprising: a rotor at least partially disposed within a rotor chamber; a stator core coaxially arranged with the rotor chamber; and a stator sleeve. The stator sleeve is annular and is positioned between the stator core and the rotor chamber. The stator sleeve comprises a magnetic material having a relative permeability of at least and an intrinsic coercivity no greater than 1 kAm?1.

Abstract: A method of operating a gas turbine engine having a lean burn staged combustion system having a combustor in which fuel is combusted. The gas turbine engine includes a fuel-oil heat exchanger arranged to transfer heat between oil and fuel that is provided to the combustor. The method includes transferring heat from the oil to the fuel before the fuel enters the combustor so as to raise the fuel temperature to an average of at least 135° C. on entry to the combustor at cruise conditions. Also provided is a gas turbine for an aircraft.

Abstract: A method of operating a gas turbine engine including an engine core including: a turbine, compressor, combustor, core shaft; fan; fan shaft; gearbox that receives input from the core shaft and outputs drive to the fan via the fan shaft; primary oil loop system that supplies oil to the gearbox; and heat exchange system, which includes an air-oil heat exchanger through which oil in the primary oil loop system flows; and a fuel-oil heat exchanger through which the oil and fuel flow so heat is transferred therebetween, wherein the system branches so oil flows along each branch and the exchangers are arranged in parallel on different branches of the system; and a modulation valve that allows the oil sent via each branch to be varied. The method includes controlling the heat exchange system to raise the fuel temperature to at least 135° C. on entry to the combustor at cruise conditions.

Abstract: A combustor arrangement includes a fuel injector, and a seal arranged around the fuel injector and having an upstream end and a downstream end. The seal includes an annular body at least partially abutting the fuel injector. The annular body includes an inner surface facing the fuel injector and an outer surface radially spaced apart from the inner surface relative to the central axis. The annular body further includes a plurality of slots disposed on the inner surface and circumferentially spaced apart from each other relative to the central axis. Each slot axially extends at least partially from the downstream end to the upstream end. Each slot is disposed in fluid contact with the fuel injector. The seal also includes a flange radially extending from the outer surface of the annular body at the upstream end.

Abstract: A method of operating a gas turbine engine including a combustor. The combustor includes a combustion chamber and a plurality of fuel spray nozzles configured to inject fuel into the chamber. The nozzles include a first and second subset of fuel spray nozzles. The combustor is operable in a condition wherein the first subset is supplied with more fuel than the second. A ratio of the number of nozzles in the first subset to the second is 1:2 to 1:5. The method includes operating the engine so a reduction of 20-80% in an average of particles/kg of nvPM in the exhaust when the engine is operating at 85% available thrust for given operating conditions and when the engine is operating at 30% is obtained when fuel provided to the nozzles is a sustainable aviation fuel instead of a fossil-based hydrocarbon fuel. Also, a gas turbine engine for an aircraft.

Abstract: An auxiliary power unit (10) for an aircraft (1) comprises a gas turbine engine comprising an engine core (12). The engine core comprises a core compressor (14) and core turbine (18) coupled by a core shaft (24). The auxiliary power unit further comprises a load spool comprising a load compressor (30), a load turbine (20) and a permanent magnet electric machine (28), each being coupled by a load shaft (26). The load shaft (26) and core shaft (24) are configured to rotate independently of one another.

Abstract: Reconfigurable permanent magnet electrical machines and aircraft power and propulsion systems comprising such electrical machines are described. In one aspect, an aircraft power and propulsion system comprises: a gas turbine engine; a permanent magnet electrical machine comprising a rotor drivingly coupled to a spool of the gas turbine engine, and a stator comprising windings controllably switchable between a star configuration and a delta configuration; a DC electrical network; an AC:DC power electronics converter, an AC side of which is connected to terminals of the stator windings of the electrical machine and a DC side of which is connected to the DC electrical network; and a control system. The control system is configured to monitor at least one operating condition of the power and propulsion system and to control the switching of the stator windings between the star configuration and the delta configuration based on the at least one operating condition.

Abstract: A method of quantifying the quality of a scan image of at least a portion of an object against a background, the method including: deriving a first measure of contrast and a first measure of sharpness from a first region of the scan image, and a second measure of contrast and a second measure of sharpness from a second region of the scan image; and determining a quality index value indicative of the quality of the scan image based on the first measure of contrast, the first measure of sharpness, the second measure of contrast and the second measure of sharpness.

Abstract: Gearboxes for aircraft gas turbine engines, in particular to arrangements for journal bearings such gearboxes, and to related methods of operating such gearboxes and gas turbine engines. Example embodiments include a gearbox for an aircraft gas turbine engine, the gearbox including: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin.

Abstract: There is disclosed a method of identifying non-conformance of a manufactured component, the method comprising: performing a volumetric scan to generate a 3-dimensional (3D) image of a volume of space containing the component, the 3D image comprising a plurality of voxels, each voxel representing a sub-volume within the volume of space and assigned a voxel value relating to properties of the material in the sub-volume; generating a component histogram giving the frequency of each voxel value within the volume of space; and comparing the component histogram to a template histogram, and identifying differences between the component histogram and the template histogram, and based on the comparison, determining whether there is a defect in the component.

Abstract: A thermal management system for a gas turbine engine includes a plurality of inlet and outlet vanes extending from a bypass inner wall towards an outer cowl, a plurality of first removable shims, a plurality of second removable shims, and a third removable shim. Each first removable shim extends between and engages the outer cowl and a corresponding inlet vane. Each second removable shim extends between and engages the outer cowl and a corresponding outlet vane. The third removable shim extends between and engages a heat exchanger and the outer cowl. Each of the plurality of first removable shims, each of the plurality of second removable shims, and the third removable shim is removable for positionally adjusting the outer cowl relative to the bypass inner wall.

Abstract: The present disclosure provides a method of scanning a component by computed tomography, the method comprising: providing the component having a first density; supporting the component in a scanning orientation using a support bed, the support bed comprising a granular material disposed in a container, the granular material having a second density lower than the first density; wherein supporting the component comprises at least partially embedding the component in the granular material. The method further comprises scanning the component in the scanning orientation by X-ray or gamma ray scanning to produce an image of the component.

Abstract: A computer-implemented method of determining a value of a reliability parameter of an electrical machine, the method includes: estimating an operating temperature of at least a part of the electrical machine based on a measure of a current drawn or supplied by the electrical machine; and determining the value of the reliability parameter based on the estimated operating temperature.

Abstract: A method of manufacturing a CMC component includes performing a plurality of manufacturing stages. Each manufacturing stage includes layering a ply on a mandrel if a current manufacturing stage is a first manufacturing stage; layering a ply on the CMC component formed in a preceding manufacturing stage if the current manufacturing stage is subsequent to the first manufacturing stage; determining an intermediate weight of the CMC component after layering the ply in the current manufacturing stage; determining a first weight difference between the intermediate weight of the CMC component and a target weight corresponding to the current manufacturing stage; determining a second weight difference between the first weight difference and the corresponding weight of remaining parts; selecting a part from the remaining parts for which the second weight difference is minimum; and disposing the selected part on the ply layered in the current manufacturing stage.

Abstract: Disclosed is an aircraft accessory drive system comprising: a drive shaft configured to provide a drive input; a critical accessory directly coupled to the drive shaft so as to be directly driven by the drive shaft; a parasitic drive system configured to transmit drive input from the drive shaft to one or more less critical accessories, wherein the parasitic drive system comprises a torque limiter configured to decouple the parasitic drive system from the drive shaft and the critical accessory in response to a jam affecting the parasitic drive system or one or more of the less critical accessories. Also disclosed are a gas turbine engine comprising an aircraft accessory drive system, and an aircraft comprising an aircraft accessory drive system.

Abstract: A gas turbine engine includes a support structure for attaching the engine to an aircraft pylon. The support structure includes: an engine-side interface member, a pylon-side interface member interfacing to the engine-side interface member, and a top V-shaped connection formation above the engine core and pair of side V-shaped connection formations on opposite lateral sides of the engine core, each V-shaped connection formation being formed by a pair of connection members meeting at a vertex, the vertex of the top V-shaped connection formation joining to the top of the engine-side interface member, the vertices of the side V-shaped connection formations respectively joining to the bottom ends of the engine-side interface member, and the connection members extending forwardly from their respective vertices to join to front fixation points at the core casing.

Abstract: A method for determining a location of an object relative to a component includes providing a frame. The method further includes coupling a plurality of encoders to the frame. The plurality of encoders is configured to generate a plurality of encoder signals. Each encoder signal from the plurality of encoder signals is representative of a location of the object relative to the respective encoder. The method further includes removably attaching the frame to the component. The method further includes receiving the plurality of encoder signals from the plurality of encoders. The method further includes determining a location of the object relative to the component based on the plurality of encoder signals.

Abstract: A repair system for repairing a surface of a workpiece includes a first tool configured to rotate in a first direction. The first tool contacts the surface of the workpiece during the rotation of the first tool in order to repair the surface of the workpiece. The repair system further includes a second tool configured to rotate in a second direction opposite to the first direction. The second tool contacts the surface of the workpiece during the rotation of the second tool in order to repair the surface of the workpiece. The repair system further includes a drive mechanism coupled to each of the first tool and the second tool.

Abstract: A method of monitoring health of a power semiconductor device includes: determining a steady state loading of the power semiconductor device; when it is determined that the power semiconductor device is under a steady state loading, monitoring a case temperature parameter relating to a temperature of the case of the power semiconductor device over a predetermined period, derive a normalised parameter from the monitored case temperature parameter and determine the health of the power semiconductor device based on the normalised parameter.