Abstract: A machine having a plurality of sub-assemblies, having a geometric computational model is generated for the machine, including the sub-assemblies and one or more module of machine readable code defining how vibration is communicated through said geometric model. First and second instances of the computational model are run to generate outputs of loading throughout the machine geometry as a result of the vibration of the geometric model under a simulated machine operating condition. The first and second instances respectively includes the computational model with and without inclusion of vibration induced by a control system for one or more sub-assembly of the machine. A maximum loading threshold is determined for the machine. A threshold for one or more control parameter in the control system is set based on the contribution of the vibration induced by the control system to the maximum loading threshold.

Abstract: A fuel spray nozzle including a primary atomizer to discharge a flow of swirled atomised fuel along and around a fuel spray nozzle axis. The primary atomiser includes outer air swirler disposed radially outwardly of a fuel pre-filmer channel. A secondary atomiser disposed around the primary atomiser includes secondary inner air swirler to swirl flow along an inner air channel. The secondary inner air swirler disposed radially inwardly of a secondary fuel pre-filmer channel of the secondary atomiser. A primary outer air channel defined between the primary outer swirler and the secondary inner swirler. The secondary inner air swirler include splitter wall to separate swirling flow in the secondary inner channel from the primary flow of atomised fuel. The secondary inner air swirler includes primary cap wall integral with and extending radially inwardly from the splitter wall to direct flow from the primary outer channel inwardly towards the fuel spray.

Abstract: A procedure for repairing a polymer matrix composite component is provided. The procedure includes the steps of: providing a polymer matrix composite component having a site prepared for repair by removal of damaged or defective material; locating an uncured, polymer matrix composite repair patch at the site to re-build the component thereat; and curing the polymer matrix of the repair patch by heating the patch using eddy currents induced by one or more alternating current coils. The repair patch is without metallic additives, such that the repaired polymer matrix composite after the curing step is also without metallic additives in the vicinity of the repair patch.

Abstract: There is provided a gas turbine engine comprising a low pressure shaft and a high pressure shaft; wherein the low pressure shaft connects a fan to a fan drive turbine, and the high pressure shaft connects a high pressure turbine to a compressor section. The low pressure shaft and the high pressure shaft are arranged such that when operating at idle the idle shaft speed ratio is greater than 6.05. The idle shaft speed ratio is the ratio of the speed of the high pressure shaft to the speed of the low pressure shaft at idle conditions.

Abstract: A combustion chamber comprising a plurality of circumferentially arranged cassette segments coupled to a combustor head at one end and a wall section at the other end, each cassette segment extending the full length of the combustion chamber, and wherein the combustor head has an annular tongue structure on a mating surface, the tongue structure engages with a groove portion present in each of the cassettes so that when assembled the groove portions in the each of the plurality of cassette segments forms a substantially continuous groove.

Abstract: An oil tank filling system for filling the oil tank of a gas turbine engine that includes an aft core cowl. The system includes an oil tank that has an oil tank top and an oil tank bottom and is located within a core of the engine, an oil access port located on the aft core cowl, and an oil tank filling pipe that leads from the oil access port to a tank filling port located at or adjacent the oil tank bottom. The system is configured so that oil that is supplied to the oil access port flows to and into the oil tank using gravitational force. A method of filling the oil tank of a gas turbine engine and a gas turbine engine that includes the oil tank filling system.

Abstract: A turbofan gas turbine engine having a bypass duct, and a bypass airflow measurement system. The bypass airflow measurement system comprises: at least one acoustic transmitter configured to transmit an acoustic waveform across the bypass duct of the gas turbine engine though which a bypass airflow passes to at least one acoustic receiver; where the at least one acoustic transmitter and the at least one acoustic receiver are located on an axial plane that is substantially perpendicular to the bypass flow. A method of measuring bypass airflow properties of a turbofan gas turbine engine is also described.

Abstract: A system and a method of measuring grain orientations of a metal component. The method includes defining a series of measurement locations on the metal component at which to take a series of measurements indicative of grain orientations at corresponding measurement locations. The method further includes defining a nominal grain orientation at each measurement location. The method further includes loading the measurement locations into a computer-controllable fixture suitable for positioning the metal component. The method further includes locating the metal component in the computer-controllable fixture. The method further includes taking the series of measurements at the series of measurement locations. The method further includes analysing the measurement at each measurement location relative to the nominal grain orientation at the corresponding measurement location.

Abstract: An aircraft engine comprising a fan, the fan having a diameter D and including a plurality of fan blades, the fan blades having a sweep metric S, each fan blade having a leading edge, and a forward-most portion on the leading edge of each fan blade being in a first reference plane. The aircraft engine further comprises a nacelle, comprising an intake portion forward of the fan, a forward edge on the intake portion being in a second reference plane, wherein the intake portion has a length L measured along an axis of the aircraft engine between the first reference plane and the second reference plane, the aircraft engine having a cruise design point condition Mrel, wherein Mrel is between 0.4 and 0.93, and L/D is between 0.2 and 0.45.

Abstract: A gas turbine engine for an aircraft including: an engine core including a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan including a plurality of fan blades; a gearbox that can receive an input from the core shaft, and can output drive to a fan shaft via an output of the gearbox so as to drive the fan at a lower rotational speed than the core shaft; and a fan shaft mounting structure arranged to mount the fan shaft within the engine, the fan shaft mounting structure including at least two supporting bearings connected to the fan shaft. A fan-gearbox axial distance is defined as the axial distance between the output of the gearbox and the fan axial centreline, the fan-gearbox axial distance being greater than or equal to 0.35 m.

Abstract: A method of manufacturing a component is provided. The method includes performing a machining operation by moving a rotating, abrasive grinding tool along a feed direction to remove material from the component. At least the part of the component from which the material is removed is formed of composite material. The abrasive grinding tool follows a trochoidal path along the feed direction.

Abstract: Electrical systems for connecting rotary electric machines to dc networks operating at different voltages V and W where V>W are provided, along with gas turbine engine arrangements incorporating such systems.

Abstract: An engine core including a turbine, compressor, and core shaft connecting the turbine and compressor, the turbine being the lowest pressure turbine, the core shaft having a running speed range from 1500-6200 rpm, and the compressor being the lowest pressure compressor; a fan located upstream of the engine core; and a gearbox receiving an input from the core shaft and outputs drive to the fan. The engine core further includes three bearings arranged to support the core shaft, the three bearings including a forward bearing and two rearward bearings, the core shaft having a length between the forward and the rearmost rearward bearing ranging from 1800-2900 mm, and a minor span between two rearward bearings ranging from 250-350 mm, wherein there is no primary resonance of the core shaft between the forward and forwardmost rearward bearing within the running speed range of the core shaft.

Abstract: A gas turbine engine for an aircraft comprises a high-pressure (HP) spool comprising an HP compressor and a first electric machine driven by an HP turbine; a low-pressure (LP) spool comprising an LP compressor and a second electric machine driven by an LP turbine; a combustor; an electrical energy storage unit; and an engine controller configured to: in response to receipt of a request for an increased electrical power supply by the engine (dPD) within a requested timeframe (dt), evaluating a current HP compressor surge margin (dRH/RH) and a current LP compressor surge margin (dRL/RL) based on the operating points thereof; in response to evaluating that one or more of the HP compressor and the LP compressor has insufficient surge margin to facilitate a change of electrical power supply at a requested rate (dPD/dt), meeting the requested electrical power demand using the electrical energy storage unit whilst increasing fuel flow to the combustor to accelerate the engine.

Abstract: A gas turbine engine comprises carbon fibre fan blades. At cruise conditions, the fan tip air angle ? in the range: 64 degrees???67 degrees. Additionally or alternatively, the fan blade tip angle ? is in the range of from 62 to 69 degrees. Arrangements in accordance with the present disclosure provide advantages which may include improved bird-strike performance. This may allow advantages associated with carbon fibre fan blades to be better exploited.

Abstract: A gas turbine engine includes an engine core including a compressor, a combustor, and a turbine, the compressor being connected to the turbines through a respective shaft; and a cabin blower system comprising: an electric variator comprising a first electrical machine connected to a first shaft arranged along a first axis, a second electrical machine connected to a second shaft arranged along a second axis, and a power management system; a cabin blower comprising a compressor driven by a third shaft arranged along a third axis, the compressor comprising an air inlet and an air outlet; and a differential gearbox. The gas turbine engine further includes an accessory gearbox arranged within an accessory gearbox casing and adapted to drive the cabin blower system.

Abstract: A composite storage tank comprises a composite wall enclosing a gas storage volume and defining a cylindrical portion (406) of the tank. The composite wall incorporates first) and second sets of metallic fibres each of which is susceptible to embrittlement by hydrogen and has ends extending through the exterior surface of the composite wall. By measuring the electrical resistances of the metallic fibres, a measure of the amount of hydrogen that has leaked through the composite wall over a period of time, and the present physical condition of the tank, may be determined. The approximate axial and azimuthal coordinates of a particular leakage point may also be determined.

Abstract: A gas turbine engine having a reverse travelling wave first flap mode, Fan RTW, and including a fan located upstream of the engine core; a fan shaft; a front engine structure arranged to support the fan shaft and having a front engine structure nodding mode including a pair of modes at similar, but not equal, natural frequencies in orthogonal directions; and a gearbox. An LP rotor system including the fan system and a gearbox output shaft arranged to drive the fan shaft first reverse and first forward whirl rotor dynamic modes, Rotor RW, and 1FW. The engine has a maximum take-off speed, MTO.

Abstract: A composite gas storage tank includes a composite wall defining a main storage volume and a hollow conduit portion communicating with and extending away from the main storage volume. A hollow coupling element has a length portion which is partially embedded within and extends substantially parallel to the hollow conduit portion of the composite wall. The hollow conduit portion and the coupling element provide communication between the main storage volume and the tank exterior. A leakage path around the hollow coupling element is significantly longer than those of tanks of the prior art and reduces the rate at which hydrogen leaks from the tank. A carbon fibre filament winding extends over the length of the hollow conduit portion and provides a radially inwardly-directed force biasing the carbon fibre material of the hollow conduit portion into contact with the coupling element, further reducing the leakage rate on the leakage path.

Abstract: The present disclosure relates to a fan blade for a gas turbine engine, the fan blade comprising an aerofoil portion having a leading edge extending from a root to a tip, the radial distance between the leading edge at the root and the leading edge at the tip defining a blade span. A maximum thickness of the cross-sections through the aerofoil portion from a suction surface of the aerofoil portion to a pressure surface of the aerofoil portion perpendicular to the camber line decreases along the blade span from the root to the tip. There is a discontinuity in the rate of decrease of maximum thickness between a radius at 30% of the blade span from the aerofoil root and 70% of the blade span from the aerofoil root. The rate of decrease of the maximum thickness before the discontinuity is less than the rate of decrease of the maximum thickness after the discontinuity.