Abstract: Gearboxes for aircraft gas turbine engines, in particular arrangements for journal bearings such gearboxes, and related methods of operating such gearboxes and gas turbine engines, including 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: A laser ablation tool including, a pulsed laser source, a prism that rotates in a plane perpendicular to light from the laser source, and a mirror that is moveable in at least one direction and which is set at an angle relative to the light from the laser source.

Abstract: A laser ablation tool comprising a laser source which produces a beam heaving a beam path and an ablation head, the ablation head comprising a housing which on each side of the beam path is separated into a first and second portion, and at least a first Risley prism and a second Risley prism connected to the first and second portions of the housing the first and second Risley prisms being connected to a rotation mechanism, so that the two Risley prisms can be moved relative to each other and the housing so as to deflect the beam.

Abstract: A computer implemented method of modelling the degradation of at least a component within an abrasive environment, the method comprising: obtaining a 3D scan of a surface of a component, processing the surface images of the component, determining the surface properties, inputting the data into a trained prediction model, predicting the performance of the component, and simulating the surface evolution over time or use of the component.

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 Z-pin for increasing a delamination resistance of continuous fibre-reinforced polymer composites, formed of a composite material including a polymer matrix, and a plurality of fibres embedded in the polymer matrix and aligned along the length direction of Z-pin, the fibres having an elongation at break of at least 2% and a tensile strength of at least 5 GPa, the polymer matrix having an elongation at break equal to or greater than the elongation at break of the fibres, and a tensile strength of at least 120 MPa.

Abstract: A resin composition that is useful in the preparation of protective coatings. The resin composition comprises a polyfunctional cyanate ester, a phenol-end-modified PDMS oligomer, and a catalyst.

Abstract: A shaft component, which in particular can be connected or is connected to the input or output side of a gear box in a gas turbine engine, in particular an aircraft engine, wherein the shaft component has at least two regions comprising fiber reinforced plastic, with fibers in the at least two regions differing in their composition, their geometric properties, their density, their radial position, their axial position and/or in their fiber orientation in the shaft component.

Abstract: A gas turbine engine has a compression system blade ratio defined as the ratio of the height of a fan blade to the height of the most downstream compressor blade in the range of from 45 to 95. 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: A hydrogen-fuelled aircraft power system incorporates a gas turbine engine and a fuel cell, in which air supply and cooling of the fuel cell is integrated with the gas turbine engine to improve overall efficiency of the power system. The system may be part of a turbofan, turboprop or electric propulsion system for an aircraft.

Abstract: An electrical power system including: an electrical power source, a power electronics converter, an electrical network, a current limiting diode and a controllable circuit interruption device, wherein: the current limiting diode is configured to limit a fault current passing between the electrical power source and the electrical network in a fault condition; and the controllable circuit interruption device is configured to interrupt the fault current in response to a determination that the electrical power system is in the fault condition.

Abstract: A gas delivery system intended for use in delivering hydrogen gas from a cryogenic liquid hydrogen storage tank is provided. The gas delivery system has: a cryogenic liquid storage tank; an evaporator; a pressurisable gas reservoir; a valve sub-system including: a multi-outlet valve arrangement having a first valve inlet, a first valve outlet and a second valve outlet; and a multi-inlet valve arrangement having a second valve inlet, a third valve inlet and a third valve outlet; a delivery line connected to the third valve outlet; an evaporator feed line connecting the storage tank and the evaporator inlet; an evaporator dispensing line connecting the evaporator and the first valve inlet; a reservoir feed line connecting the first valve outlet and the reservoir; a reservoir dispensing line connecting the reservoir and the second valve inlet; and a reservoir bypass line connecting the second valve outlet and the third valve inlet.

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 hydrogen-fuelled gas turbine engine has a fuel input path from a fuel input of the engine to a combustor, the engine further comprising a heat-exchanger located in the fuel input path and a fuel turbine located in the fuel input path between the heat-exchanger and the combustor. The heat-exchanger is arranged to receive waste heat from the engine core in order to heat hydrogen fuel introduced at the fuel input prior to input thereof to the combustor. The engine further comprises an air compressor arranged to be driven by the fuel turbine. The engine provides for most of the waste heat of combustion to be recovered and used without the need for heavy electrical or mechanical apparatus and is therefore particularly advantageous in aeronautical applications.

Abstract: A method of forming a protective coating includes providing a substrate including a major surface. The method further includes providing a top coat layer adjacent to the major surface of the substrate. The top coat layer includes a top coat surface distal to the substrate. The method further includes forming a plurality of slots in the top coat layer. The method further includes at least partially heating the top coat surface above a threshold temperature, such that a first portion of the top coat layer extending from the top coat surface partially melts to form a glazed layer, and a second portion of the top coat layer disposed between the glazed layer and the major surface of the substrate is not melted and includes at least a portion of each of the plurality of slots.

Abstract: An aircraft includes a machine body that encloses a turbofan gas turbine engine and a plurality of ancillary systems. The turbofan gas turbine engine includes, in axial flow sequence, a first heat exchanger module, a fan assembly, a compressor module, a combustor module, a turbine module, and an exhaust module. The aircraft includes a second heat exchanger module. The machine body comprises a single fluid inlet aperture, with the fluid inlet aperture being configured to allow a fluid cooling flow to enter the machine body and to pass through the first heat exchanger module. When a temperature of the fluid cooling flow is less than a temperature of a fluid to be cooled, the fluid to be cooled is directed to the first heat exchanger module, and when a temperature of the fluid cooling flow is greater than a temperature of the fluid to be cooled, the fluid to be cooled is directed to the second heat exchanger module and cooled using a fuel supply for the gas turbine engine.

Abstract: Electrical power systems for distributing electrical power in arrangements including one or more gas turbine engines; one such system includes: one or more rotary electric machines, coupled to a gas turbine engine spool; converter circuits connected to the rotary electric machines converting between alternating current (ac) and direct current (dc), wherein the rotary electric machines and the converter circuits output a number R?2 of dc power channels, each channel having an index r=(1, . . . , R); and a group of N dc load channels connected to the R dc power channels by a switching arrangement, wherein each dc load channel has an index n=(1, . . . , N) and R<N?2R.

Abstract: A direct injection fuel system is shown for injecting hydrogen fuel into a gas turbine combustor. The fuel injection system includes a plurality of fuel injector blocks. Each fuel injector block includes a fuel admission duct having an inlet for receiving hydrogen fuel from a fuel supply, an outlet for delivering hydrogen fuel into the combustor and a central axis extending from said inlet to said outlet. Each fuel injector block also includes an air admission duct located around the periphery of the fuel admission duct, having an inlet for receiving air from a diffuser and an outlet for delivering air into the combustor for mixing with the hydrogen fuel.

Abstract: There is disclosed a method of inserting a reinforcing rod into a hole in a laminated material. The method comprises a feed operation in which a feed clamp clamps a rod whilst moving towards the laminated material to feed an end section of the rod through a guide clamp into a hole in the laminated material. The method further comprises a re-supply operation in which the feed clamp releases the rod and moves relative the rod along a return direction away from the laminated material whilst the guide clamp clamps the rod. A corresponding insertion head for inserting a reinforcing rod, and insertion equipment comprising the insertion head and a controller is also disclosed.

Abstract: In some examples, an article may include a substrate and a coating system on the substrate. The coating system may include a layer comprising a plurality of voids, wherein respective voids of the plurality of voids define respective void volumes; and a nucleating agent within at least some of the respective void volumes of the layer, wherein the nucleating agent is configured to induce crystallization of the molten CMAS. The coating system may include an environmental barrier coating, thermal barrier coating, and/or abradable coating.