Abstract: A hydraulic seal arrangement for a rotating machine, particularly a gas turbine engine, comprises a hydraulic seal and a hydraulic trap. When the machine is shut down, oil is retained in the hydraulic trap. When the machine is restarted, the oil from the hydraulic trap is available to re-make the hydraulic seal, thereby reducing or avoiding the leakage that typically occurs in such seal arrangements until the flow of oil through the seal arrangement is re-established.

Abstract: A fan retention shaft is provided for retaining a fan within a gas turbine engine in the event of fan shaft failure. The fan retention shaft has a first shaft which in use extends from the engine and a second shaft to which in use the fan is attached, the second shaft being coaxial with the first shaft and the first and second shafts defining an annular passage between them. An energy absorbing medium is disposed within the annular passage. The fan retention shaft has a retaining formation for preventing the first shaft and the second shaft from moving axially with respect to one another. The retaining formation is configured to release the first shaft and the second shaft from their relative axial positions when a threshold axial load is applied to the fan retention shaft. The energy absorbing medium is arranged to absorb kinetic energy from the second shaft as the second shaft moves axially with respect to the first shaft.

Abstract: A gas turbine engine arrangement comprises a first gas turbine engine, a second gas turbine engine, a differential gearbox and an electrical generator. The differential gearbox has a first input drive, a second input drive and an output drive. The output drive of the differential gearbox is arranged to drive the electrical generator via an external, accessory, gearbox. The external, accessory, gearbox drives other accessories. The first gas turbine is arranged to drive the first input drive of the differential gearbox and the second gas turbine engine is arranged to drive the second input drive of the differential gearbox. The electrical generator and accessories are driven at a constant frequency speed/frequency.

Abstract: A propulsion engine (100) for an aircraft, the propulsion engine comprising: one or more fans (110, 120); driving means (132) arranged to drive the one or more fans; and power transfer means (134) connected to the one or more fans and arranged to selectively transfer a variable amount of power to or from the one or more fans so as to control the rotational speed of the one or more fans.

Abstract: A propulsion engine (100) for an aircraft, the propulsion engine comprising: one or more fans (110, 120); driving means (132) arranged to drive the one or more fans; and power transfer means (134) connected to the one or more fans and arranged to selectively transfer a variable amount of power to or from the one or more fans so as to control the rotational speed of the one or more fans.

Abstract: A fan retention shaft is provided for retaining a fan within a gas turbine engine in the event of fan shaft failure. The fan retention shaft has a first shaft which in use extends from the engine and a second shaft to which in use the fan is attached, the second shaft being coaxial with the first shaft and the first and second shafts defining an annular passage between them. An energy absorbing medium is disposed within the annular passage. The fan retention shaft has a retaining formation for preventing the first shaft and the second shaft from moving axially with respect to one another. The retaining formation is configured to release the first shaft and the second shaft from their relative axial positions when a threshold axial load is applied to the fan retention shaft. The energy absorbing medium is arranged to absorb kinetic energy from the second shaft as the second shaft moves axially with respect to the first shaft.

Abstract: A hydraulic seal arrangement for a rotating machine, particularly a gas turbine engine, comprises a hydraulic seal and a hydraulic trap. When the machine is shut down, oil is retained in the hydraulic trap. When the machine is restarted, the oil from the hydraulic trap is available to re-make the hydraulic seal, thereby reducing or avoiding the leakage that typically occurs in such seal arrangements until the flow of oil through the seal arrangement is re-established.

Abstract: A gas turbine engine arrangement (1) comprises a first gas turbine engine (10), a second gas turbine engine (70), a differential gearbox (57) and an electrical generator (112). The differential gearbox (57) has a first input drive (54), a second input drive (78) and an output drive (110). The output drive (110) of the differential gearbox (57) is arranged to drive the electrical generator (112) via an external, accessory, gearbox (56). The external, accessory, gearbox (56) drives other accessories (116, 120). The first gas turbine (10) is arranged to drive the first input drive (54) of the differential gearbox (57) and the second gas turbine engine (70) is arranged to drive the second input drive (78) of the differential gearbox (57). The electrical generator (112) and accessories (116, 120) are driven at a constant frequency speed/frequency.