Abstract: A variable area nozzle for a gas turbine engine is provided that has a circumferential outer boundary (which may be formed at least in part by the nacelle of a turbofan engine) that has a fixed portion and a movable portion. The movable portion is movable by an actuator both upstream and downstream from a datum position. This allows the exit area of the variable area nozzle to be adjusted according to flight conditions. When the movable portion is at or upstream of the datum position, there is no flow path between the fixed and movable portions. This enables the nozzle exit area to be optimized throughout flight, for example during changing cruise conditions, without inducing unwanted and inefficient flow structures between the fixed and movable portions and without allowing flow to leak out of the outer boundary of the nozzle.

Abstract: A method of operating a contra-rotating propeller engine that preferably comprises a 12 bladed front and a 9 bladed rear propeller. As is conventional, the engine is operated during at least a take-off phase, a cruise phase and an approach phase; during the cruise phase the engine operates with a generally constant propeller tip speed. The method is characterized by the step of operating the engine such that the tip speed of either or both of the propellers, during at least one of take-off, climb or approach, at least 10% greater than cruise tip speed. With a specific front to rear propeller spacing, increasing the tip speed reduces overall noise generated by the propellers.

Abstract: Disparities between optimum engine thrust for aircraft operation and power necessary to drive an ancillary machine such an electrical power generator can cause problems within a turbine engine. Clearly, it is necessary to continue developing sufficient electrical power for control and other systems within an aircraft despite aircraft thrust requirements. Previously, some compressed air flow has been bypassed in order to maintain compressor stability, but unfortunately such bypass systems within turbine engines can have a thrust recovery regime such that there is excess thrust in comparison with that actually necessary.

Abstract: A method of operating a contra-rotating propeller engine that preferably comprises a 12 bladed front and a 9 bladed rear propeller. As is conventional, the engine is operated during at least a take-off phase, a cruise phase and an approach phase; during the cruise phase the engine operates with a generally constant propeller tip speed. The method is characterised by the step of operating the engine such that the tip speed of either or both of the propellers, during at least one of take-off, climb or approach, at least 10% greater than cruise tip speed. With a specific front to rear propeller spacing, increasing the tip speed reduces overall noise generated by the propellers.

Abstract: Variation in the available mixing plane areas in an exhaust arrangement of a gas turbine engine enables alteration and configuration for better thermal cycle performance of that engine. A shaped centre fairing is associated with an exit nozzle and a bypass duct such that channels between the fairing, nozzle exit and duct can be adjusted to change the available areas. Such variation is achieved by relative axial displacement, typically of the exit nozzle using an appropriate mechanism.

Abstract: A fan turbine engine arrangement is provided in which a core engine is aligned such that an input of a nacelle is aligned with the upwash of a wing to which the arrangement is secured. The engine drives a fan such that bypass flows produced by the fan are guided by a duct to present a downward component for uplift. The core engine presents its output flow through a nozzle which is aligned with the fundamental axis Y—Y of the engine. In such circumstances, the bypass flows cross the core engine flow from the nozzle unless that engine is adjustable during operation in order to maintain alignment dependent upon lift requirements.

Abstract: A Turbine Engine and Method of Operating a Turbine Engine Disparities between optimum engine thrust for aircraft operation and power necessary to drive an ancillary machine such an electrical power generator can cause problems within a turbine engine. Clearly, it is necessary to continue developing sufficient electrical power for control and other systems within an aircraft despite aircraft thrust requirements. Previously, some compressed air flow has been bypassed in order to maintain compressor stability, but unfortunately such bypass systems within turbine engines can have a thrust recovery regime such that there is excess thrust in comparison with that actually necessary.

Abstract: A fan turbine engine arrangement 10 is provided in which a core engine 1 is aligned such that an input 11 of a nacelle 2 is aligned with the upwash of a wing 4 to which the arrangement 10 is secured. The engine 1 drives a fan 14 such that bypass flows 16 produced by the fan 14 are guided by a duct 8 to present a downward component for uplift. The core engine 1 presents its output flow through a nozzle 7 which is aligned with the fundamental axis Y-Y of the engine 1 in such circumstances, the bypass flows cross the core engine 1 flow from the nozzle 7 unless that engine is adjustable during operation in order to maintain alignment dependent upon lift requirements.