Abstract: A engine such as a gas turbine engine has a bladed rotor 24 having variable pitch blades 8. In normal operation, the pitch angle of the blades 8 is controlled by a primary pitch control system. A back-up system is provided for controlling the blades 8, for example to displace them to a feathered condition, in the event of failure of the primary pitch control system. The back-up system comprises a pump 32 mounted on the rotor 24, and driven by relative rotation between the rotor 24 and a contra-rotating rotor 23. In response to a failure signal on a conduit 48, the pump delivers hydraulic fluid under pressure to a secondary actuator 30, which acts on the blade 8.

Abstract: Fuel control arrangements for gas turbine engines generally comprise an injector and a fuel control valve. Typically the fuel control valve is controlled in terms of fuel demand through fuel pressure presented to the valve. Fuel demand may vary and in such circumstances stagnation of fuel adjacent to the valve may cause degradation of the fuel and therefore spurious operational performance. By providing a dedicated working fluid, and typically hydraulic, pressure to the valve a variable aperture port can be displaced to alter the fuel flow configuration within the valve. In such circumstances different fuel valve conditions can be generated by altering the available area of aperture in the port to divert or present fuel to the injector between and across first or primary fuel paths and second or pilot fuel paths as required. Thus more flexibility with regard to fuel presentation to the injector is achieved as well as consistency with respect to avoiding fuel degradation as fuel demand varies.

Abstract: Fuel control arrangements provide and control fuel flow to injectors through fuel control valves. The injectors are connected to respective fuel control valves which in turn are connected to a first fuel flow path. The injectors are also connected to a second fuel flow path. The fuel paths are associated with a fuel source and generally have a recirculation valve between them. When flow in the flow path is stopped, recirculation of fuel can be provided across the recirculation valve to prevent fuel degradation. By provision of a restrictor valve in the second fuel flow path control of fuel recirculation can be achieved, as well as greater flexibility by presenting fuel flow separately through the second flow path to the injector whilst the first flow path is inhibited.

Abstract: In one aspect of the invention a method of manufacturing a thin wall isogrid casing by a chip machining process comprises the steps of: positioning a substantially cylindrical casing (10) on a support (20); the support having a substantially continuous cylindrical support surface (22) engaging at least part of the inner or outer surface of the casing; and machining a plurality of recessed pockets in the said inner or outer surface of the casing opposite the surface engaged by the said support; whereby the support reacts loads acting on the casing by the chip machining tool during machining to minimise distortion of the casing and tearing of the pockets being formed. With this method isogrid pockets (14) can be chip machined, by drilling and/or milling etc, with pocket wall thicknesses of less that 1 mm.

Abstract: A turbine blade for a gas turbine engine comprises an aerofoil having a suction and pressure side. The pressure side is provided with a reflex curvature at the aerofoil trailing edge region so as to reduce the thickness of the aerofoil in that region.