Abstract: A variable pitch arrangement to enable reverse pitch settings of fan blades to be achieved without the leading and trailing edges of adjacent fan blades abutting each other comprises two sets of fan blades and two sets of actuators. The two sets of fan blades are rotatably mounted on the fan rotor, and arranged circumferentially on the fan rotor. The blades in the first set of fan blades are arranged alternately circumferentially with the blades in the second set of fan blades. There are equal numbers of blades in each set of fan blades. The two sets of actuators act independently of each other on the two sets of fan blades such that the pitch of the blades in the first set and the pitch of the blades in the second set are varied in a phased relation to prevent fouling of the blades. Initially one set of blades varies pitch quickly while the other set of blades varies pitch slowly, and then the first set of blades varies pitch slowly while the other set of blades varies pitch quickly.

Abstract: The present invention relates to turbofan gas turbine engines. In conventional high bypass ratio turbofans the large variations in the free air stream flowing into the fan duct inlet is accommodated by a thick lip and a long, thick fan casing to prevent air flow separation from the outer surface of the fan casing, but produces a heavy fan casing and large drag values. In the invention a turbofan comprises a core engine which has a core casing, and a fan assembly positioned downstream of the core engine. The fans operate in a fan duct defined by the fan casing. The core casing has an external form upstream of the fan duct inlet which affects the airflow streamlines flowing into the fan duct inlet to cause it to adopt a flow path which is near alignment with the length of the fan casing to reduce fan casing weight, length and drag.

Abstract: A ducted fan gas turbine engine includes for surge control capability in the form of a downstream fan cowl portion which can be moved to open a gap of variable magnitude. Fixed cowl portion has a resilient downstream edge which effects a good seal against blocker flaps when not in use. The blocker flaps are moved across the fan duct on the cowl portion moving a sufficient distance in a downstream direction.

Abstract: Gas turbine engines, usually of the kind which include ducted fans, have cowl structures which generate drag inter alia by virtue of their frontal area. Where the cowl is of very large diameter i.e. in the order of 3 to 4 meters, if known devices such as thrust reverser cascades are installed in them, the frontal area and weight of the structure would be unacceptable. The invention provides a cowl structure of the magnitude mentioned hereinbefore, in which an improved cascade is installed. The or each cascade comprises a pair of rectangular frames which are joined by vanes. The vanes are pivotably connected to the frames in the manner of parallel rules as used in navigation. When non operative, the frames are stowed in superimposed relationship and thus enable a thinner cowl to be utilized than is possible in known cascade storage arrangements.

Abstract: A ducted fan gas turbine engine is provided with a fan cowling member made up of a static portion and an axially translatable portion. A plurality of rails interconnect the first and second cowling member portions and carry a generally annular array of airflow deflector vanes. The deflector vanes are normally stowed in stacked relationship when the cowling portions are contiguous but are equally axially spaced apart to define a fan air flow thrust reverser when the second cowling portion has been translated to a position downstream of the first cowling portion.

Abstract: In a gas turbine engine powerplant which has a requirement for both nozzle outlet area variation and thrust reversal, there is provided a common actuating means in the form of rams which firstly move a cowl portion so as to open a radial gap and thereby effectively increase the nozzle outlet area, and secondly move reverser cascades in a downstream direction into the gap created by moving the cowl portion. A lost motion device is fitted so as to enable achieving of the former movement without affecting the latter movement until such time as the latter movement is also required.

Abstract: The present invention relates to turbofan gas turbine engines in which the fan assembly is positioned downstream of the core engine of the turbofan gas turbine engine i.e. an aft fan turbofan. Conventional turbofan engines have the fan assembly positioned upstream of the core engine, and the core engine is mounted onto an aircraft pylon. The fan casing is then carried by the core engine. This arrangement in an aft fan would result in losses and intake distortions under side winds and aircraft yaw. The aft fan turbofan has a core engine and a fan assembly which is positioned downstream of the core engine. An upstream and downstream support means, which comprise struts, extend from a fan casing to the core engine and the fan assembly to support the core engine and fan assembly. Upstream mounting means on the fan casing and a downstream mounting means carry the turbofan engine from an aircraft pylon.

Abstract: A thrust reverser for a gas turbine engine of the type to power an aircraft, the thrust reverser comprising a first pair of half round doors nesting in a second pair of half round doors and both being pivoted on an axis extending diametrically of a jet pipe for the gas turbine engine. Each of the first pair of half round doors having a downstream edge which has a scarfed portion thereon and each of said second pair of half round doors having a downstream edge which is fully scarfed, the scarfed portion of said first pair of half round doors and the scarfed edges of said second pair of half round doors abutting when said doors are in a thrust reversing position with said second pair of half round doors preventing axial spillage of efflux. When said first pair and said second pair of half round doors are in non-thrust reversing position, said first pair of half round doors forming a greater portion of a nozzle throat and said scarfed portions of the downstream edges thereof reducing side spillage of efflux.