Abstract: The high pressure turbine of a gas turbine engine is provided with an annular array of aerofoil rotor blades which are surrounded by a shroud. The shroud is mounted on a tubular diaphragm which is deflected by pressure modulation to vary the effective diameter of said shroud means. An L-shaped cross-section flange provided on the turbine casing cooperates with a plurality of L-shaped cross-section hooks on the diaphragm to limit radially inward movement of the shroud and thereby prevent contact between the aerofoil blade tips and the shroud means.

Abstract: A gas turbine engine in which a rotating component (such as a turbine shaft or disc) is cooled by directing preswirled air at it by flowing the air along a passageway defined by the rotating component and a static wall. To reduce the viscous drag on the swirling air due to the presence of the static wall, the static wall is transpired to cause the boundary layer of air adjacent the wall to move in the same direction as the swirling air. The wall may be transpired by sucking or blowing air through air passages through the wall.

Abstract: A gas turbine engine bearing support structure comprises a central hub which carries a bearing and which is supported by a plurality of spokes from a ring member. The majority of the spokes are radially extending so that each is perpendicular to an imaginary tangent at its point of intersection with the ring member. However, two of the spokes are not perpendicular but are inclined so that compressive loading on the spokes results in partial rotation of the central hub, thereby leading to compressive loads in the non-inclined spokes being partially relieved by localised bending.