Abstract: A power unit for providing propulsive thrust includes an efflux duct defining a first fluid flow path along which gaseous fluid travels for discharge from a first fluid exit opening to provide propulsive thrust. The power unit also has a thrust reversing structure which, when in a deployed position, redirects the flow of gaseous fluid along a second fluid flow path to discharge from a second fluid exit opening to provide reverse thrust. The thrust reversing structure includes longitudinally translating cowl portions, which are moveable from a stowed position to the deployed position where the translating cowl portions block a major portion of the first fluid exit opening to cause gaseous fluid to efflux from the second fluid exit opening. The translating cowl portions move in a generally longitudinal direction towards the deployed position along a path which is inclined to the power unit axis.

Abstract: A power unit for providing propulsive thrust includes an efflux duct defining a first fluid flow path along which gaseous fluid travels for discharge from a first fluid exit opening to provide propulsive thrust. The power unit also has a thrust reversing structure which, when in a deployed position, redirects the flow of gaseous fluid along a second fluid flow path to discharge from a second fluid exit opening to provide reverse thrust. The thrust reversing structure includes longitudinally translating cowl portions, which are moveable from a stowed position to the deployed position where the translating cowl portions block a major portion of the first fluid exit opening to cause gaseous fluid to efflux from the second fluid exit opening. The translating cowl portions move in a generally longitudinal direction towards the deployed position along a path which is inclined to the power unit axis.

Abstract: A thrust reversing arrangement for an aircraft turbofan propulsive power unit includes a flow redirecting structure which has reverse flow enhancing sub-structures comprising: (i) a cavity which is so dimensioned as to generate a back pressure which supports redirection of flow; (ii) a cascade assembly which provides a flow control slot so dimensioned as to optimize reverse thrust for predetermined fan duct flow conditions; (iii) an obstructing duct wall portion having a leading edge so positioned as to form a leakage slot providing controlled leakage of forward flow; (iv) a box structure, the dimensions of which are such as to optimize back pressure in the cavity; and (v) provision for gaseous fluid under static pressure from the fan duct to load the redirecting structure to the inoperative position.

Abstract: A thrust reversing arrangement for an aircraft turbofan propulsive power unit includes a flow redirecting structure which has reverse flow enhancing sub-structures comprising: (i) a cavity which is so dimensioned as to generate a back pressure which supports redirection of flow; (ii) a cascade assembly which provides a flow control slot so dimensioned as to optimize reverse thrust for predetermined fan duct flow conditions; (iii) an obstructing duct wall portion having a leading edge so positioned as to form a leakage slot providing controlled leakage of forward flow; (iv) a box structure, the dimensions of which are such as to optimize back pressure in the cavity; and (v) provision for gaseous fluid under static pressure from the fan duct to load the redirecting structure to the inoperative position.

Abstract: In an aircraft propulsive power unit a thrust reversing arrangement includes a flow redirecting structure having a flow redirecting downstream wall against which gaseous fluid flow in a first flow direction impinges to turn the flow into a second flow direction to produce reverse thrust and an upstream wall round which the fluid flow turns and which has a boundary surface so formed as to support adherence of a boundary layer of the redirected fluid flow at the boundary surface. The upstream wall is provided with projecting elements to generate vortices which prevent or delay separation of the boundary layer from the boundary surface of the upstream wall. Alternatively, the upstream wall is formed with a plurality of flow apertures which are connected by a duct to a pressure differential region or source to cause gaseous fluid to flow through the boundary surface of the upstream wall to prevent or delay separation of the boundary layer.

Abstract: An aircraft propulsive power unit having an engine (20), a nacelle structure (12) which houses the engine (20) and which has an exterior low drag boundary surface (16) which is subjected to exterior air flow in a boundary layer adjacent the boundary surface (16) and an air flow disruption device (19) activatable to cause at a control location in the boundary surface disruption of exterior air flow in the boundary layer at the control location without reversal or deflection of engine thrust gaseous flow. Where the power unit is a turbofan and the nacelle structure includes a fan duct (22) with inner and outer fan duct walls (25,26) the air flow disruption device (19) is additionally or alternatively activatable to cause at a control location in the outer fan duct wall (26) disruption of air flow in the boundary layer at the control location.