Abstract: A noise attenuation panel for an aircraft engine nacelle structure comprises a cellular core having a multiplicity of cells and a facing sheet having a multiplicity of holes which provide for gaseous fluid communication between the cellular core and the front face of the facing sheet. Each hole in the facing sheet has a bore diameter which increases along the bore in the direction of the rear face of the facing sheet throughout the bore or a part of the bore and which does not at any point of the bore decrease along the bore in the direction of the rear face of the facing sheet. Prior to assembly of the facing sheet and the core the holes are formed by electron beam drilling from an entrance face of the facing sheet through to an exit face and the facing sheet and the cellular core are assembled to form the panel in such disposition that the exit face forms the front face of the facing sheet and the entrance face forms the rear face of the facing sheet.

Abstract: In forming a multi-axial yarn structure a bias yarn assembly forming device makes use of cooperating yarn guide and yarn transfer members having yarn guide elements defining guide and transfer openings which hold warp yarns spaced apart in the weft direction. Warp yarn transfer from an opening in one member to an opening in the other member is facilitated by providing the guide elements of the two members with cooperating complementary salient and re-entrant inclined end portions. Furthermore, a yarn diverter blade extends from the end portion of each guide element of one of the members to hold the transferring yarns away from the junctions between the cooperating end portions of the guide elements. To facilitate insertion of binding warp yarns two sets of yarn guide and yarn transfer members are provided to hold the yarns spaced apart to form binding warp yarn insertion zones between the two sets.

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: A guidable flying body of the type in which a pitch control signal from a station remote from the flying body is received by the flying body to control the pitch of the flying body. The flying body is provided with height control in which the height of the flying body is sensed from the flying body and, as the flying body approaches a predetermined minimum height, the pitch control signals are so modified after reception by the flying body that the flying body is controlled to maintain at least said predetermined minimum height.

Abstract: In a loop holding mechanism (31), loop engaging pins (39) which are carried by pin blocks (38) are arranged successively to engage at a feed end (310) of the mechanism loop portions of yarns formed at opposite side edges of a multi-axial yarn structure being formed. The pin blocks (38) at each side of the mechanism (31) advance in abutting relationship along an advancement track (32) to a delivery end (311) of the mechanism (31) where they are returned along a return track (34) and again engaged in the successively formed loop portions.

Abstract: An aircraft propulsive power unit comprises an engine, a nacelle structure which houses the engine and which includes displaceable nacelle portions which form a forward part of the nacelle structure and which take up operational positions in which a forward end of each nacelle portion forms part of an intake opening which leads to an intake barrel which is located upstream of the engine for the supply of intake air to the engine and which is secured to a forward component of the engine. Each displaceable nacelle portion includes a lipskin structure which has rearwardly extending outer and inner lipskin edge portions, and further includes an outer main skin.

Abstract: A method of producing a structural component (12) from a primary wall structure (14) which defines a plurality of juxtaposed primary cells (15) which extend between and which are open to the front face and the rear face of the component (12) and a secondary wall structure (16) within the primary wall structure (14) which divides each primary cell (15) into two or more subcells (151, 152) comprises first forming the primary wall structure (14) and then forming the secondary wall structure (16) within the primary wall structure (14) by bringing the primary wall structure (14) into a condition in which it lies within a body of liquid the surface of which provides or is provided with a photosensitive layer and in which the photosensitive layer is at a predetermined level in each primary cell (15) and exposing the photosensitive layer to a radiation source to bring the photosensitive layer to a consolidated state within the primary wall structure (14) to form the secondary wall structure (16).

Abstract: A device for forming from warp sheet a bias yarn assembly comprising two superposed bias yarn sub-assemblies in which the bias yarns of one sub-assembly are inclined to the bias yarns of the other sub-assembly and in both of which the bias yarns are inclined to the warp feed direction includes a yarn transfer mechanism having a lower yarn guide member with upstanding yarn guide elements which extend through the thickness of the warp sheet and define warp yarn guide openings through which the warp yarns of the warp sheet pass and which hold the warp yarns in positions spaced apart in the weft direction and an upper yarn transfer member which includes yarn guide elements which extend downwardly and which define transfer openings for the reception of yarns of the warp sheet from the yard guide openings for transfer to the other yarn guide openings.

Abstract: An aerodynamic low drag structure (12) has a skin (18, 19, 20) which in movement of the structure (12) relative to a surrounding gaseous fluid medium produces at a flow control region of the skin (18) laminar flow in a boundary layer adjacent the skin. To improve boundary layer control, gaseous fluid is withdrawn from the boundary layer at the flow control region into a first inlet opening (21, 22, 23) in the skin (18) and is conveyed along a first fluid flow path (241, 242) within the structure (12) for discharge at a discharge opening (28) downstream of the first inlet opening (21, 22, 23). Gaseous fluid is withdrawn at a second inlet opening (26) in the skin (20) at a region of the skin subjected to gaseous fluid at ramming pressure and conveyed along a second fluid flow path (27, 242) within the structure to the discharge opening (28) or a further discharge opening.

Abstract: Boundary layer separation at the boundary surface of an intake duct (18) of a turbofan aeroengine nacelle (12) at conditions of high incidence and high engine mass flow arises from shockwave induced pressure gradients in the boundary layer. To control separation, gaseous fluid is withdrawn from a high pressure region of the boundary layer at a downstream region of the boundary surface, conveyed within the intake duct structure (19) and discharged at an upstream region of the boundary surface into a low pressure region 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.

Abstract: An aircraft propulsive power unit (19) comprises a nacelle structure (20) housing an engine and having a forward nacelle portion (21) and a rearward nacelle portion (131). The rearward end of the forward nacelle portion (21) in an operational position adjoins the forward end of the rearward nacelle portion (131) and the forward end of the forward nacelle portion (21) includes an intake opening leading to an intake barrel (28) upstream of the engine for the supply of intake air to the engine.

Abstract: A ducted fan turbine engine includes a nacelle and an outer discharge nozzle mounted on an aircraft wing by a pylon. The nacelle includes to parts which are hinged to the pylon for pivoting movement between an open position and a closed, operational position. Each nacelle part contains a bypass air duct. Spaced spigot locators and blade locators are positioned at the forward edge of the discharge nozzle and spigots and blades are correspondingly located round the rear edge of the nacelle parts. The locators and their corresponding spigots and blades are arranged so that on closure of the nacelle parts they engage one another and transmit the flight loads through the nacelle.

Abstract: A noise attenuation panel having a backing sheet, a facing sheet and a cellular core having a multiplicity of open-ended juxtaposed cells. The backing sheet extends across the ends of the cells at the rear of the core and the facing sheet extends across the ends of the cells at the front of the core. The facing sheet is made of a porous permeable thermoplastics material. The porous permeable thermoplastics material for the facing sheet is produced by powder sintering a thermoplastics material.

Abstract: In a method of and machine for forming a non-woven bias yarn assembly comprising two superposed non-woven bias yarn sub-assemblies each yarn is transferred by a yarn transfer member from an opening it occupies in a yarn guide member to another opening in the yarn guide member in such a manner that each yarn is caused in a succession of forward transfer steps to follow the yarn preceding it from one opening to another along a non-intersecting path until the yarn at a first end opening in the path arrives at a second end opening in the path located at the opposite end of the path and the yarn at the second end opening in the path arrives at the first end opening and then in a succession of return transfer steps to follow the yarn preceding it from one opening to another along the non-intersecting path in the opposite direction until the yarn from the second end opening in the path arrives at the first end opening and the yarn from the first end opening arrives at the second end opening.

Abstract: A structural assembly comprises first and second closure parts displaceable between a closed disposition in which they are locked by a locking mechanism and in which they close off the front side of the closure parts from the rear side and an open disposition in which they are spaced apart for access to the rear side of the closure parts and a default indicating device comprising a projection element (34) which is movable to the rear side of the closure parts where it is stowed and which releases when the closure parts move to an open disposition and moves to a projecting position in which it projects from the rear side to the front side of the closure parts to provide a visual warning that the closure parts are not in the closed disposition. The closure parts in one embodiment are fan cowl doors of an aero engine nacelle which are hinged at their upper edges to the upper part of the nacelle and which have bottom edges which move into the closed disposition at the base of the nacelle.

Abstract: A filament reinforced perforate composite sheet is manufactured by forming a filament assembly which includes reinforcing filament structures and passage forming filament structures and in which the passage forming filament structures extend from the front face to the rear face of the assembly, applying a matrix material to the assembly to form a composite sheet in which the passage forming filament structures extend from the front face to the rear face of the sheet and removing the passage forming filament structures or a part or parts thereof to produce a multiplicity of passages extending through the composite sheet.

Abstract: A control signal transmission circuit for transmitting a control signal to a controllable device (21) to control the controllable device (21) and to protect the controllable device (21) against control by component failure generated signals.

Abstract: A process for weaving using a reed having vertically aligned upper and lower reed portions with the reed portions being relatively movable in a weft direction. The process includes transferring warp yarns between the reed portions, moving the transferred warp yarns in the weft direction to define a selected array of warp yarns, and then shedding the array of warp yarns for insertion of weft yarn. A weaving loom head is also provided including a reed having vertically aligned upper and lower reed portions, a plurality of healds each releasably engagable with an individual warp yarn for moving selected warp yarns from one reed portion to the other, and a selectively operable drive mechanism for causing relative movement between the reed portions by a predetermined spacing in the weft direction. Weaves may accordingly be produced including warp threads extending parallel to and/or inclined to the fabric take-off direction. Inclination of the warp threads may be in a horizontal and/or vertical plane.

Abstract: A structural component exposed to lightning strikes comprises a bonded assembly of a first component part (18) which has a cellular structure and a front face (20) and a second component part (22) extending across the front face (20) of the first component part (18), the second component part (22) comprising an electrically conducting first sheet (23), an electrically non-conductive second sheet (25) at the rear of the first sheet (23) and a fibre reinforced composite third sheet (26) at the rear of the second sheet (25) and positioned between the second sheet (25) and the front face (20) of the first component part (18). In one form, the electrically conducting first sheet (23) is a non-ferrous metal or metal alloy expanded foil, the electrically non-conducting second sheet (25) is a glass fibre fabric, the third sheet (26) is a carbon or graphite fibre reinforced composite sheet and the first component part (18) is an aluminium alloy honeycomb core.