Abstract: The method comprises the steps of providing a substrate wafer (10); depositing a first layer of resist (12) upon the substrate wafer (10); removing selected areas of the first resist layer (12), thereby to provide first etch windows; forming first cavities (16) in the substrate wafer (10) by a first etching process through the first windows; bonding a relatively thick membrane wafer (24) to the substrate wafer (10), thereby covering the cavities (16); polishing the surface of the relatively thick membrane wafer (24) thereby to produce a relatively thin membrane (24a); depositing a second layer of resist (33) on the relatively thin membrane (24a); removing selected areas of the second deposited resist layer, thereby to provide second etch windows (40); etching away the relatively thin membrane (24a) in the region of the second etch windows (40) until the first cavities (16) are exposed, thereby to form in the relatively thin membrane (24a) a free standing resonator structure (18 ) suspended on a plurality of c

Abstract: A radar shield, in particular for an aircraft radar antenna, comprises a plurality of elongate triangular blinds 6 that may be stowed on individual rollers 7. To deploy the shield, the blinds are drawn from the rollers by wind-up spools to form a pyramidal shield within, for example, the aircraft radome assembly.

Abstract: Known polarization image detection systems produce an image illustrating structural information of a viewed scene which is representative of the degree of linear polarization. The present invention describes an improved detector system which enables more information to be extracted from the scene. The system comprises an optical arrangement having an optical axis (4) about which a retarder (1) and a linear polarizer (2) can be independently rotated, for producing a focussed image on a detector. This arrangement can be expressed mathematically in terms of Stokes parameters and Mueller matrices, and the expression can then be solved to provide three different polarization images representative of the viewed scene.

Abstract: This invention relates to improvements in so-called "virtual reality" computer systems. The display system described enables the effective integration of computer generated images and real, naturally occurring images in the visual display units which provide the user with his entire visual stimulation. Areas of the user's notional field of view where computer-generated imagery is required (for example the cockpit canopy in an aircraft flight simulator) are coloured with a predetermined colour or intensity. Two video cameras are provided, each of which is mounted so that its field of view corresponds to a respective one of the notional fields of view of the user's eyes. The signals from the video cameras are analysed to determine the presence of the predetermined colour or intensity, thereby giving an indication that a computer generated image is required for that part of the video camera's field of view.

Abstract: A variable cycle gas turbine bypass engine includes a first fan 1 located at an inlet to the engine so as to provide air to a compressor 2 driven by a turbine 11 and to a bypass duct 13 surrounding the compressor housing. A second fan 5 located in the bypass duct 13 is driven by a free turbine 12. A controllable area auxiliary air intake 4 and bypass duct blocker doors 3 are located between the first and second fans 1, 5. Control means are effective for selectably operating the bypass duct blocker doors 3 and the auxiliary air intake 4 to vary in operation the bypass ratio of the engine. Thus in conventional wing-borne flight, the intake 4 is closed and the bypass duct 13 is unobstructed, and the combined exhausts from the bypass duct 13 and the turbines 10, 11 and 12 pass to a tailpipe 14, which has a vectorable nozzle 8, to produce forward thrust.

Abstract: A video circuit which enables three full color VDU's (6a, 6b, 6c) to be driven by only one color graphics generator (2). The Circuit has many uses including the generation of head down displays for flight simulators.

Abstract: A process is described of forming a diffusion bonded article from components made of aluminum or an alloy thereof that forms a protective coating of an oxide that inhibits such bonding. The process comprises removing the oxide layer and immediately forming the components into a stack, placing the stack in the chamber of an electron beam welding device, evacuating the chamber and electron beam welding the edge regions of the stack; the welded stack can then be diffusion bonded at leisure without the oxide re-forming. The diffusion bonded article can be superplastically formed to a finished or semi-finished shape.

Abstract: A control mechanism for a displaceable control member such as an aircraft pilot's "joystick" includes an array of pressure transducers (20) in contact with a pressure plate (22) which in turn is in pivotal connection with the control member (10) operated by the pilot. Adjustable springs (26) bias the pressure plate (22) towards the transducers (20). Pivotal movement of the control member (10) tends to compress the springs (26) and to cause the transducers (20) to generate output signals representative of differential pressure. The signals are then processed by circuitry (34) to provide inputs to flight control computers.

Abstract: A stabilization system for a towed aerodynamic body 1. The body is provided with two, contra-rotating tubular shrouds 3, 4 each fitted with a set of vanes 5, 6. When the towed body is disturbed by the towing aircraft's wake, the gyroscopic inertia caused by rotation of the shrouds exerts a damping effect on the subsequent oscillatory motion of the towed body. In one embodiment, the shrouds are coupled by wheels which constrain the shrouds to rotate in opposite senses. Hence gyroscopic precession effects due to each rotating shroud cancel.

Abstract: An apparatus for lubricating a slow cycle stroke mechanism, such as that found in a wing flap of an aircraft. The lubricating apparatus moves in conjunction with the wing flap and replenishes lubricant to a ball screw actuator driving the wing flap. The apparatus includes a reservoir and a pumping mechanism for pumping lubricant from the reservoir to the ball screw actuator. A plunger reciprocates within a cylinder to pump lubricant. A compliant element that includes an end stop is positioned to prevent over travel by the plunger and to thereby prevent damage.

Abstract: The present invention provides a method of making a domed structure using superplastic forming and diffusion bonding techniques. The dome is of a deep and/or irregular shape that cannot be achieved by creep forming. The method includes the step of forming a stack of two or more sheets made of superplastic material and the sheets of the stack being joined together in face to face contact by metallic bonds such that no sheet in the stack is bonded to more than one of its neighbouring sheets; the metallic bonds preferably lie on lines extending radially from and/or circumferentially around the said peak. The resulting stack is heated to superplastic termperatures and a pressure differential is established across the stack to form it into a domed shape.

Abstract: A fibre optic gyroscope including a fibre optic loop, a radiation source for generating a broadband signal, splitting means for splitting radiation from the source into two components and inserting them into the loop in clockwise (CW) and counter clockwise (CCW) directions, recombining means for recombining the components interferometrically to give an indication of rotation rate of the loop, characterized in that there is further provided amplification means for amplifying both components travelling within the loop.

Abstract: An ejection seat (1), supported on ejection gun guide rails (2) and moveable between an upright position to a reclining position thus affords the pilot greater protection from the effects of high "g" forces. Movement of the seat (1) is effected by hydraulic acutators (3), (4), guided by an arcuate track (15). The invention has the further advantage of allowing ejection from an upright or a reclining position or any intermediate transitional position.

Abstract: To overcome Kerr effect induced gyro bias in a ring resonator optical gyro, the intensities of the beams travelling in opposite directions around the ring have to be very accurately matched. To achieve this a ring resonator gyro includes a first optical coupler (6), the coupling ratio of which is variable and which divides light from a laser (1) into a first and a second component of generally equal intensity, a second optical coupler (8) which transmits a predetermined proportion of the first component to one input of the ring resonator (15) for transmission around the ring resonator (15) in one sense, and a third optical coupler (9), the coupling ratio of which is variable to couple a variable proportion of the second component to the other input of the ring resonator (15) for transmission around the ring resonator (15) in the opposite sense.

Abstract: In a superplastic forming/diffusion bonding process, in particular for aluminum-lithium alloys, the stop-off material in the diffusion bonding step is a porous lamellar material such as glass cloth or vermiculite paper. In one embodiment, prior to diffusion bonding, the stack of alloy sheets and lamellar material may be sealed under vacuum.

Abstract: Control apparatus, such as an aircraft throttle box, includes a manual control member 8 linearly movable on a first shaft 2. The position of the control member is sensed by rotation of the shaft 2 to generate an output control signal. In order to balance the apparatus, especially against high g-forces, a second shaft 3 is provided, parallel to the first carrying a counterweight 13 that moves together with the control member 8, but in the opposite direction.

Abstract: Information transmitting method using a laser beam projector which may form part of an optical missile guidance system on board a ship say. For missile guidance, the laser beam is so scanned over a field containing the target and missile that the missile receives successive glimpses of the beam at times dependent on guidance and other information to be sent to it. For transmitting information, to another ship say, the same beam projector is used to scan a field containing a detector on board the other ship so that the detector receives successive glimpses of the beam at times dependent on the information to be transmitted.

Abstract: A fire and smoke suppression system suitable for passenger aircraft capable of `surviving` a crash consists of a plurality of individually and independently operable unit (17) each including its own self-contained supply of fire/smoke suppressant, such as water, as well as its own self-contained supply of a pressurizing device, such as CO.sub.2 bottle (23) which, on activation, expels the suppressant under pressure. Each unit (17) is an integrated assembly including a spray head (18) terminating in a nozzle (20) in flow communication with a flexible bag tank (25) containing water and accommodated in a rigid outer shell (24).

Abstract: An aircraft wing leading arrangement includes a forward slat (10) movable between a stowed position and a deployed position in which a slot (13) is revealed. To prevent undesirable flow disturbances in the slot (13), a shutter device is provided for the aperture (22) in the leading edge through which the slat actuator mechanism (14) protrudes in the deployed position. This shutter device consists of a sprung (38) panel (30) of flexible material pivotally movable between aperture-blocking and aperture-unblocking positions.

Abstract: A process is described of preparing composite articles of aluminium or aluminium alloy suitable for superplastic forming by explosion welding two or more components together and heating the welded article to consolidate the bonds. The welds do not extend into areas to which a stop-off composition has been applied and the article can be superplastically formed by passing a pressurized fluid into these stopped-off areas.