Abstract: A surface-discharge igniter is formed by positioning a tubular assembly coaxially within the outer shell of a nose portion of the igniter. The assembly is welded about one end to form a seal with the outer shell, and glass material is placed within the assembly to form a seal with a central rod-shape electrode extending coaxially within the assembly. The assembly has an outer tube of the same material as the outer shell, and an inner tube which extends coaxially within the outer tube and which is of a different material, having a coefficient of thermal expansion substantially the same as that of the glass material. The inner tube is joined to the outer tube at an end remote from the seal with the outer shell. The nose portion forms the operative tip of the igniter and is welded to a rear body portion having screw threads for mounting the igniter and for making electrical connection to it.

Abstract: A fibre-optic cable includes a fibre-bundle, for transmitting light along the cable, that is sealed at either end to a metal ferrule. Each end of the fibre-bundle projects a short distance from its respective ferrule and is enclosed by a metal collar which is welded to the ferrule. The projecting ends of the fibre-bundle are sealed to the ferrules by melting a glass tube within each collar about the ends of the fibre-bundle. A thread of glass or Silastomer material extends between the two ferrules and is helically wound about the fibre-bundle so as to hold together the fibres of the fibre-bundle. Convoluted outer metal tubing extends about the fibre-bundle and is welded at each end to respective ferrules. The fibre-bundle is cushioned within the outer tubing by a sleeve of woven fibre which also extends between the two ferrules about the fibre-bundle and the helical thread.

Abstract: An aircraft-speed indicating instrument has an index which is movable against a scale to provide a reading of airspeed, and a digital indicator which is selectively operable to provide a digital reading of either Mach number or the airspeed. The index and the digital indicator are driven by respective control systems supplied with a multiplexed electrical signal containing information representative of both Mach number and airspeed. Each control system includes gating means which is operable to pass only those parts of the multiplexed signal necessary for the associated control means to provde the desired reading.

Abstract: A head-up display system for an aircraft has a display unit which projects a display of symbology representing the aircraft flight parameters onto a separately mounted partially-transparent reflector positioned in front of the aircraft pilot, so that the pilot sees an image of the display against the external scene. The display unit has a sensor which receives an image of the display via the reflector. The sensor responds to displacement of this image from a reference established with respect to the display unit, caused by movement of the reflector relative to the display unit, and the display is correspondingly modified to compensate for such movement. The display unit may include a cathode-ray tube for providing the display which can be modified by adjustment of the deflection of the cathode-ray beam. In this case the reference established with respect to the display unit may be an instantaneous point image of the cathode-ray beam.

Abstract: A pressure transducer has a capsule having two chambers separated from one another by a diaphragm. The capsule is made entirely of a glass-ceramics material, such as, lithium alumino silicate. One of the chambers is sealed and has a lens with a curved surface adjacent the diaphragm such that, when the capsule is illuminated, a Newton's Rings pattern is produced by interference between light reflected from the surface of the lens and the diaphragm. Pressure is communicated to the other chamber so as to cause the diaphragm to be deflected into or out of the sealed chamber with a consequent shift in the interference pattern which is used to provide a measure of the pressure change. The capsule also has two further chambers which are identical to the first two chambers and which are both sealed. One of these further chambers is illuminated to produce a second interference pattern.

Abstract: The spiral grooving of a thrust-plate of an aerodynamic gas-lubricated bearing is formed by ionic bombardment of a flat face of a machined blank. The face is masked to leave exposed only those areas where material is to be removed. Grooving on a cylindrical surface of a spindle is similarly formed, the cylindrical blank being rotated to present the unmasked areas successively and repeatedly for bombardment.

Abstract: An indicating instrument particularly for use in a vehicle comprises a first element which is moved behind a window of the instrument such that the amount of the first element visible in the window is indicative of the distance travelled by the vehicle, and a second element that is moved in dependence upon the speed of the vehicle and such that the second element is obscured from view in the window by the first element while a predetermined relationship exists between the speed and distance.

Abstract: A fluid pressure supply apparatus includes a fluid pressure source, a fluid supply circuit to receive fluid under pressure from the fluid pressure source, and a fluid return circuit. These circuits are to be coupled to an hydraulic motor through first and second fluid paths. The supply apparatus further includes first means to couple the fluid supply circuit to the first fluid path to cause the hydraulic motor to be operated by the fluid pressure in a predetermined sense, and second means simultaneously to couple the second fluid path either to the fluid supply circuit, to provide a regenerative coupling for the motor, or to a fluid return path. This latter coupling is initially to the second fluid path, the second means being arranged to transfer that coupling from the fluid supply circuit to the fluid return path during operation of the motor in the predetermined sense.

Abstract: A push-button mechanism for tuning a radio receiver includes push-buttons that are actuable to rotate a turrent tuner to different extents for station selection. The side of each push-button contacts one end of an individual lever to pivot it through a predetermined angle upon actuation of the push-button. The other end of the lever contacts one of several projections on a bar which extends transversely of the push-buttons and which is coupled via rack and pinion gearing to the drum of the turret tuner. The levers of the different push-buttons have different orientations with respect to the bar so that although each lever is pivoted through the same angle, longitudinal displacement of the bar effected, and hence the setting of the turret tuner, depends upon which push-button is actuated. Upon actuation of a push-button, the bar is locked in its displaced position by means of a leaf spring, and the drum is then locked in position by means of a projection that engages in one of several notches in the drum.

Abstract: A surface-discharge igniter for a gas-turbine engine has a pellet of rod shape a part at least of the pellet surface being semiconductive so that when voltage is applied between electrodes connected at either end of the pellet it causes electrical discharge along its length. The pellet may, in one arrangement, be mounted to be a tight fit within the central-section of a key-hole bore which extends axially through a ceramic block within the igniter's outer metal shell. A strip of the pellet surface is exposed along the radially-divergent section or discharge cavity of the bore and discharge along the strip generates a plasma flame within the cavity that bursts forth through an aperture in the bottom electrode at the tip of the shell. In another arrangement the rod-pellet is mounted at the end of a mineral-insulated cable, coaxially within a cylindrical cavity. The pellet may alternatively be mounted to extend transversely of the igniter and to be exposed along its length at the operative tip of the igniter.

Abstract: An instrument for providing an altitude representation in accordance with ambient atmospheric pressure has a mechanism that is manually-operable to effect adjustment to the setting of a datum against which the representation is provided. A mechanical feedback is applied to the mechanism in accordance with the datum setting such that the setting of the datum depends both upon the manual operation of the mechanism and the feedback applied to the mechanism as a result of that manual operation. The mechanism may include a worm gear that is rotatable in accordance with manual operation of the mechanism in which case the feedback is introduced into the mechanism by longitudinally displacing the worm gear.

Abstract: A thermocouple-probe assembly for use in the measurement of temperature in a gas-turbine engine. The assembly has a central hub which is for mounting on the central exhaust-cone of the engine and twelve elongate thermocouple probes which extend radially from the hub such that their operative tips are located in the gas flow through the engine. Each probe has two Chromel-Alumel junctions at its operative tip, the junctions of each probe being electrically interconnected by means of four concentric electrically-conductive rings which are mounted coaxially within the hub. Two of the rings are of Chromel and two of Alumel, the wires forming the thermocouple junctions being connected to rings of the same material by means of small edge portions of the rings which are turned back and crimped around each wire. External electrical connection to the probes is made by cables connected to the rings within the hub.

Abstract: A quadruplex, double-failure survival, fly-by-wire aircraft control system includes two monitor lanes whose outputs are consolidated with those of the four main control lanes to drive the aircraft control-surfaces by hydraulic rams via individual spool-valve actuators. Nominally-identical sets of pilot's-demand, instrument, and position-feedback signals are derived independently for the four lanes respectively, and digital representations of all these are exchanged between the control lanes for the selection of their mean or median values by digital processors that also serve to compute the control outputs of the lanes from the selected values. The sets of signals supplied to one pair of the four lanes are reversed in sense compared with the sets supplied to the other pair so as to ensure that the same digitally-encoded data is represented differently in the different pairs and the possibility of a context-dependent failure occurring simultaneously in both pairs is thereby avoided.

Abstract: A head-up display involving display of pitch-bar symbols in the line of sight of an aircraft pilot is generated using raster scanning of a cathode-ray-tube screen and bright-up in accordance with stored information relating to the wings-level or other datum attitude of the aircraft. Variation of the pitch-bar mapping in the display area to follow change of attitude of the aircraft is made through transformation in accordance with pitch and bank angles applied to the point-by-point progression of the raster scan, and the visual staircase effect of symbols inclined to the line-scan is reduced by controlled variation in brightness from point to point. Each point (x.sub.d, y.sub.d) in the progression of the scan through the display area is mapped back incrementally into the corresponding point (x.sub.p, y.sub.p) of the stored datum-attitude map, through a transformation in rotation dependent on the bank angle .phi.. Computation of x.sub.p involves summation of discrete signals representative of x.sub.d cos.phi.

Abstract: A flexure-pivot for providing resilient restraint that opposes relative angular displacement between two members involves two flat springs, that are held at one end between pairs of pins carried by one member and at the other end between pairs of pins carried by the other member, the flat springs each having two parallel rib portions that are linked at one end and are interlaced with one another. In one form of flexure-pivot the unlinked end of both the rib portions of each spring is secured between a pair of pins carried by one member and the linked end of both the rib portions of each spring is secured between a pair of pins carried by the other member.

Abstract: A display device includes a layer of electroluminescent material which is capable of conducting electric current. The electroluminescent material is sandwiched between a pair of electrodes to which a voltage is to be applied to excite the electroluminescent material to luminescence. The display device is manufactured by disposing on an assembly comprising a substrate with one of the said electrodes thereon, two masks in which are formed aligned apertures defining a region in which the electroluminescent material is to be provided. The electroluminescent material is disposed in the apertures, and, after that material has solidified one of the masks is removed, the other of the electrodes then being formed on the exposed surface of the electroluminescent material and within slots in the remaining mask and the mask is removed.

Abstract: In a driving mechanism of the kind having a drive part and a driven part with a shear-type coupling therebetween, the drive and driven parts have respective cylindrical surfaces which are spaced apart from, and substantially coaxial with, one another to define an annular space centered on the rotational axis of the parts. A fluid is disposed in the annular space to provide, at least in part, the said shear-type fluid coupling, and the spaced cylindrical surfaces together with the fluid therebetween constitute the sole bearing for the drive part. The fluid may contain an anti-creep additive. One of the said cylindrical surfaces, preferably the inner circumferential surface, may be constituted, at least in part, by a porous member impregnated with a shear-type fluid.

Abstract: A rack for mounting electronic equipment comprises two spaced plates each having a series of aligned channels. Each item of electronic equipment is carried by a frame which is located in the guideway defined by an opposed pair of channels, and the frame is individually clamped in each channel. Large items of equipment are held in several frames interconnected by resilient metal strips, but each frame is still individually locked in its respective pair of channels. Thus each frame has an independent thermal path to each plate, with predictable, uniform characteristics; in addition, the entire assembly is resistant to dynamic loads. The plates and/or the frames may be force-ventilated.

Abstract: In a moving-coil electrical instrument the electric coil is rotatably mounted on a spindle for angular displacement about the axis of the spindle. The ends of the spindle are located in respective bearings disposed in apertures of a frame and each bearing has a part that is angularly displaceable about the axis of the spindle between a first angular position in which the part supports the spindle and a second angular position in which that part is removable from the respective aperture. The coil is mounted on a support through which the spindle extends and carries a body to counter-balance the coil. The center of mass of this body is spaced from the plane which includes both the center of mass of the coil and the spindle axis. The support also carries a counterpoise body that is spaced from the counter-balance body about the spindle axis.

Abstract: Diesel engine speed is sensed by a thermistor which is disposed within an air inlet of the engine manifold so that the resistance of the thermistor varies in accordance with the temperature of the air within the inlet and thus in accordance with the speed of the engine. The thermistor is connected in a transistor circuit which derives, in response to the change in resistance of the thermistor, an electric signal having a frequency which varies in accordance with engine speed.