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 deglitch circuit is provided to connect a source of changing voltage or current to a utilization device to eliminate unwanted voltage excursion contemporaneous with changes in amplitude. The deglitching circuit includes one transformer winding with a center tap connected to the source and a pair of serially connected diodes connected to terminals of the winding. Another winding of the transformer is connected to a source of potential through switches which allow the other winding to alternately conduct current in one or another sense. Changes in the sense of current conduction through the other winding induce a voltage into the one transformer winding. Depending on the change in current this voltage may forward bias the diodes and provide the effect of a closed switch between the source and the circuit output, which is taken at the junction of the diodes.

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: A counter-pointer display of aircraft altitude is driven by a servo in accordance with a digital representation of height provided at regular intervals by an air-data computer. The content of a first register is updated regularly with the height representation, and the difference between this and the content of a second register is entered into a third register. The content of the second register is updated rapidly from a shaft encoder that is coupled to be driven together with the counter-pointer display by a stepping motor, and the content of the third register is updated in synchronism with the updating of the first register to staticize the error between the input height-representation and the output representation provided by the counter-pointer display.

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.

Abstract: Two thermocouple junctions of a gas-turbine thermocouple probe are provided by junctions between respective pairs of wires that form the inner conductors of a metal-sheathed mineral-insulated cable. External electrical connections to the pairs of wires are established at a ceramic support block into which the cable extends, the connection in each case being made by a thicker wire that extends completely through the block from the opposite direction of the cable, and then turns back on itself to extend through the block again and emerge adjacent the end of the cable. The thin inner conductors of the cable are twisted about the projecting ends of their respective connecting wires and welded to them to complete the connections.

Abstract: A tubing adaptor of unitary plastics construction is assembled with an endotracheal or other medico-surgical tube for coupling the tube to a connector or tubing of larger diameter in a gas circuit. The adaptor has a tubular stem which closely fits into the tube and which extends from, and opens through, the base of the cup-shape body portion. The cup-shape body portion is for insertion in the passageway of larger diameter to establish the coupling, and the tubular stem is turned back on itself at its open end remote from the base so as to provide an external circumferential claw or lip that is splayed outwardly away from the open end so as to engage with the inside of the tube to restrain withdrawal of the stem from the tube. The claw may be formed by a step which involves the application of force uniformly around the whole circumference of the open end of the stem after that end has been splayed outwardly, against an inclined circumferential shoulder of a spigot.

Abstract: A two-part electrical connector for connecting a cable from a cathode-ray tube to an E.H.T. power-supply unit is incorporated in a safety interlock which ensures that E.H.T. is applied to the female part of the connector mounted on the unit only while the male connector part on the cable, is fully mated with the female part. Application of E.H.T. to the female part is controlled by a switching device that is operated via an interlock circuit only when two pins on the female part are bridged electrically by contact under a resilient-wire loop carried by the male part. The loop is sprung onto an electrically-insulative collar that embraces coaxially a tubular nose of the male part, and the pins project at diametrically-opposed positions through a flange of a tubular guideway of the female part. The pins enter slots in the collar and abut the wire within the loop such as to maintain the interlock circuit closed and apply E.H.T.

Abstract: A head-up display system in a military aircraft provides projection of flight and weapon-aiming information into the pilot's line-of-sight through a partially-transparent reflector. The pilot operates a button firstly when he recognizes a target viewing through the display and then again when he fixes his eye on an aiming marker in the display. On each occasion of button operation a measure of his eye position is entered into the system to derive coordinates of the identified target related to the marker position in the display, for generation of the appropriate shifts to move the marker into register with the identified target. The measure of eye position is provided in each case by analysis of video-signal waveforms derived by a vidicon camera that is carried on the pilot's helmet and scans reflection in the helmet-visor of the pilot's eye as illuminated, also by reflection in the visor, from an infra-red source.

Abstract: Control apparatus for controlling an aircraft gas-turbine engine, having two control lanes operated in parallel with one another and each of which is capable of performing the function of the control apparatus individually, includes a computer and a monitor unit associated with each lane for performing checks on the integrity of the components of both lanes. Transducers in each lane sense engine parameter values and pass signals in accordance therewith to the computer that sends control signals to a control unit and thence to an actuator for adjusting engine variables in accordance with engine-thrust requirements. The control unit includes a pair of cam-operated switches that respond to difference in the values of the control signal from each lane indicative of a fault in the lanes and that trigger operation of the monitor unit in each lane.

Abstract: A radiation-detecting device which is mounted on a gas-turbine engine to receive radiations from the afterburner combustion-zone, includes a gas-filled electrical discharge tube that is located within a tubular nose of the device and is pulse energized. The ultra-violet component of radiations from the zone and distinctive of the presence of flame in the afterburner, is transmitted to the discharge tube via a sapphire plano-convex lens, the infra-red component being attenuated by a thin gold-film coating on the planar face of the lens, whereby discharge takes place in the tube with each energizing pulse only while the flame is present. The sensitivity of the detecting device to ultra-violet radiation is enhanced by internal reflections from reflective coatings on the inner surface of the tubular nose and the glass envelope of the discharge tube.

Abstract: A method of manufacture of a semiconductor pellet of an electric surface-discharge igniter of a gas-turbine engine begins with a mixture of 60% by weight silicon-carbide particles of 600 British Standard Mesh size, and 40% by weight of powdered alumino-silicate or other silica glass, containing 85% silica. The mixture is heated to 1250.degree. C. to coat the silicon-carbide particles with silica, and then when cool is milled down to 150 British Standard Mesh size. After being mixed with an organic binder the mixture is dried and then sifted through a sieve of 30 British Standard mesh on to a sieve of 60 British Standard mesh. The portion of the material retained on the latter seive is compacted in a press under 50,000 pounds per square inch into the annular pellet-form and sintered to a temperature of 1500.degree. C. in a non-oxidizing atmosphere.