Abstract: A digital scan converter for use with a mobile (eg airborne) radar or other surveillance apparatus, having ground-stabilized storage allocations and apparatus-stabilized display, provisions for polar to cartesian coordinate transformation and scan to scan integration, and having a random-access store in which each store location is arranged to hold the digital data for a plurality of spots on the display.

Abstract: Adhesive compositions suitable for use at high temperatures which include the repeating unit ##STR1## wherein X is a divalent linking atom or group, advantageously, a direct link, --O--, --S--, --CO--, --SO.sub.2 --, --Ch.sub.2 --, or --(CF.sub.2).sub.n -- where n is an integer from two to eight inclusive and R represents divalent aromatic groups having the formulae: ##STR2## wherein Y is a divalent linking atom or group and is advantageously --O--, --S--, --CO--, --SO.sub.2 --, --CONH--, --CH.sub.2 --, or --(CF.sub.2).sub.n -- where n is an integer from two to eight inclusive and about 10 to 50 moles % of said divalent aromatic groups have at least one direct nuclear substituent selected from organocarbonylamino groups, preferably acylamino groups, a carboxylic acid group, and alkoxy-carbonyl groups, also includes a proportion of arsenic thioarsenate in order to improve the long term thermal stability of the adhesive composition.

Abstract: A microstrip antenna array takes the form of a feeder strip and a plurality of elements, each in the form of a strip attached to the feeder strip at one end and having an open-circuit termination at the other. Arrays are disclosed which use standing waves in the feeder strip and which use travelling waves. The elements can be of various widths to provide a modulated array and, in the case of a travelling wave array, to compensate for attenuation in the wave in the feeder strip. A frequency-swept array and a circularly polarized array are described.

Abstract: The present invention provides gas turbine reheat combustion apparatus for aircraft propulsion. The apparatus includes means for producing a flame stabilization zone in a stream of combustion supporting gas flowing in a duct, said stabilization zone having a recirculatory flow region therein, an injector for introducing a fluid comprising an inert diluent such as, for example, nitrogen, into the recirculatory flow region, and means for supplying the fluid to the injector.

Abstract: A liquid crystal device includes a sheet of plastic material having an open pore structure in which a liquid crystal material has been introduced. The liquid crystal material may be dichroic and contain one or more dyes which may be dichroic. The liquid crystal material may be nematic or cholesteric or a mixture of these two or a smectic material. Protective layers of plastic or glass may be arranged to enclose the sheet and the protective layer may carry electrodes. The liquid crystal may be applied to selected portions only of the sheet and the remaining parts of the sheet filled with a non-mesomorphic material.

Abstract: The disclosure of this invention pertains to a system for optimizing fuel consumption in an aircraft having two engines, wherein a computer is programmed to increase the fuel flow to the engine which, consequent upon a fuel flow perturbation, shows itself to be responsible for the greater acceleration of the aircraft. Direction changes resulting from unequal fuel flows to the engines are compensated for by automatic rudder control, and speed changes resulting from the fuel flow changes are compensated for by automatic speed control also acting on fuel flow, all whereby direction and speed of flight are maintained while fuel consumption is minimized.

Abstract: In night vision apparatus, a wide-angle view, and a narrow-angle but higher-resolution view, are observed simultaneously in superposed relationship to provide a composite view which is wide-angle, but has a higher-resolution part. Night vision goggles or binoculars have two optical channels, each with its objective lens system, image intensifier and eyepiece. One of the channels presents a wide-angle view of a scene to one eye and the other channel presents a higher-resolution view of a central portion of the scene to the other eye, both views having the same magnification. A degree of stereoscopy can be obtained in the central portion of the scene even though one eye is only receiving a low resolution view.

Abstract: A family of new compounds suitable for adding to cyanobiphenyls and other liquid crystal compounds to give mixtures having extended liquid crystal temperature ranges is characterised by the formula ##STR1## or, a simple substituted derivative thereof, where A is (CH.sub.2).sub.n, (CH.sub.2).sub.n O O(CH.sub.2).sub.n, n being an integer in the range 1-4, either X is hydrogen or an alkyl, alkoxy or alkanoyloxy group and Y is a cyano group or Y is hydrogen or an alkyl, alkoxy or alkanoyloxy group and X is a cyano group.The mixtures so produced may be used in known kinds of liquid crystal electro-optic devices.

Abstract: A fluid composition which is capable of exhibiting a substantial increase in apparent viscosity under the influence of an electric field and which is of the type wherein solid particles of a chemical substance are dispersed in an electrically non-conducting oleaginous vehicle, the chemical substance being a polyhydric alcohol which contains acid groups and which has an open structure wherein a significant amount of water is adsorbed.

Abstract: An aluminium alloy is provided which consists of 2 to 12% by weight of chromium, 0.2 to 3.0% by weight of iron, the balance being aluminium apart from minor proportions of impurities and incidental elements wherein most of the chromium is present as a metastable solution in the aluminium lattice which contains a precipitate phase of iron rich zones the major proportion of which have dimensions of 200A or less, the presence of large intermetallic particles, particularly at grain boundaries, being at a minimum. This alloy may be produced by an evaporation deposition process.

Abstract: A liquid crystal guest-host display device includes a dye dissolved in the liquid crystal material. The invention is characterized in that the dye comprises three colored dye compounds mixed together to provide gray in the absence of an applied electric field. The compounds may be Sudan Black, Sudan Red and .beta.-carotene. The liquid crystal material preferably includes at least one 4'-alkyl- or -alkoxy-4'-cyanobiphenyl compound.

Abstract: A directional coupler comprising a dielectric substrate having two opposing faces carrying a sheet electrode on one face and two comb like electrode structures on the other face. Each comb electrode has finger like electrodes projecting from a bus bar towards the other comb. Varying the length of finger electrodes and the amount of overlap varies the amount of signal power coupled between the two combs. Couplers may be arranged to couple up to 100% of signal power. When half signal power is coupled, a 3dB coupler, various microstrip circuits may be built e.g. balanced mixers, power dividers, or power combiners.

Abstract: An altimeter has a pointer which rotates clockwise once round a dial for each thousand unit (feet or meters) increase in altitude, the zero of the dial being in the nine o'clock position.Two digital displays are situated one above and one below the horizontal through the dial zero. When the pointer lies in the upper segment of the dial a reading is shown on the upper display and when the pointer lies in the lower segment of the dial a reading is shown on the lower display. When the pointer is in the region of the zero position (for example within 100 feet of the zero position) a reading is shown on both displays. The upper display then reads thousands corresponding to a pointer position above zero and the lower display reads thousands corresponding to a pointer position below zero (whether the pointer is above or below zero).

Abstract: Phase modulation apparatus particularly suitable for coherent radar applications wherein an interrupted carrier-wave is phase modulated according to a predetermined coded sequence. Apparatus comprises a carrier wave generator having an output for connection to an aerial, a delay line suitably coupled at one end to the output of the generator, and a modulation signal generator for controlling the reflecting actions of a reflector at the other end of the delay line so that signals travelling in the delay line are reflected with a phase-shift dependent on the signal produced by the modulation signal generator. The carrier-wave generator is switched on and off for transmit and receive periods respectively and when switched on its output signal will build up from noise levels injection-phase-locked to a delayed version of the previous transmitted signal, thus preserving phase coherence between successive transmitted signals.

Abstract: A method of producing a surface having a reduced reflectance to electromagnetic radiation in a predetermined wavelength band which comprises arranging on the surface a regular array of protuberances having a height which is not less than one third of the length of the longest wavelength in the band and at a spacing which is less than the length of the shortest wavelength of the band divided by the refractive index of the material of which the protuberances consist.

Abstract: An anti-oxidation coating, particularly for the exposed peripheral regions of graphite brake discs for aircraft, comprises a layer of silicon on the surface of the graphite, a layer of nickel overlying the silicon layer and a layer of chromium overlying the nickel layer. The silicon layer is suitably formed by flame-spraying followed by arc-melting, and the nickel and chromium layers by electroplating.

Abstract: A dynamically tuned gyroscope having a single gimbal has torsion flexures with torsional stiffnesses such that, at its tuned speed, the gyroscope is insensitive to angular vibration at a frequency of twice the rotor rotational speed. The drive shaft is connected to a first torsion flexure having an effective torsional stiffness K.sub.1 of zero, K.sub.1 being made zero by the use of ball races or pivots, by known mechanical methods such as over-center or toggle spring action, or by the use of magnetic or electrostatic systems. The rotor is connected to a second torsion flexure which is orthogonal to the first flexure. The second torsion flexure has a torsional stiffness K.sub.2 equal to 4w.sup.2 r.sub.3.sup.2 m.sub.3 where w is the tuned rotor speed, m.sub.3 is the component mass of a gimbal, on which the torsion flexures are mounted, on an axis through the center of gravity of the gimbal and normal to the plane of the gimbal, and r.sub.3 is the distance of the component mass m.sub.

Abstract: A color display system, for example an electronic data display or a color television system incorporates a display screen, for example a cathode ray tube phosphor, and at least one liquid crystal color filter. The screen emits light in the form of visual information in at least two colors, and the filter is controlled electrically in such a way that the colors transmitted by the screen may be switched according to input signal used to energize the screen.

Abstract: An aerofoil for use in transonic conditions is truncated aft of the point of maximum thickness and has a splitter extending downstream of the trailing edge and dividing the trailing edge into two sections. Each section has a concavely or a substantially parabollically contoured surface. The aerofoil comprises fans or outlets adjacent the downstream end of the splitter for inducing in each section a zone of recirculatory flow in the region bounded by the splitter, the surface and a boundary streamline of free stream airflow over the aerofoil, the recirculatory flow adjacent the splitter being upstream relative to the free stream airflow.

Abstract: 1. A process for the manufacture of a nitric ester by the nitration of an alcohol by a nitrating acid wherein the alcohol and the nitrating acid are reacted together in the presence of an inert highly halogenated hydrocarbon containing fluorine and which is a solvent for and has a boiling point which is between 0.degree. and 50.degree. C and which is below that of the nitric ester product whereby the temperature of the reaction mixture is limited to that of the boiling point of the solvent by evaporation of part of the solvent, separating out the solvent containing dissolved nitric ester from the reaction mixture, and evaporating the solvent to leave the nitric ester.