Abstract: An electrical circuit has a substrate and a surface mount capacitor having a connector pad at each end. The substrate has two separate contact pads that are both soldered to the same connector pad on the capacitor. Two further contact pads on the substrate are soldered to the other connector pad on the capacitor. The contact pads on the substrate are connected to tracks that extend to plated-through holes and are electrically connected to one another at a point remote from the capacitor.

Abstract: A control system for an aircraft gas-turbine engine has positive and negative acceleration control units. Each control unit has a memory storing values of the maximum or minimum desired rate of change of fuel flow at different speeds beyond which surge or extinction will occur. The control units produce output signals, in accordance with the engine speed and acceleration, for controlling fuel flow so that it follows closely within the surge or extinction curves. The system also has amplitude gates that pass one or the other of these output signals to the engine if the speed of engine demanded by the pilot is such as to cause surge or extinction.

Abstract: A pressure transducer cross-check system (10) in which a pair of low precision pressure transducers (12, 14) which detect parameters related to each other in content are alternately periodically calibrated during the operation of the system by cross-checking by a solenoid actuated valve (18) which alternately connects one of the pair of low precision pressure transducers (12, 14) to its associated pressure input (20, 22) while connecting a common high precision pressure transducer (16) to the other of the related pressure parameter inputs (20, 22) for selectively alternately providing one of the pair of parameter input signals as a high precision pressure responsive input signal to the system controller on alternate cycles of the low precision pressure transducer pair in accordance with the cycling of the valve (18).

Abstract: A mach airspeed indicator capable of internally determining mach number and VMO from measured altitude and airspeed information directly. An internal microprocessor, capable of storing a plurality of selectable VMO curves and a table of mach number versus q.sub.c /P.sub.s, receives the measured altitude and airspeed information, determines VMO and mach number therefrom, and directly drives the VMO and mach number displays where q.sub.c represents the impact pressure and P.sub.s represents the static pressure. The measured altitude and airspeed signals are analog synchro signals. In order to drive the VMO display, the received analog altitude synchro signals are digitized in a synchro-to-digital converter comprising a single multiplying digital-to-analog converter for both sin .theta. and cos .theta. synchro functions, and fed to the microprocessor which verifies the appropriate VMO from the preselected VMO curve, and drives the VMO analog pointer via a stepper motor servo loop closed by the microprocessor.

Abstract: An aircraft head-up display system has a combiner comprising a block of transparent glass and a plate of transparent glass cemented to the rear of the block. The plate carries a reflection holographic element on its front surface abutting the block. Light from a display on the screen of a cathode-ray tube is projected into the combiner through one edge, at an acute angle onto its front face. The light is then reflected rearwardly through the holographic element to the rear face of the plate where it is reflected forwardly again. The holographic element is arranged such that some of the light incident on it from the successive reflections within the combiner is reflected at right angles to the surface of the plate, forwardly through the front face of the combiner and into the line-of-sight of the observer. Successive reflections cause light to emerge at several locations along the length of the combiner so as thereby to increase the field of view of the system.

Abstract: A connector for medico-surgical tubing has a plastics body with a male Luer tapered forward portion that is shaped for engagement with a coupling member having a cooperating Luer tapered bore. The body has a rear portion of prismatic shape and square cross-section that is embraced by a square aperture in a rear flange of a locking ring. The locking ring has a cylindrical portion which extends axially of the connector and which has an internal screw thread for engaging cooperating projections on the coupling member. The locking ring is thereby free to slide axially along the prismatic portion of the connector body but is prevented from rotation relative to it. The rear of the Luer tapered portion projects above the surface of the prismatic portion to limit forward displacement of the locking ring.

Abstract: A system for indicating the mass of fuel in several fuel tanks of an aircraft has a capacitive depth sensor and a permittivity cell located in each tank. Signals from the sensors and cells are supplied to a computing unit which computes the volume of fuel in each tank and its approximate density. The system has a densitometer and another permittivity cell which receive a sample of all the fuel supplied to the tanks, and supply output signals to the computing unit. The computing unit derives a correction factor by comparing an approximate value of density derived from the other permittivity cell with a more accurate measure of density derived from the densitometer. The correction factor is used to correct the approximate values of density derived from the permittivity cell in each tank.

Abstract: In a cathode-ray tube display system, signals defining the coordinates of the element of the screen on which the cathode-ray beam is incident in its raster scan are supplied to a comparator together with signals defining the coordinates of a series of points defining the image to be displayed. The comparator derives a brightness-weighting signal in respect of each element in accordance with the proximity of that element to those of the points defining the image within a predetermined proximity. The predetermined proximity may be equal to the separation between the points. The system also includes a store, brightness-weighting signals being added together in the store to produce a total signal for each element that is used to control bright-up of the element.

Abstract: A fuel-gauging system has a capacitive sensor that is mounted in a fuel tank and supplied with an alternating electric signal from an oscillator. The oscillator output is supplied to a diode-pump circuit that produces a D.C. voltage proportional to the product of the amplitude and the frequency of the oscillator output. The D.C. voltage is supplied to the input of a comparator that receives a constant voltage at its other input. The comparator produces a D.C. output voltage, dependent on the difference between its inputs, which is supplied to an input of the oscillator, the oscillator being arranged such that the amplitude of its output voltage is dependent upon the amplitude of the input voltage. In this way, the product of the amplitude and frequency of the oscillator output is maintained substantially constant.

Abstract: A hydraulic control system has two fluid supply circuits which control fluid pressure supplied to respective chambers of a fluid-controlled actuator, each chamber having an individual piston mounted on a common actuator rod. In normal operation, a major part of the pressure is supplied to the actuator by the first circuit in accordance with control signals derived from an external source. The second circuit supplies pressure to its respective chamber at a lower level in accordance with control signals derived from the differential pressure across the piston in that chamber, the pressure supplied by the second circuit acting to reduce the differential pressure across the piston. The system also includes a control unit that responds to malfunction of the first circuit or error in the control signals supplied to the first circuit, by disconnecting the first control circuit from control of the actuator, such as by equalizing pressure across the piston in the first chamber.

Abstract: A valve assembly comprises a resilient housing of plastic material and a valve element in the form of a unitary plastic body located within the housing. The body is closed at one end by a dish-shape portion having a circumferential lip which forms a seal with the housing. The body has a tongue formed in its wall, one end of the tongue being provided with an inwardly directed tooth. By inserting a tube or rod within the valve element to engage the tooth, the tongue can be displaced outwardly and the overlying part of the housing can thereby be distorted away from the lip to permit fluid flow through the housing. The valve assembly may be used to seal one end of the inflation line of a cuffed medico-surgical tube.

Abstract: An electrical indicator for providing a digital display representation of the value of an input variable has four display areas, each area being arranged to display an individual one of the digits of a four digit number representative of the value of the input variable. Each display area is in the form of a matrix array of light-emitting diodes. The indicator includes a computing unit which is arranged to energize those diodes making up each digit and, by varying the energization, to cause displacement of the least-significant digit within its display area upon change in value of the input variable. Digits within the other areas remain stationary until an adjacent less-significant digit is moved between `0` and `9` when the more-significant digit is displaced in synchronism with the less-significant digit. The computing unit includes a store which contains information as to which diodes should be energized to represent any particular digit.

Abstract: An electrical indicator has a consecutive series of light-emitting diodes which are arranged along a straight or curved reference scale. A limited region of the series, comprising several diodes, is energized and this illuminated region is displaced along the scale upon change in an electrical input variable supplied to the indicator such that the position of the region provides an analogue indication of the value of the input variable. To improve the appearance of the display and reduce power consumption, the brightness of the region varies along its length with one or both of the outermost diodes being energized at lower levels than another of the diodes. The indicator may include a shift register having a number of storage locations, each for storing signals representative of a corresponding one of the light-emitting diodes, the signals at these locations being displaced in accordance with change in value of the input variable.

Abstract: A control system for controlling displacement of the aerodynamic control-surfaces of an aircraft includes a first signal processor that is supplied with input signals from the pilot's control column and also with predominantly lower-frequency components of feedback signals derived in accordance with the actual position of the control surfaces. The first signal processor derives an intermediate signal from the input and feedback signal components by digital processing and supplies this intermediate signal to a second signal processor which also receives the predominantly higher-frequency components of the feedback signal. The second signal processor derives an output signal from the intermediate and feedback signal components by analogue processing and supplies this to an actuator for controlling displacement of the control-surfaces. The second signal processor may also receive additional feedback signals directly from the actuator.

Abstract: A probe assembly for measuring the speed of rotation of a gas-turbine engine compressor shaft has a sensor head mounted at one end of a tubular probe body by means of a bellows unit which permits limited axial displacement of the sensor head relative to the probe body. The sensor head has a sleeve sealed to its rear end, one end of the bellows unit being sealed to the sleeve and the other end being sealed to the probe body. The forward end of the probe body extends through the bellows unit and into the sleeve where it is resiliently coupled with the sensor head by a helical spring. Four outwardly inclined leaf springs are mounted on the end of the probe body within the sleeve and are resiliently urged against the inner surface of the sleeve so that they are free to slide over the surface of the sleeve while separation of the sensor head from the probe body is limited by engagement of the springs with an inwardly projecting lip on the sleeve.

Abstract: A display apparatus for displaying a plurality of physical parameters has a plurality of electrically-operable display regions which are to be operated in accordance with respective physical parameters. The display regions each comprise a plurality of display sections disposed in spaced array, an electrode which is common to all display sections in that display region, and a plurality of individual electrodes associated with individual and respective ones of the display sections in that display region. The electrodes of the said plurality of individual electrodes associated with one display region are coupled to respective ones of the said plurality of individual electrodes associated with another display region to form respective groups of electrodes.

Abstract: Display apparatus for displaying the magnitude of a physical parameter includes a plurality of display regions each of which contains a plurality of electrically-operable display sections. The display apparatus also includes an electric circuit means responsive to an electric signal representative of the said magnitude which is arranged to operate the display sections in a cyclic manner in accordance with that magnitude. To this end, the electric circuit means is arranged, during a first period of each cycle, to effect operation of any display regions in which all sections therein require to be operated and, during a second period of each cycle, to effect appropriate operation of any other display region in which only at least one of the display sections thereof require to be operated.

Abstract: A fibre-optic cable has a bundle of glass-fibre or silica-fibre strands extending along its length, each end of the fibre-bundle being sealed in a metal ferrule. A sheath of woven glass-fibre or silica-fibre extends about the fibre-bundle and is secured at each end to a respective ferrule in tension, such that the sheath is constricted onto the fibre-bundle along its length. The cable has an outer convoluted metal shell which is sealed at each end to a respective ferrule. A sleeve of elastic material extends around the fibre-bundle and the sheath, within the outer shell, and serves to support and cushion the fibre-bundle along its length. The sleeve may be of a woven fibre including glass-fibre or silica-fibre, and asbestos-fibre, or the sleeve may be of an elastomeric substance. A metal braid sleeve covers the outer surface of the convoluted metal shell. The cable may be included in a radiation pyrometer to transmit radiation to a radiation sensor.

Abstract: A terminal for an optical waveguide includes a connector having a longitudinal bore in which an end of an optical waveguide is to be anchored, lens means for transmitting light from one end of the waveguide and defining a recess including a focal point of the lens means, and a housing in which the connector and lens means are mounted. The terminal also includes an elongate optical member having first and second ends with respective end faces, the first end of the elongate optical member extending partially through the connector and being anchored therein, and the second end of the elongate optical member being mounted in the recess in the lens means with its end face disposed at the focal point of the lens means. The connector includes means for maintaining the first end of the optical member and an end of an optical waveguide in alignment with one another.

Abstract: An optical waveguide coupling comprises a connector having a longitudinal bore and a pair of optical waveguides, for example, optical fibres, whose ends are disposed in opposite ends of the longitudinal bore with the waveguide ends optically coupled to one another. The connector comprises a generally tubular body and a multiplicity of flexible elongate members mounted on the tubular body and extending longitudinally therethrough to define the longitudinal bore, the elongate members being spaced apart around the tubular body and being individually displaceable towards the tubular body. The flexible elongate members are displaced towards the tubular body by the ends of the optical waveguides and resiliently engage the ends of the optical waveguides to maintain them in alignment with one another.