Abstract: An aircraft has several ultrasonic phased arrays acoustically bonded to parts of its structure to be monitored. The arrays are energized to produce an ultrasonic beam that scans the structure in two planes. A monitor receives the output from the arrays produced by reflection of energy from discontinuities within the structure. When there is a change in these outputs, the monitor signals a pilot display unit and a flight control system such that the aircraft flight envelope can be restricted to minimize damage.

Abstract: An aircraft has several ultrasonic phased arrays acoustically bonded to parts of its structure to be monitored. The arrays are energized to produce an ultrasonic beam that scans the structure in two planes. A monitor receives the output from the arrays produced by reflection of energy from discontinuities within the structure. When there is a change in these outputs, the monitor signals a pilot display unit and a flight control system such that the aircraft flight envelope can be restricted to minimize damage.

Abstract: A current sensor assembly of planar form arranged for connection in series with an electrical circuit. The circuit includes a first and second conductor. The sensor assembly includes a first conductive member adapted to contact the second conductor in the circuit. A second conductive member is adapted to contact the second conductor in the circuit. A thin layer of conductive material is connected at one end to the first conductive member and at is other end to the second conductive member so that current flow in the circuit between the first and second conductors is via the thin layer. A support supports the thin layer along its entire length. At least a part of the support contacts the thin layer is electrically insulative. The thermal conductivity of the support is different at different points along the length of the layer so that heat disposition is different at the different points and hence the temperature rise caused by current flow through the layer is different.

Abstract: A rate sensor has a tine cut from a silicon substrate and resiliently mounted by two integral flexure beams. An electrostatic actuator drives the tine to vibrate in its plane. The tine supports two tunnel pick-offs in the form of spikes projecting from the tine, the tips of the spikes being positioned below a pick-off plate. In operation, the plate is moved down until it is closely spaced from the spikes and a tunneling current is produced. One spike is positioned below a recess so that there is a sharp fall in current when the spike passes beneath the recess, this signal being used to indicate the amplitude and frequency of vibration. The tunneling current output from the other spike indicates the separation from the plate. Rotation of the sensor about an axis y in the plane of vibration of the tine causes displacement of the tine at right angles, which is sensed by the tunnel pick-off.

Abstract: A gas discharge lamp has a tubular envelope containing tubular electrodes at opposite ends. An annular support member of a compressible ceramic fiber is supported in a groove around each electrode and is compressed against the inside surface of the envelope. Movement of the electrodes relative to the envelope is damped by the support member.

Abstract: An electrical switch has an evacuated housing with input and output terminals each connected to a respective group of metal tracks extending parallel and insulated from one another. A second silicon plate is cut to form several bridging elements, each having a metal layer on its upper and lower surface. Each bridging element extends transversely above tracks connected to different ones of the terminals. The housing is closed by a silicon cap having actuating tracks extending above the bridging elements, which form an electrostatic actuator with the metal layer on the upper surface of the bridging elements. When a voltage is applied to the electrostatic actuator, the bridging elements are driven down so that they contact tracks connected to different ones of the terminals and allow current to flow between them.

Abstract: A display has a matrix array of cells formed in a silicon plate and each containing a tungsten strip filament. The cells are filled with a halogen gas and are sealed by a double-glazed window with an infra-red reflecting filter to reflect heat back into the cell while allowing the transmission of visible radiation. The rear of the plate is treated to make it microporous and reduce its thermal conductivity.

Abstract: A single-axis servoed rate gyroscope has a sealed gimbal assembly that is mounted by bearings for angular displacement about a rotational axis, at right angles to the gyroscope spin axis. The gyroscope torquer comprises a circular, cylindrical coil mounted at the bottom of the gimbal assembly, coaxially of the spin axis and below the rotational axis. The coil extends in an annular gap formed between a cylindrical permanent magnet, mounted on the gyroscope base structure, and a part of the base structure which surrounds the magnet and which provides a magnetic return path. The magnet is polarized at right angles to the spin axis and the rotational axis, so that energization of the coil causes a restoring torque on the gimbal assembly about the rotational axis. The bearings are located in V-shape slots formed in the base structure surrounding the gimbal assembly.

Abstract: The inner unit of a gyroscope is of circular shape and is formed with an inclined outer edge at one end. The inner unit slides within an outer casing having a transverse end face at one end. An annular recess of triangular section is thereby defined between the inner unit and casing which receives a ring of resilient material. During assembly the inner unit is urged against the end of the casing, to compress the ring within the recess, by reducing pressure within the casing. The inner unit is held in position, with the ring compressed, by soldering an end plate to the casing. The pressure within the casing can then be returned to normal.

Abstract: A hydrodynamic gas-lubricated bearing comprises a rotor with a smooth bearing surface, and a fixed bearing plate with a grooved surface. The grooves are of spiral configuration being separated by lands, the top surface of each of which has a convex profile. The central portion of the surface is raised above the edges so that wedge-shape regions are formed between the surface of the rotor on both sides of the central portion. The surface of the fixed bearing plate may be formed with an overall convex surface. The grooved surface of the fixed bearing plate is made by forming a pattern of grooves in a smooth blank and subsequently rounding off the top surface of the lands by rotating the bearing plate under pressure against a soft abrasive cloth.

Abstract: Gyroscope apparatus includes a tubular rotor that is supported at opposite ends by bearings, such as a gas-lubricated bearing, for rotation about its axis. A gimbal ring encircles the rotor and is resiliently supported with the rotor, for angular displacement about an axis at right angles to the rotor axis, by a pair of flexure pivots located intermediate the ends of the rotor. An inertia ring is mounted concentrically with the gimbal ring by another pair of flexure pivots for angular displacement about an axis at right angles to the rotor axis and the axis of displacement of the gimbal ring. The major part of each flexure pivot is contained within the radial thickness of the gimbal ring. Displacement of the inertia ring is sensed by pick-offs the outputs of which are used to control the restoring torque applied by torquers located outwardly of the pick-offs.

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: 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.