Abstract: Electrodes of an electro-chemical machining tool are in the form of tubes which carry electrolyte to the surface of the article to be machined. The ends of the tubes adjacent the article are gripped between opposed clamping surfaces (13,14) of a block (10). One of those clamping surfaces 14 has a series of facets (15,16,17) with each facet inclined relative to the adjacent facet. The tubes are gripped between those facets (15,16,17) and serrations (18) in the opposed surface (13). This causes the tubes to have different orientations along the line of those tubes due to the relative inclination of the facets (15,16,17). This enables the tubes to conform to the trailing edge of e.g. a turbine blade.

Abstract: A compressor rotor structure for a gas turbine engine is made by linear friction bonding stub rooted blades and separate platform pieces, to lands between slots in a compressor disc periphery. These results an integral structure in which the periphery of the disc has had metal removed so as to form the slots and the disc is thus lightened, and the stub roots and platform pieces cooperate to form the airflow inner annulus wall.

Abstract: A fluid level monitor for monitoring the level of fluid in a vessel comprises an inverted U-shaped propagation member which allows the propagation of stress waves therethrough. A first limb of the propagation member is immersed in the fluid in the vessel and a second limb is positioned outside the vessel. A transmitter transducer and a receiver transducer are acoustically coupled to the second limb of the propagation member. The transducer transmit stress wave pulses into the propagation member, the stress wave pulses produce a diffuse stress wave field in the propagation member which is damped by any fluid contacting the first limb of the propagation member. The transducer detects the stress waves propagating in the propagation member and produces an electrical signal corresponding to the level of the diffuse stress wave field. An analyzer measures the decay rate of the diffuse stress wave field which is indicative of the level of fluid in the vessel contacting the propagation member.

Abstract: A fluid bearing assembly for a shaft comprising a plurality of rigid shells circumferentially spaced around the shaft. Each shell is provided with a profiled portion adjacent said shaft which in operation acts to provide an air cushion upon which the shaft rotates and a profiled end portion which prevents the shells moving radially inward beyond a predetermined point whilst allowing said shells to move radially outwardly.

Abstract: The stress-wave activity produced by the interaction between a writing instrument and a surface during the generation of a given piece of handwriting on the surface is detected and stored. The stress-wave activity produced by a subsequent generation of the given piece of handwriting is then compared with that produced by the initial piece of handwriting in order to determine whether the initial and subsequent handwriting pieces have a common author.

Abstract: An aerodynamic or hydrodynamic surface is provided with so-called "riblets" for reducing drag by modification of the turbulent boundary layer. The riblets comprises flow-aligned elongate projections of small height. In order to increase their effectiveness in reducing drag, just those parts of the riblets which extend above the height of the virtual surface--established by the riblets themselves due to their displacing the turbulent motion away from the real surface--exhibit an abrupt transition to a cusp-shaped profile which more effectively promotes very small scale flow-aligned vortices which drain energy from the larger drag-inducing low speed flow-aligned vortices or "streaks" in the boundary layer.

Abstract: In a gas turbine engine having a set of variable stator vanes, a vane actuator ring, and a set of actuator levers linking the vanes to the ring in a one-to-one relationship, an improved manner of linking the vanes to the ring comprises providing a lever of thin sheet material and clamping a trough-shaped end of the lever to a wedge-shaped end of vane stem so that the lever takes up the profile of the end of the stem.

Abstract: A machine tool produces a tapered slot by moving a tool laterally of the workpiece as well as directly into it. The lateral movement is shortened at the end of each half reciprocation, so as to form the taper. The shortened stroke is achieved by use of electronic circuitry in which transducers are utilized to indicate by voltage output, the magnitude of movement of the tool into the workpiece relative to the magnitude of the movement of the tool laterally thereof and on positive or negative numerical pair being noted, deriving a further signal therefrom and utilizing it to change the direction of reciprocation.

Abstract: Potentially very high power ratings can be achieved from rotary electrical generators in which permanent magnet rotor stages using modern high intensity magnetic materials, for example cobalt samarium or neodymium boron iron. The machine described comprises a plurality of axial field rotor stages each comprising a plurality of magnet segments arranged around a driven hub in a pre-stressed assembly in which encompassing hoop means exerts sufficient compressive stress on the magnets and hub assembly to counter centripetal forces generated by speeds of up to 100,000 rpm. Alternative methods of stressing the hoop means is described.

Abstract: An interturbine duct for interconnecting a gas turbine engine with a power turbine. The interturbine duct is of generally frusto-conical form and double skinned so that an annular cross-section volume is defined between the skins. Cooling air introduced in a generally tangential direction at the larger diameter extent of the duct follows a generally spiral path to the smaller diameter extent where it is exhausted into the efflux of the gas turbine engine. The spiral path of the cooling air ensures good heat transfer coefficients over both of the skins and obviates the need for baffles to direct the cooling air flow.

Abstract: A self acting air supported thrust bearing is formed viscokinetically between a static segmented thrust pad and a rotor connected to a shaft by a flexible link which allows the rotor to rotate about its own center of gravity. Thrust is transferred from the shaft to the rotor by a thrust disc acting as a diaphragm.As a result distortion of the rotor due to centrifugal and thrust forces which would cause the bearing to fail is reduced.

Abstract: To evaluate the working line characteristics of a compressor of a gas turbine engine, fuel is supplied from the gas turbine engine fuel supply to a fuel accumulator via a control valve. The control valve is closed when a predetermined quantity of fuel is in the fuel accumulator, and a three way valve is adjusted to allow high pressure fluid from a fluid cylinder into the accumulator to pressurize the fuel. The fuel is then supplied from the accumulator via the valve to a combustion chamber to be burnt to increase the pressure in the combustion chamber and hence the compressor. The pressure of the fuel supplied which causes a surge is indicative of the working line characteristics of the compressor. The pressure and quantity of fuel supplied are varied until a surge is produced.Reworking of compressors with reduced surge margin can be carried out. Enables evaluation to take place while the engine is fixed to an aircraft.

Abstract: A temperature indicating paint which is generally time independent comprises an organic resin, high temperature glass frit resin and one or more of the following elements; silver, gold, platinum, palladium, copper, nickel, chromium, titanium and silicon, dispersed in 10% to 70%, by weight, of a solvent. The paint is applied to a specimen by brushing or spraying and the specimen is then stoved for 5 minutes at between 750.degree. C. and 850.degree. C.

Abstract: A control system actively controls at least one troublesome mode of an unsteady motion phenomenon in turbomachinery in order to enable an increase in the operating range of the turbomachinery. For example, rotor blade flutter or rotating stall may be controlled in a turbocompressor. The control system has a control bandwidth which is at least partly coextensive with the bandwidth of the unsteady motion phenomenon and operates by passing sensor signals related to the unsteady motion phenomenon from a sensor array in the turbomachine to a mode filter which produces a signal or signals which are related to the troublesome mode or modes. The selected mode signals are amplified and phase-shifted by time-variable amounts so as to produce control signals having controlled amplitude and phase relationship to the troublesome mode.

Abstract: A stress wave load cell comprises a propagation member to which is acoustically coupled a transmitting transducer and a receiving transducer. Electrical pulses are supplied to the transducer form a pulse generator and the electrical pulses are converted into stress wave signals which propagate through the propagation member. The transducer detects the stress wave after propagation through the propagation member and supplies an electrical signal to a processor which gives a measure fo the load applied on the load cell.Damping members apply a damping load on the propagation member when a load is applied to the load cell. The damping members damp the propagation of the stress waves in the propagation member and the decay rate of the diffuse stress wave field set up in the propagation member is dependent upon the load applied on the load cell.

Abstract: A simple rotary bobweight overspeed governor mechanism is conveniently incorporated in a main fuel control system for a gas turbine aeroengine in order to prevent overspeeds of one and more of its compressor/turbine rotating spools. In order to prevent so-called "dormant" failures of the overspeed governor mechanism going undetected, the invention provides automatic checking of governor function by means of a microswitch linked to a main digital electronic controller of the fuel control system. The position of a spindle in the governor mechanism is proportional to the speed of the spool from which it is driven and each time the spindle is at the position which should correspond to a predetermined proportion of the maximum allowable spool speed, the microswitch is actuated and signals the electronic controller.

Abstract: In the operation of an electro chemical machine, damage can occur if there is direct electrical contact between the workpiece and the machine tool. Such contact causes a rise in machining current, and to detect this, signals representing the current are fed in a series of successive time periods to two peak detectors (34,36) alternately. The maximum value of the current in one period, detected by one peak detector (34,36), is compared by a differential amplifier (42) with the maximum value of the current detected by the other peak detector (34,36) in an immediately succeeding time period. If the difference, corresponding to a rise in current, exceeds a predetermined threshold value, determined by a window detector 46, a relay 48 is operated to disable the electro chemical machine.

Abstract: A combustion chamber for a gas turbine engine has a wall which is provided with rows of apertures. The apertures are arranged so that the axes of the apertures form an angle of between 25.degree. and 35.degree. with respect to the inner surface of the wall. The apertures have a first cylindircal portion and a second divergent portion to produce fan shaped apertures. An upstream portion of the wall has apertures arranged in axially spaced groups, each of which has three rows of apertures and a downstream portion of the wall has apertures arranged in axially spaced groups, each of which has two rows of apertures. The axes of adjacent apertures in each row are spaced apart by at least three times the diameter of the cylindrical portion. The apertures produce effective film cooling of the wall using less cooling air than conventional cooling rings. The apertures may be arranged locally to cope with hot spots.

Abstract: A fuel control system for a three spool gas turbine aeroengine has a fuel contorl unit incorporating an intermediate pressure spool overspeed limiter. A fuel control signal is produced which drives a fuel metering unit to meter the flow of fuel to the engine in accordance with control and sensor inputs as acted upon by predetermined control laws incorporated in the fuel control unit. The engine has variable inlet guide vanes (VIGV's) in one or more of its compressor stages and a safety problem arises in that if the VIGV's fail at an angle for low engine speed while the engine is accelerating to a high speed, the rotational speed of the intermediate pressure spool can increase very quickly. This can lead to overshooting of maximum acceptable levels of spool speed before known overspeed limiters have time to regain control.

Abstract: When a breakage occurs to the connecting links which connect a gas turbine engine to aircraft structure, the engine drops onto a fail/safe mounting. The drop is minimal in magnitude and the invention provides a visual means for appreciating that the drop and therefore the breakage, has occurred. Relative movement between engine and airframe frees a pop up member and enables it to project beyond the engine envelope, for observation by inspection.