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Aviation History
1963
1963 - 1707.PDF
518 FLIGHT International, 19 September 1%3 INDUSTRY international . . absorber travel on levered suspension systems. Others cover all intermediate requirements, including axle and tyre travel. Eureka enamelled wire is wound on a Tufnol tube reinforced by a central steel rod. There is an electrical connection each end, and a slider works between them to give a linear voltage change. All the instruments are connected to a multi channel cathode-ray oscillograph for record ing on photographic paper, the time marker lines being at 0.005sec intervals. When testing large multi-wheel bogie undercarriages the basic principles are the same, but the procedure and instrumenta tion are more complicated. Front and rear axles each have their own set of tyres, necessitating doubling up the tyre strikers and adding the bogie-beam movement. In some mechanisms each axle is supported on a separate cantilever beam and the balanc ing is carried through a third beam with a shock-absorber and dashpot mechanism interposed. The potentiometers have to be arranged accordingly. In some cases the acceleration at the axles has to be deter mined, which adds further complication. Obviously one six-channel recorder would be inadequate, so two are connected in parallel with one trace common to both. The records can thus be married, and eleven separate traces made simultaneously. Reverting to the simple unit, when side load has to be imposed (generally 0.25W) the wheel can be dropped on a 14° wedge, the contact surface being lubricated with a castor-base fluid which gives a very low coefficient of friction, especially on a brass surface. If there are two or more tyres on one axle, a special piece of apparatus is provided. This consists of a horizontal aluminium-alloy top plate and a steel base plate separated by two sets of wedges, giving a saw-tooth formation, and rollers between the inclined surfaces to give a very low coefficient of friction. When the tyres contact the horizontal top surface, which is grooved longitudinally to prevent slip, it moves sideways and thus applies the side load. Two of these "paral lel side wedges" are available. General dynamic considerations show that, in the case of a simple undercarriage, the total energy absorbed during the test is the falling weight times the total drop but the potential energy is equal to the kinetic WV2 energy on striking the ground, WH = v— but the mass has fallen through H + S where S is the compression of the tyre plus the axle movement, say Ht total, there- fore the mass to be dropped is W^y. This nt smaller mass is about 0.6W, but it varies according to the total closure of the unit. Energy is being put into the unit after the tyre has made contact with the ground, but this has a negligible effect on the simple type of unit and corrections can be made during the subsequent calculations. How ever, when bogie units are considered, the necessary corrections in the calculations become unmanageable. The full unit weight is dropped but, at the point of contact, an upward force equal to the unit weight is applied to the falling mass so that thereafter the undercarriage has to cope only with the stored energy in the mass. This is a true simulation. There are different ways of applying this upward force. None is particularly easy, because the device must have practically no inertia although quite large forces are involved (and these forces have to be varied to suit each design). The system employed at Arle Court comprises two upward- acting pneumatic cylinders connected at the moving end by a transom beam passing through a long, adjustable slotted member connected to the falling vertical post. At the top of the slot is a substantial steel pad, which makes contact with a rubber pad on the transom to avoid shock loading when the upward force comes into operation, i.e., when the first tyres make contact with the ground. Non-return valves with a controlled leak reduce the upward force during recoil. For spinning up the wheels, electrically driven drums are used. Each motor is mounted on a fork-lift truck, so that the height and position of the drums can be adjusted. The wheels are slightly over- speeded, and the trucks are then withdrawn. After a few seconds the wheels are running at the correct speed, checked by a strobo scope, and the quick-release mechanism is triggered. Commercial Map Display The Tactical Moving Map display developed by Com puting Devices of Canada Ltd under licence from MoA, based on an original RAE concept, is now being evaluated by A&AEE Boscombe Down and is offered for the first time for commercial sale in Britain by Computing Devices Co Ltd. The display employs a computer with adapters for either digital or analogue inputs to operate a projection system from cassettes of colour 35mm film covering an area 1,800 n.m. square. Tacan, VOR/DME, air data, Doppler or inertial inputs may be used, or the system can be coupled to the C.D.C. PHI. Map scales of half- or one- million can be selected and brightness controlled for ambient lighting between night and bright sunlight. The computer can accept speeds of up to 2,000kt, making it suitable for use in supersonic transports. Yet the whole display box measures only 6in x 6in x 11 Jin and weighs 151b. Track, bearing and range are continuously displayed in veeder counters beside the map picture, and the pilot can offset the map to look at any other part of the coverage. During this process, or while a new fix is inserted, memory maintains a running fix which reappears on selection of normal operation. The display can be track- or north-oriented. The TMMD can also be fitted to single-seat fighters or helicopters. World-wide coverage can be obtained by carrying additional cassettes of film. SARBE for the RAF A contract worth £100,000 has been placed with Burndept Electronics Ltd by the RAF for the supply of Search and Rescue Beacon Equipment (SARBE). This and other systems have Computing Devices of Canada's Tactical Moving Map Display now being tested by A&AEE Boscombe Down and offered for commercial sale in Britain by Computing Devices Co Ltd (see accompanying news item) been under evaluation for two years and the order suggests that the Burndept system will become standard. The Royal Navy has been using SARBE for some years. Burn dept is a member of the Royston Group. Both Services use the single-frequency UHF beacon transmitting on 243Mc/s but, while the RN has a speech facility, the RAF ver sion does not. The equipment now ordered is fully transistorized, and is in beacon and battery units together weighing 36oz. The transmission can be homed on with the aid of a simple homing attachment on the normal airborne communications radio, with which many Service aircraft of all types are already fitted. No special receiving equipment is needed. All Commonwealth countries are now evaluating SARBE and other trials are taking place for France, Italy, Israel, Norway and Denmark. SARBE can be fitted to all Martin-Baker ejection seats and has been accepted as standard equipment on the special clothing for TSR.2 crews. Belfast Contributors Apart from the airframe and powerplant manufacturers, many companies in the British aircraft industry have contributed to the Short Belfast, subject of a feature article on pages 499-508 of this issue. Contributions by some of these companies, named in alpha betical order, form the subjects of the bnet descriptions which follow. , AVICA EQUIPMENT LTD, Mark R°ad' Hemel Hempstead, Herts, have supply undercarriage hydraulic swivel joints, gun-
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