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Aviation History
1964
1964 - 1019.PDF
574 FLIGHT International, 9 April 1964 On-board auxiliary power is provided by a Bristol Siddeley Cumulus a.p.u., which provides both shaft power and air bleed TSR.2 ... level surpassing anything achieved the other side of the Atlantic. In fact the TSR.2 concept has involved a thorough review of the design of radar, airframe structure, handling characteristics, auto- matic guidance and autostabilization. An intricate chain of equip- ment has had to be co-ordinated to work reliably under exceedingly stringent conditions; and every phase of flight and variation of mission must be taken into account. British Aircraft Corporation have approached this problem of co-ordination in a new way. In the United States, hitherto pre- eminent in the weapon system concept, it has usually been the prac- tice for the airframe contractor to subcontract out to an electronics manufacturer the responsibility of integrating the various electronic systems. But because this is only one stage in integration it has been necessary to have an airframe team working in parallel with the electronics contractor, and this has involved unnecessary duplica- tion. BAC have themselves tackled the problem as a whole, and by this means, they claim, they have cut development costs by more than half as compared with American philosophy. They outline the system, agree the specification with the subcontractors, and en- sure that the elements of the system work in accordance with requirements. This is done by carrying out detailed functioning tests in their laboratories on rigs representative of the aircraft. By this means problems of interference and cross-talk can be ironed out, and reliability of the system components can be ensured under every possible variation of working conditions. The rig tests also help tremendously in assessing the scale of the servicing problems, and in evolving checkout equipment suitable for RAF use. As a result of the complexity of the electronic subsystems, and the vast number of inputs and outputs that require checking, BAC have introduced "integrated systems testing" in order to make servicing a practical and efficient possibility. In other words, they have specified one piece of test equipment which uses the working system as a stimulus, and by running a test routine it will be possible to discriminate any faulty element in each system—which can then be withdrawn, replaced, and rechecked. All the major elements in the various subsystems are therefore fitted with pick-off points for automatic checkout. It is believed that this is the most comprehen- sive automatic checkout system yet developed, the integrated weapon system involving over 1,000 types of measurement. Chief source of electric power in TSR.2 is a pair of solid-rotor alternators, each of which is driven by a main engine through a Plessey constant-speed drive. The alternator is by Rotax, and has a rating of 30j55kVA Design of the automatic test equipment has been entrusted to Hawker Siddeley Dynamics Ltd, and it will be a development of TRACE (tape-controlled recording automatic checkout equipment), versions of which have already been supplied to the British and French Governments. The test routines are automatically switched through a taped programmed sequence to every subsystem element in turn. Any faulty element will cause a warning signal to operate, and will stop the test sequence. TRACE for TSR.2 will be mounted in a waterproof trailer designed for high-speed towing over un- prepared surfaces. Complete environmental testing will be carried out on the equipment to ensure that it cannot be penetrated by dust or water, and that it will operate efficiently in all climates. Altogether the demands of TSR.2 for field support promise to be remarkably light. Manual testing is also a requirement, and is catered for by using the same test pick-off points as are required for the automatic test equipment. These manual test sets are manufactured by the sub- contractors responsible for the systems themselves. Electrics and Electronics The electrical power system, for which Rotax are the principal subcontractors, has been tailored to the requirements of the electronics systems. The environmental tem- perature in which the generators have to operate—imposed by supersonic flight plus local engine temperatures—is well above the limits of previous designs. With the conventional salient-pole type of generator, mechanical difficulties are encountered under condi- tions of high temperature and vibration. Accordingly, solid-rotor air-cooled alternators, with no rotating windings, have been speci- fied for TSR.2. This is believed to be the first time that solid-rotor alternators have been used in a major power-generating system. Another unusual feature of the electrical system is the adoption of solid-state voltage regulators for high-speed response; these have been subcontracted by Rotax to Mullard Ltd. Each main solid-rotor alternator is driven by a Plessey constant- speed drive, and supplies 3O-55kVA output for the two main a.c. generating channels. A solid-rotor alternator, with its associated regulator, is driven by a Lucas hydraulic motor and provides what is a constant-frequency supply for a third emergency channel. Rotax, who have vast testing facilities, have been responsible for the co-ordination of the generating systems, and over 2,500 hours deve- lopment time has been spent in determining the various characteris- tics. In addition, the alternator and associated equipment have been subjected to environmental tests, including altitude and tem- perature. TSR.2's subsystems, and the way in which they are integrated, can well be related to P. A. Hearne's "Digital Computers for Air- craft" in this journal's February 20 issue. A diagram in that issue illustrated a typical on-line central computing system for a military aircraft. In TSR.2, the central digital computing system is supplied by Elliott Flight Automation, Mr Hearne's company. Quoting from his article—with interpolations—"The sensor group, consisting of inertial platform (Ferranti), forward-looking radar (Ferranti), sideways-looking radar (EMI), Doppler (Decca) and air-data system (Smiths) provide 'raw' signals ... to the computer. The computer processes these signals to provide outputs for the display of position and steering information (Smiths, Rank-Cintel head-up display) and also for the direct control of the aircraft through the autopilot (Elliott Flight Automation) and for the preparation and release of weapons." While the computing system can be programmed by means of previously-prepared magnetic tapes for a very wide range of military missions, the crew are not, in fact, immutably tied down to a pre- programmed flight. Should local or tactical considerations demand a change of in-flight plan, the crew can feed in the necessary infor- mation and the pilot can at any time take charge manually. Out- puts provided by the Smiths air-data computer include true air- speed, Mach number, rate of climb, altitude, indicated airspeed, dynamic pressure, static pressure, stagnation temperature and rate of change of height. Corrections for pressure error and Mach number are incorporated. Ferranti's forward-looking radar provides terrain-following signals to allow the aircraft to approach its target at very low level, safe from detection by enemy ground radars. Ferranti have also provided the stable platform used in the Doppler/inertial navigation system, a three-gyro and four-gimbal system, fully manoeuvrable. The Doppler radar, supplied by Decca Radar Ltd, measures ground speed and drift angle to a very high degree of accuracy throughout the complete flight envelope, and under extremely
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