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Aviation History
1973
1973 - 1099.PDF
RIGHT International, 26 April 1973 Adour in final assembly at Derby later trials, which have been conducted at Warton, Bedford, Boscombe Down, Villacoublay, Cazaux and Istres. However following the incident to S.06, engines delivered for flight test have been reworked, and are now flying with a higher modification standard. One of the objectives of the continuing development programme is to demonstrate that the modular build-up of components (there are eleven separate assemblies) can be used effectively and without loss of performance under operational conditions. A modification of great significance was the adoption in 1970 of a modulated afterburning system. This scheme, known as PTR (Part Throttle Reheat) was proposed by RRTI about 1967, but was not at that time accepted by the two Governments on account of cost. However the need for a more precise control of engine power showed up early in the Jaguar flight-test programme under certain conditions. On final approach with both engines running full glides-path control is achieved by variation of the available dry thrust. However on a single-engine approach the power setting required can fall between maximum dry and some percent age of reheat, depending on weight. The specification for the initial standard of engine defined a throttle/thrust rela tionship such that a jump of about 1,6001b thrust occurred on selection of reheat, so that precise control of the glide path over a wide range of approach conditions was difficult. The French Navy, in particular, was concerned for the safety of its carrier operations with the maritime Jaguar. Accordingly the afterburner was modified to accom modate the PTR mode of operation. This allows the engine speed to be varied from about 70 per cent r.p.m. to maxi mum r.p.m. with reheat lit. By this means engine thrust may be augmented from quite a small throttle opening in such a way that there is no sudden jump in thrust when the throttle goes through the afterburner gate. PTR for each engine can be selected, by means of a single switch, over a wide range of throttle settings. Alternatively, normal afterburner performance, beginning at 100 per cent dry thrust, is still available for combat or where the sudden jump in thrust is acceptable. Within the range of opera tion, PTR is instantaneously available on selection, and 651 builds up from the minimum engine speed at which PTR is available to maximum reheat in 3sec, in contrast to the 7sec-8sec required in the normal mode. The engine for Japan's T.2 trainer has the same main components and ratings as that for the Jaguar, but there are a number of installation differences. The 12 engines already delivered to the Japanese Defence Agency, the final one in March last year, bear the designation Adour Mk 801X. The definitive engine will have part-throttle reheat and double afterburner catalyst. Parallel developments of non-reheated Adours are in hand. The first version is the RT.172-06 for the subsonic HS.1182 strike-trainer, in which more than 95 per cent of the components are common to the Mk 102 powerplant for the Jaguar. There is a slightly different matching of the low-pressure compressor working conditions, as a result of the lower minimum and cruise speed of the HSA aero plane. Two bench engines, designated Mk 151X, have been built and are on test, and twelve development and flight units are on order. Two hydraulic pumps, for the duplicated hydraulic system, are fitted in place of the single installation on each of the Jaguar's two engines, and the absence of an afterburner fuel control system allows a better layout for some of the "plumbing." For this single-engined aeroplane a new engine-control amplifier is required as a safeguard against individual component failure. The main parameters which decide en gine fuel flow on the Adour are exhaust gas temperature and low-pressure shaft speed, and the amplifier uses these parameters to control fuel flow. Rolls-Royce Turbomeca has proposed a three-stage im provement programme for the basic Mk 102 engine. The first step will be an increase in turbine inlet tem perature by 40°C-50°C to produce about 7 per cent more thrust. This would necessitate additional cooling air The second would be the adoption of a larger afterburner to give a lower Mach number in the jet pipe. In the Jaguar installation the tunnel length could be increased by about 9in, and the diameter increased by 3in, without the neces sity for significant airframe modifications. This would con fer a further 20 per cent increase. A scheme for a larger afterburner for the Jaguar has been put to the joint indus trial company Sepecat and to the two-Government manage ment organisation. The third proposal is for a 5 per cent increase in mass- flow, made possible by a small increase in the diameter of the low-pressure compressor. Coupled with the changes listed above, this would result in power increases in excess of 30 per cent at the appropriate flight conditions. A civil version of the Adour is proposed for corporate- aircraft and feeder-liner use, based firmly on the existing engine to capitalise as far as possible on experience gained with the military versions. In its present form, says Rolls- Royce, it will satisfy the noise levels stipulated by FAR Part 36, and hush-kits to provide a further 4PNdB-5PNdB can be offered. Changes from the unreheated, military-standard power- plant will be restricted to those necessary to accommodate the engine in pods rather than tunnels, for example, different mounting arrangements and modified gearbox drives. A typical pod would be about 12ft long, 42-5in deep and 35in wide. Rolls-Royce Turbomeca estimates that prototype engines could be made available about 30 months from a decision to go ahead, and production release could follow between six months and a year later. The conservative engineering built in to satisfy the requirement for ruggedness (particularly for the French Navy) should confer a good TBO for commercial application and the modular construction will enable "on condition" assemblies to be replaced quickly. This version is offered with a take-off thrust level of 5,0001b. The relatively low pressure ratio of 10.45. ensures a low smoke level, an im portant consideration in the context of the tough regula tions for turbine engines proposed by America's Environ mental Protection Agency. Growth versions of the unreheated engines are proposed with thrust increase up to 20 per cent. These would employ similar steps to those proposed for the reheated engine, and could also read across to commercial applications. •
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