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Aviation History
1981
1981 - 0154.PDF
144 FLIGHT International, 17 January 1981 refined continually ever since and is now the most numerous of the big three turbofan engines. The first JT9D started ground-tests in December 1966. It was flown in a B-52E test-bed in June 1968 and the first Boeing 747 was powered by four 42,000(187kN)-thrust JT9D-1 engines on its maiden flight in Febru ary 1969. A remarkably short and intensive development programme was flown, and the JT9D certification target was met in May 1969. The Boeing 747 was due to enter service in December that year, but a one-month delay became necessary, mainly to alleviate engine problems. The 43,5001b(193.5kN) thrust expected from JT9D-3s in the first production deliveries was unobtainable, be cause of carcase distortion when the engine was attached to the wing pylon. There was also a significant shortfall in s.f.c, but aircraft were operated with these engines, without incident, and all delivered units were modified to JT9D-3A standard—restoring performance levels—before the end of 1970. This variant was soon followed into production by the JT9D-3W, a water-injection version which provided 45,0001b (202kN) thrust. The immense effort put into the JT9D programme can be judged from the fact that within two years some 900 engines were delivered and about two million flying hours were logged. By that time that 47,0001b (209kN)-thrust JT9D-7W was already in production. The first DC-10-20, powered by three 45,5001b (202-5kN)-thrust JT9D-15 engines, flew in February 1972. The type entered service in November that year, but only after having been re-designed DC-10-40. The in-service engine variant was the 48,5001b (216kN)-thrust JT9D-20, which used water- injection. New market forces spawned several engine variants in the late 1970s. An experimental high-pressure core had been run as early as 1971 under the designation JT9D-X, and was intended to provide the basis for a 55,000- 60,0001b(245-267kN) family of types. A version using this technology, the JT9D-S9A which was rated at 53,000Ib(246kN) thrust, powered an A300 in August 1978, and thereby broke the exclusivity of the CF6 on that type. The JT9D's grip on the Boeing 747 had been challenged by the RB.211-524 and CF6-50, so this bigger family of variants was also welcomed by 747 customers. The JT9D-7Q2 was certificated in June 1980 at 56,000(248kN)- thrust, the highest rating for any commercial turbofan at that time. Boeing's new 757 and 767 were attracting their first orders in late 1978, and set off a spate of bargain offerings from the big three engine companies. Boeing has remained aloof from the question of whose engines should power what, and the proliferation of engine/ Pratt & Whitney's JT9D-59 features a fan mounted accessory gearbox and has been chosen for the DC-10 and A300 airliner combinations is unprecedented. By December about a half of all 767 orders had been for P &W JT9D-powered variants. The latest engine, which is seen as the major sales version in the near future, is the 44,3001b (197kN)-thrust JT9D-7R, and it seems certain to be contested hotly by the CF6-80 as a Boeing 767 powerplant. The 48,0001b(214kN)- thrust JT9D-7R4 was certificated in October 1980, and in addition, variants of this power- plant will also be used in the A310 and Stretched Upper Deck 747. There are now 2,200 JT9Ds in service and over 35 million flying hours have been logged. Experience is currently accumulating at the rate of 428,000 hours a month. Pratt & Whitney JT10D (PW2037) Two-shaft turbofan. The JT10D was launched with an order by Delta Airlines in December 1980 for 60 twin-engined Boeing 757s. The engine is unique in being the only completely new commercial turbofan under development. Its main competitors are the CF6-32 and RB.211-535 'scaled-fan' deriva tives of existing larger engines, which although very good performers cannot hope to challenge the fuel efficiency of the JT10D. It is intriguing to see P&W waging a battle which has exactly the same elements as the arguments for and against the JT8D-2O0 series versus engines P&W now calls its JTIOD the PW2037 and has sized it to produce 37,0001b of thrust. Delta Air Lines has ordered 60 Boeing 757s powered by PW2037s, while American Airlines has chosen the engine without specifying the aircraft type such as CFM56 and RJ.500—but with the boot on the other foot. It is a collaborative programme, although P&W do the majority of the work with MTU taking an 11-2 per cent share and Fiat 4 per cent. Work started as long ago as Febru ary 1972 when a full-scale company rig was authorised, at that time aiming for a 26,7001b (119kN)-thrust engine which would have run in 1974. Rolls-Royce took a 34 per cent share in that programme, but as the market was redefined and the thrust requirement rose, the company withdrew to concentrate on its own competitive products. By 1979, when the RB.211-535 was launched on the back of initial Boeing 757 letters of intent, P&W were promoting the JT10D-136 as a competitive 36,0001b(160kN)-thrust engine offering a 10 per cent s.f.c. improve ment over 'scaled-fan' engines. Current pro posals are that the first JT-10D-136 should run in early 1982, that an engine should fly in a Boeing B-52 testbed about a year later, and that a 6,000hr 12-engine development programme should lead to certification of the type at the end of 1983. In December 1980 P&W announced their new series of designations for engines under development, and in future will refer to the JT10D as the PW2037. Rolls-Royce RB.211 Three-shaft turbofan. When selected to power the Lockheed TriStar in 1968 this engine put Rolls-Royce firmly in the big league of Western World aero-engine manufacturers. Today, almost ten years after development costs forced the original company into liquidation, the RB.211 programme still dominates UK aero-engine activities. Rolls-Royce had decided in the late 1960s that the most suitable configuration for future highly-efficient turbofan engines would be based on three shafts. Several development engines were run, and the major programme which emerged was the RB.207, an engine much larger than the concurrent RB.211. In 1968 the RB.211 took over the leading slot. It was chosen for the Lockheed TriStar and the first of 19 development engines ran at Derby in August 1968. The company dis closed an estimated £70 million development cost. In March 1970 an RB.211 was flown in a VC10 testbed, and development engines were emerging from the workshops at roughly monthly intervals. The company was opti-
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