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Aviation History
1987
1987 - 2236.PDF
PW4000 types and certification dates Aircraft A310-300 A300-600 A300-600ER 767-200ER 767-300ER 767-300 767-300ER (HGWT 747-400 MD-11 • High gross weight Note: The first number in each engine model Airbus/1, 747/2, MD-11/3) Engine model PW4152 PW4156 PW4158 PW4050 PW4056 PW4050 PW4060 PW4256 PW4360 represents the engine series the last two thrust (x 1,000lb). Aircraft certification June 1987 Nov 1988 Nov 1988 May 1988 March 1988 March 1988 2nd quarter 1988 4th quarter 1988 May 1990 the second the aircraft type (767/0, PVV415 PVV415 The P W4000 will be available in versions producing from 50,0001b to 58,0001b thrust to power a range of aircraft Engine orders/options Type A310-200ADV A310-300 A300-600 A300-600R A330 767-200ER 767-300 767-300ER MD-11 747-400 Total * Figures do not include GE PW4000 34/30 6/0 0/10 4/0 2/2 30/48 180/36 256/126 s latest order from Japan Ai CF6-80C2 12/10 88/8 30/10 52/2 14/8 30/20 34/16 48/26 93/63 144/76' 545/239 Lines for -80C2s to RB.211-524 22/30 88/136 110/166 power five 747-400S on firm order Sales figures reveal the PW4000 to be in a healthy position on the all-important MD-11 and 747-400, despite being, in effect, a year behind the CF6-80C2 responsibility for which has moved from Fiat back to Pratt & Whitney in the PW4000). Tad Domagala, Pratt & Whitney's vice- president for commercial product manage ment, puts the PW4000 design concept thus: "the high spool uses the design philosophy extracted from the PW2037, and the low spool uses that from the JT9D-7R4, which has been very good in service. The 2037 uses JT9D low-pressure experience as well, so you might say the whole engine is based on PW2037 experience". One of the most successful of the PW2037 hand-downs is the Hamilton Standard full-authority digital engine control (Fadec), which remains unique in airline service (GE plans to introduce Fadec in 1989). On the PW4000 the system controls more variables, as well as reducing fuel burn by an estimated 1 • 5 per cent, eliminating trim requirements, and providing a diagnostic capability. The real change in the PW4000 over previous designs comes as a result of the major effort Pratt & Whitney has made to reduce maintenance costs, primarily by means of a dramatic 54 per cent reduction in parts count, but also as a result of particular attention to durability. In the combustor, for example, Pratt & Whitney has introduced a machined ring burner which maintains better concen tricity, reducing thermal distortion, and hence stress, on the (single crystal) high-pressure (HP) turbine blades. Other durability improvements over the JT9D include stiffer engine cases, controlled-diffusion HP compressor blades (which have blunter, erosion- resisting leading edges) and relocation of the LP splitter further aft to improve dirt separation. The parts reduction is achieved in two ways—by increasing the efficiency of the aerodynamic components, which means there need be fewer of them, and through changes in manufacturing technology, which have enabled some large components to be produced as one part instead of as several smaller parts which subsequently have to be joined together. Most of the parts cut occurs in high- maintenance components, such as turbine vanes and blades, and the combustor. The PW4000 has 20 fewer major flanges than the JT9D, 30 per cent less tubes and brackets, and 2,600 fewer fasteners. There are 23 per cent fewer airfoils overall than in the JT9D-7R4. This includes a massive 43 per cent reduction in the high-pressure turbine (traditionally a high maintenance area) achieved by eliminating disc bolts, splining both discs on to the low-pressure (LP) shaft, and doubling up parts functions wherever possible. A 27 per cent blade reduction in the HP compressor, 11 per cent in the fan section, 9 per cent in the LP turbine, and 2 per cent in the booster completes the list. Pratt & Whitney bases its 25 per cent maintenance-cost reduction claim on what it calls the "maintenance material cost" of the top 15 high-value parts such as fan blades, outer and inner combustor liners, and turbine aerofoils. Particular attention has been paid to extending the life of these components, and of other life-limited parts such as turbine discs. "It is well recognised that Pratt & Whitney produces discs that have the longest life, because of our very soph isticated design system," says Domagala. "Our life prediction system has been accepted by the certification authorities," he adds, "which allows us to quote very long disc lives." Aerodynamic improvements over the JT9D include advances that came out of the Nasa-sponsored Energy Efficient Engine (E3) programme, in which GE and Pratt & Whitney built and tested a number of advanced components. The PW2037 benefited from E3 tech nology principally in the HP compressor, which has a higher blade loading than previous Pratt & Whitney turbofans. The PW4000 core retains the controlled diffusion compressor blading introduced on the PW2037 and, although it is less aggressive, still rotates some 25 per cent faster than the JT9D core, and has a 10 per cent higher pressure ratio. Pratt & Whitney has also introduced a new "thermatic rotor" HP compressor drum which reduces blade tip clearance by circulating compressor air internally to control disc expansion. Careful matching with the case design means that tip clear ances can be minimised passively, instead of by means of a more complex active clearance control system. Active clearance control is retained on low and high- pressure turbines, and is controlled by the Fadec, as on the PW2037. Service introduction of the PW4000 came last June on the first of Pan Am's 12 (firm) A310-300s. The engine is now flying on seven aircraft, including the first Sing apore Airlines A310-300. The engine has experienced no problems to date. "It's been a very good introduction", says Domagala. A ten-engine pacer programme keeps engine endurance hours ahead of airline service time. At the time of writing the PW4000 had built up around 7,750hr running time, including more than 21,000 operating cycles. As the table shows, Pratt & Whitney lags GE by a substantial margin on engine sales to date, principally because of the CF6-80C2's earlier in-service date. The GE engine has also built up a considerable lead in running time on the big twins, which means it is nearer to compliance with Federal Aviation Administration requirements for extended range oper ations (Erops). This is unlikely to affect long-term sales performance significantly, however, since the amount of engine/ airframe time required for Erops is consid erable, and the PW4000 will soon accumu late plenty of airframe time. Pratt & Whitney will not disclose its investment in the PW4000 (gone are the days of the "billion dollar baby" slogan coined for the PW2037), but says that it will be less than that of the PW2037 up to certification. Overall programme costs will be higher, though, because of the number of applications for which certifi cation is being sought. B 34 FLIGHT INTERNATIONAL, 31 October 1987
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