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Aviation History
1973
1973 - 2117.PDF
250 CF6-POWERED 747 continued from page 245 FLIGHT International, 9 August 1973 (CF6-50O ENGINES) Maximum taxi weight Maximum brake-release weight Maximum landing weight Maximum zero-fuel weight Operator's empty weight Maximum structural payload Cargo volume Main deck Lower deck Fuel capacity 747-300B 803,0001b 795,0001b 564,0001b 526,5001b 369,9001b* 156,6001b — 6,190 cu ft 50,770 US gal 747-300C All-passenger 803,000lb 795,000lb 630,000lb 590,000lb 382,000lb* 208,000lb — 5,990 cu ft 50,770 US gal All-cargo 803,000lb 795,000lb 630,000lb 590,000lb 341,6561b** 248,3441b 27,635 cu ft 5,990 cu ft 50,770 US gal 747-300F • 803,0001b 795,0001b 630,0001b 590,0001b 322,0561b** 267,944lbf 27,635 cu ft 5,990 cu ft 50,770 US gal -- uoes noi inciuae pane f Includes pallet weights. there is not much of a market for aircraft with extreme range. Given a substantial fuselage stretch of some form— probably with a double-deck cabin—the CF6-50-powered 747 could easily meet possible mid- or late-1980s require ments for a 600- to 850-seat short-range airbus, even without the higher-rated engines. What is perhaps more significant is that a 747 freed from volumetric limitations could fulfil one of the prime needs identified by British Airways for the latter 1980s—a 600-plus-seater for 3,000- mile to 3,500-mile ranges, and a 450- to 600-seater to go a few hundred miles further. British Airways thinks that its requirements fairly accurately represent a microcosm of the world's transport aircraft requirements. The CF6 today General Electric recently announced that the CF6-50E for the 747-300 should be certificated by the FAA in January 1974, considerably earlier than originally planned. It will be available one month later, rated at 52,5001b, 234kN of thrust to ISA+10°C (77°F), although the 747-300 itself is unlikely to be available for airline deliveries until early 1975. The -50 on the bench at the General Electric factory at * 385 passengers (32 first-class/337 tourist, plus 16 first-class on upper deck). •• Does not include pallet tare weights (16.6441b). is pallet weiahts. Evendale, Ohio, is now past the 7,000-cycles mark. The highest-cycle in-service engine has completed more than 1,300 flights. Hours run are more than 2,100 on the test engine and more than 1,500 in service, respectively. More than 100 McDonnell Douglas DC-lOs are now in service, making more than 300 flights a day, and all air lines but one have versions with CF6 powerplants. Engine hours are building up on the -50 engine and the smaller -6 combined at over 6,000 per day at present. Typical aircraft utilisation is between lOhr and 13hr (Swissair) for the DC-10-30s on international services, using the -50 power- plant. The in-flight engine-caused shut-down rate is about 0 12/l,000hr and removal rate 0-33. Before launching the CF6 family of turbofans, General Electric had accumulated only ten million hours of airline engine experience with its CJ805 jet and aft-fan engines, but already the CF6-6 has passed the 12 million hr mark and more than 450 CF6s have left the GE plant at Even- dale. About a third of them have been -50s for long-range DC-10-30S and A300Bs. Orders for DC-lOs and A300Bs combined stand at well over 200, so the known requirement for the CF6 is approximately 75 per cent of the 1,300 for the Pratt & Whitney JT9D which powers the 233 747s so far sold. GE in general • ANDY HOFTON reports from Evendale T HREE PRIMARY REASONS are given by John Pirtle, general.manager of the CF6-50 projects department, to explain why the CF6 is the only high-bypass-ratio turbofan to be adopted for twin-, three- and four-engined wide-bodied transports. The GE engine, says Pirtle, has a lower specific weight, offers more thrust and has a significantly lower specific fuel consumption than either of its rivals. He ascribes the s.f.c. advantage to meticulous attention to cycle efficiency. While admitting that the CF6 has perhaps two more compressor stages than might be included on a new design, he suggests that this is the key to overall efficiency and a good s.f.c—it being a fairly straightforward task to design a fan of above-average performance. He says that the CF6 has exceptionally wide fan- and compressor-stall margins. Deliveries have always been ahead of schedule, performance has always been better than specification and the problem with C-sump cracking was sorted out without interrupting airline schedules. About 2801b, 128kg of plastics, representing some 4 per cent of engine weight, is used on the CF6. These com ponents provide a 30 per cent saving in weight and 50 per cent saving in cost compared with metallic alternatives. The number of seals, spacers and the amount of sound- suppression material are apparent from Frank Munger's accompanying drawing. Only 1861b, 85kg of plastics was used on the TF39. Although General Electric has carried out extensive tests with fibre-reinforced fan blades, Pirtle says that the technology for plastic fan blades is not yet available and the problems of impact damage and rairi erosion still have to be overcome. Engineers from both General Electric and Pratt & Whitney visited Rolls-Royce at Derby following the second incident of RB.211 fan failure. Pirtle says that the cause
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