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Aviation History
1987
1987 - 1317.PDF
PROPULSION PW4000 "key to Pratt's commercial success" EAST HARTFORD The PW4000 has not been selling well in its early days, admits Pratt & Whitney's commercial engines presi dent, Larry Clarkson. The new big-thrust turbofan— follow-on to the successful JT9D series—came along a year later than General Elec- tric's CF6-802C, a derivative engine that to date has captured the lion's share of sales on the widebody twins, reports Julian Moxon. The PW4000's market lateness means that it has a long way to go before it catches up with the -80C2 on certification for extended- range operations (Erops), seen by many as the key to the widebody-twin market. Clarkson is undaunted. He comes up with a strong argu ment for the PW4000's future success: "We're ahead on 747-400 sales, and we fully expect further orders for that aircraft before the end of the year." The poor sales start is a "temporary aberration", he says. "GE was in the market earlier, but we have not lost any Pratt & Whitney custom ers. Because of the mainte nance investment, big-engine sales are somewhat divided along customer preference lines. Where we are now is somewhat dependent on who has placed orders. "Our forecast is that, from a dollar standpoint, 70 per cent of engine sales will be in the PW4000 class, and 50 per cent of that will be for twins. We've lost some Erops business, but I don't consider that to be critical. I believe the tables will turn on the Erops situ ation." Clarkson is certain that the PW4000, "which is the key to our commercial business," will leapfrog the -80C2, for several reasons. The PW4000's basic advantage is its core size, and low- maintenance design philos ophy, he says. "Our core is bigger than either the -80C2 or the RB.211-524D4D, which means that we can go to 65,0001b thrust without tear ing our engine apart. We use the same hardware, with only minor changes to the high- pressure turbine. GE can't make 65,0001b with the -80C2," he adds. Pratt & Whitney's Larry Clarkson believes that the PW4000 will turn the tables on General Electric's CF6-80C2 "We have a relatively calm, conservative growth programme for the PW4000," says Clarkson. "I disagree with my good friend Ralph Robins [of Rolls-Royce] that there will be a need for 70,0001b of thrust to power the coming twins. We're prepared to do it if we need to, but to go from 65,0001b to 70,0001b we'd need a new low spool, with a bigger fan. "70,0001b is a lot of thrust, and all three aircraft manu facturers admit there are some pretty big questions to be resolved—including the engine-out asymmetric thrust problem," he notes. Airbus Industrie is coming out on the A330 with a need for 64,0001b. What happens if the requirement grows? "Any decision would depend on the market. We'll work with the major aircraft manufacturers to provide engines for what ever they want to bring out. I believe there'll be derivatives of most current aircraft, including the A330, a possible MD-11 twin derivative, and maybe a 767-500," says Clarkson. Many of the PW4000's features are culled from the smaller PW2037 which powers the Boeing 757. It is well known that the all-new PW2037 suffered into-service reliability problems. ("The core has been extremely reliable," says Clarkson, "all of the problems were to do with accessory items, such as the gearbox.") Critics have said the PW4000 might suffer in the same way. Clarkson says this is not so. "There is a basic difference in design philosophy between the two engines. The priority for the PW2037 was low fuel burn, whereas in the PW4000 fuel burn was given equal status with maintenance cost. Our goal in the PW4000 was a 7 per cent, [s.f.c] reduction over the JT9D-7R4—-but we also said that maintenance cost would be 25 per cent less." "The point I'm making is that, if you want to talk about reliability, the PW4000 is doing very well. We have limited experience, but the real test is yet to come, when the 767-300ER starts flying at 60,0001b thrust". Clarkson admits that GE's -80C2 is currently setting very high reliability standards, "but it's operating derated, at 52,0001b thrust." Another important factor is Pratt & Whitney's consid erably longer operating experience with full authority digital electronic engine control (Fadec), first .on the PW2037, and now on the PW4000. "GE is still running with hydromechanical Con trols. All the new applications will need Fadec, not only because they are 'electronic' aircraft, but because big- thrust engines need the thrust-management protec tion that Fadec can give." Fadec will be introduced on the -80C2 in 1989, but Clarkson believes that GE will have to re-qualify their engine for Erops when this happens. "The FAA has made that very clear," he adds. Pratt & Whitney now has technical leadership on the International Aero Engines V.2500, "which is our entry into the bottom end of the big- fan market," says Clarkson. "I personally believe it will be the next CFM56, meaning that it's going to be a signifi cantly better engine." Clarkson is ready to admit that the V.2500's life depends on gaining another applica tion besides the A320, and the key to that, he says, is the continuing lack of airline interest in propfan-powered aircraft. "If there's a delay in the ultra-bypass engine in that thrust class, I think we'll see the V.2500 offered on another derivative Boeing 737, or a growth MD-91/92." Pratt & Whitney is not turning its back on propfans, says Clarkson. "My task is to have an engine ready when it is needed. We're working hard on the technology side of the equation. Our team [with Allison] is not designing a 'me too' engine. We've got to have something better than the [General Electric] UDF, or I won't do it." FLIGHT INTERNATIONAL, 1 August 1987 15
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