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Aviation History
1989
1989 - 0683.PDF
Douglas studies V2500 as possible propfan replacement on MD-90 by John Bailey in Long Beach McDonnell Douglas is con sidering whether to offer the International Aero Engines V2500 powerplant as an alternative to ultra-high- bypass propfans on its proposed MD-90 series aircraft. Kim Still, vice-president and general manager of the MD-90 programme, says that such a decision would end plans for the UHB engine/airframe combination for the foreseeable future. "This is an either-or situation," he says. "It is not our intent to offer both engines, and, if we were to do that, it would be considerably down the line. Not much of what we are doing in devel oping this (V2500-powered) aeroplane reads across to the UHB". Douglas first studied the V2500/MD-90 combination more than three years ago, but decided to proceed with propfan development because of the greater fuel savings offered by UHB engines, according to Still. A modified MD-80 has already completed a limi ted demonstration program me with a proof-of-concept General Electric GE36 unduc- ted fan mounted on to the port pylon. The aircraft appeared at last year's Farnborough Air Show. Propfan flights The demonstrator is due to fly with the POC Pratt & Whitney/Allison geared prop- fan within the next week, and Douglas has been actively marketing MD-90s equipped with either engine. The company has not yet received the orders it needs to launch the programme formally, although at least three airlines (Delta, SAS, and Midway) have report edly agreed to convert later MD-80 options when MD-90s become available. Douglas is offering two ' versions, the 114-seat MD-91, and the 165-seat MD-92. At least two major carriers have now told Douglas that they would be more interested in ordering V2500-powered MD- 90s, prompting Douglas to study again the feasibility of the engine /airframe combination. Still tells Flight: "It is not clear to me whether these requests are motivated by the desire to have an alternative, or because there is something intrinsically better in their minds about the V2500 engine. "People are concerned about the technology risks with the UHB, but it's more a concern about the inevitable teething problems. Maybe it would be easier to do with an already certified engine. We are responding to that." Airlines have appeared reluctant to gamble on the propfan's greater fuel efficiency while oil prices remain low, but Still says: "How broadspread that is I don't know, and that's why we want to go out with the alternative. We are hopeful that if we treat the V2500 as an alternative, we will get a clear and crisp answer to that question." Discussions Still adds that no formal agree ment exists between the two companies, although he adds: "We are having ongoing discussions with IAE. We have told them that we are looking at their engine on our aeroplane, and we will share information with them when it becomes available. We will decide where we go from there if we can reach a satisfactory agreement with them on business issues." Although the study is still at a preliminary stage (Douglas has not given the proposed airframe / engine combination an alternative designation), Still says that his team will be ready to approach airlines with details in approximately two months. He says: "We won't reach a conclusion until we go out to the airlines. We will tell them what we think this aeroplane will do, what a rough-cut esti mate of the price will be, and whether it makes sense for their fleet planning, as opposed to the UHB." The turbofan-powered MD- 90s would still undergo substan tial airframe, systems, and avionics modifications com pared to the MD-80. Because of the increased weight of the rear- mounted engines, the horizon tal stabiliser will be increased in span, and made from composite materials. The internal struc ture of the vertical fin will also be altered to cope with the different loads. The most visible difference between the UHB- and V2500-powered versions, apart from the appearance of the engines themselves, would be in the engine mounts. Both UHB engines require enlarged pylons to accommodate the span of the propulsors, whereas the V2500 could be mounted on pylons similar to those used for the current Pratt & Whitney JT-8Ds which power the similar MD-80s. However, Still says: "It may look like the changes are modest, but thev are quite substantial, even for the V2500. The engines are just as heavy as the UHBs, and the thrust levels are virtually identical. Because we don t have quite the fuel effi ciencies [with the V2500], the aeroplane either does not have the range, or we have to increase the gross weight, which means strengthening the structure. It's not as easy as it might look." End-year launch If a launch decision was made by the end of this year, the V2500-powered MD-90 would be ready for deliveries in mid- 1993. Still says: "We could do it a little faster than the UHB, although I'm learning in my old age that aeroplanes need their gestation times". The company is still deciding where to locate the MD-90 assembly line, which will need different tool ing than the MD-80 line because the fuselages will be built in barrel sections, rather than as "clamshells". Still says: "We would like to do it here in Long Beach, but we continue to have very strong sales for the MD-80. In my view, we are going to have to convert later options for the MD-80s into the next version [MD-90s], and then we will have room for it here. If we don't, then the way we are building this aeroplane makes it amenable to doing it elsewhere." FLIGHT INTERNATIONAL, 18 March 1989 17
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