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| Re: Boeing jet to break distance record (74231) | |||
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Re: Boeing jet to break distance record |
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Posted by WillD on Thu Nov 10 12:58:05 2005, in response to Re: Boeing jet to break distance record, posted by RonInBayside on Thu Nov 10 11:27:35 2005. I believe a bypass turbofan's effectiveness becomes greater with an increasing bypass ratio and decreasing pressure at the blade tip of the fan. It was from this theory that the Propfan was developed, the basic idea being that the bypass ratio would be much greater for an unshrouded fan than for one within the engine nacelle as on a conventional turbofan. For a while both Boeing and McDonnell Douglas were prepared to offer propfans on their next offering of small to medium sized airliners, MDC was planning on the MD-90 and 95 using them while Boeing was devising a brand new airliner with tail mounted engines they dubbed the 7J7. Both engines for the new airliners had more than their fair share of teething problems and with the sudden glut of fuel prices in the mid 1980s the program was scrapped. Once again a program for saving fuel begun in the 1970s was scrapped in the 1980s due to fuel prices dropping, much to our great sadness in these days of rising fuel prices.In the end the failure of the propfan program may have lead to Airbus getting it's foot truely in the door of the US airliner market. The airlines at the time were getting anxious to replace their aging DC9s and 737-200s with something newer, or at least supplement their old aircraft with something a bit more modern. Because Boeing and MDC had their light to medium capacity airliner expenditures taken over by their propfan airliner programs, they were in no position to offer an improved DC9 or 737. Into this gap stepped Airbus, with their A320, which airlines had been gunshy about with it's new fly-by-wire system and somewhat controversial V2500 engines. Left with no choices from Boeing or MDC the airlines pretty much had to purchase A320s or face mass obsolesence of their turbojet powered 737-200s and DC9s in the coming years with no suitable replacement. Both manufacturers tried to hold off the airline's Airbus purchases with promises of great fuel savings from the propfanliners, but with fuel prices then falling it was a hollow argument to airliners looking for much more than either company was offering. In the end both Boeing and MDC retreated from propfans, going instead to far more conventional designs. Boeing simply upgraded the 737 series with CFM56 turbofan engines and an improved cockpit producing the -300, the lengthened -400, and the shortened -500. McDonnell Douglas scrapped their propfan program and the MD90 was equipped with the same turbofans which the prior MD80 had recieved. |
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