From: email@example.com (Derek H Cedillo) Organization: Massachusetts Institute of Technology Date: 11 Dec 92 00:38:19 PST References: 1 2 3 Followups: 1
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In article <airliners.1992.132@ohare.Chicago.COM> firstname.lastname@example.org (Gregory R. Travis) writes: [good outline of engine loading] >However, I am confused by Karl's statement that Lufthansa chose the A340 >over the A330 because of concerns that the twin-engined A330 would place more >stress on its two engines whereas the A340 would enjoy higher engine >reliability as its four engines loafed along. > >Since a twin engine jet is nominally overpowered compared to a four engine >jet, it should be able to operate, on aggregate, at a lower thrust setting >during takeoff or be operated at high thrust for a shorter overall climb. > >Since a four-engine jet has all four operating closer to the margin, in >normal operation, the engines should suffer from higher demands all around. I think the thing here, is that you are imagining two different engines entirely. This isnt exactly the case. I dont have thrust data handy, so I cant compare the A330 engine performance with the A340, but as a quick example, I'd like to point out that the A340, A320 and A321 all have the same GE engine spec (CFM56-5) while the A340 is a four engine plane and the A320 and 21 are two engine planes. Althought the 340 is definately bigger than the 320/1, I dont think the engine loading would be twice as much. (can someone come up with stats to prove or disprove please) Another look is the 767-200ER/300/300ER, MD-11 and 747-200/300/400 which can choose the GE CF6-80C2. All are relatively large planes, and they gradually increase in size, but is it huge enough to say the 747 is Twice as heavy/aero dyn loaded, etc, to require twice the thrust as the 767? Note that they have 2,3,4 engines respectively Again, I would appreciate any airframe data to support the weight/thrust/loading claim, or shoot me out of the sky as seen fit. Can someone help? Thanks, Derek ------------------------------- "He lived a life of going-to-do, and died with nothing done" -J. Albery In other words---JUST DO IT!