Date: 06 Jul 98 03:24:41 From: JF Mezei <email@example.com> References: 1 2 3 Followups: 1
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Stephen H. Westin wrote: > I think you're leaving out another factor: efficiency. I believe > bigger engines have lower specific fuel consumption. So an aircraft > with four engines, each of 50,000-lb thrust, will always be less > economical than a similar one with two 100,000-lb thrust engines, > other factors being equal. The question should be: If a 4 engined plane has 4 50k lb-thrust engines (200k total), how much thrust would a comparable twin have ? Since they must be able to survive on a single engine after having reached V2 (or is it V1 ?) during takeoff, surely there must have to be some "spare" thrust into each of the 2 engines ? So, if a twin engine aircraft must have spare capacity in its engines, how much does that spare capacity cost to carry/maintain/build compared to the cost of 4 smaller engines which do no stretch materials to their limit ? Is it not logical to say that the 777's engines, being state of the art and challenging engineers and materials to their limits, would cost more to build/research than building smaller engines for whom today's materials represent little or no challenge ? I am not familiar with jet engine prices (they don't carry them in stock at the local supermarket:-). It would be interesting to see a comparison of *purchase* price for 4 A340 class engines compared to the price for 2 777 class engines.