From: firstname.lastname@example.org (Terrell D. Drinkard) Organization: Boeing Commercial Airplane Group Date: 15 Apr 94 22:39:50 References: 1 Followups: 1
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In article <email@example.com>, EdwardZ450 <firstname.lastname@example.org> wrote: >Could someone provide me with the basic performance specs for the 757...i.e., >rate of climb, cruise, normal descent, etc...? Thanks very much. > > Ed in Maine > email@example.com I don't have a performance document at hand, and wouldn't be allowed to quote from it anyway :-), but I think I can remember enough general performance stuff to help a bit. The 757 is one of a number of twin engine airplanes that cruise at Mach 0.80, which is about 530 knots at cruise altitude (I think), or 610 mph for the rest of you. This is not the airplane's maximum speed, but rather its long range cruise Mach. A decrease in the airplane's speed would take it out of its most efficient operating condition and could actually cause the engines to burn more fuel. An increase in the speed would cause the drag to rise rapidly, causing a rapid increase in fuel burned. BTW, get used to Mach .80 as a cruise speed. That is getting to be a very common, almost a standard, cruise speed target for twins. The heavier three and four engine airplanes can cruise faster, but they were all designed some time ago - with one notable exception (the A340) which cruises at about Mach .82 as compared to the 747's cruise Mach of .855. Climb and descent rates are operational constraints usually. Climb can be limited by load and ambient conditions (heavy, high, and hot are badness). Descent is limited by flight idle thrust on the engines at one end and maximum design speed on the other. I hesitate to give a typical descent Mach number; we use a standard one, but I don't remember what it is offhand. My experiences with maximum climb rates is limited to 737s. I did a fix on an airplane and got to do a test flight to check it out. The airplane was empty, the deck angle was about 40 degrees, and the vertical speed indicator was pegged at about 6,000 fpm. The pilot said he could climb faster if he wanted to. :-) The pastry was good. (All test flights with customer pilots on them are catered.) -- Terry firstname.lastname@example.org "Anyone who thinks they can hold the company responsible for what I say has more lawyers than sense."