Re: Boeing 757 Performance Specs?

From:         drinkard@bcstec.ca.boeing.com (Terrell D. Drinkard)
Organization: Boeing Commercial Airplane Group
Date:         15 Apr 94 22:39:50 
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Followups:    1
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In article <airliners.1994.1119@orchard.chicago.com>,
EdwardZ450 <edwardz450@aol.com> 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
>                                         edwardz450@aol.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
drinkard@bcstec.ca.boeing.com
"Anyone who thinks they can hold the company responsible for what I say has
more lawyers than sense."