Re: Rear engined aircraft. (727 DC9 MD80)

From:         limerock@aol.com (Limerock)
Organization: America Online, Inc. (1-800-827-6364)
Date:         02 Dec 94 02:48:59 
References:   1
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In article <airliners.1994.1723@ohare.Chicago.COM>, scottk1204@aol.com
(ScottK1204) writes:

For any airplane, the optimum engine orientation tends to be a little bit
nose up as the thrust generates a small lift increment Tsin(x), where x is
the angle of the thrust vector relative to the flight path, which slightly
reduces the amount of lift the wing must provide.  This reduces the wing's
drag.  Little forward thrust is lost, roughly T(cost(x)-1).  For aft
mounted engines, which tend to be above the c.g., the optimum upwards tilt
will be less than for wing mounted engines as they generate a downwards
pitching moment which must then be trimmed by the tail.

Hope this helps!