Jet Engine Mounting Angle

From:         Tony Heatwole <HEATWOLE@LANDO.HNS.COM>
Date:         14 Jan 93 22:57:33 PST
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Daryl Morse brought up the question of jet engine mounting
angle in a previous article. This is something I've often
wondered about myself.  Most tail-mounted jet engines on
commercial airliners *appear* to slant downward toward the
rear. This is particularly noticable on the tail-mounted
engines of DC-10s and MD-11s. Here, presumably, downwash
from the wings isn't a mounting factor. 

What are the design tradeoffs in setting the mounting angle
for tail-mounted engines?  How do the effects of engine loss
and changes in engine thrust figure in this tradeoff? 

Tony Heatwole
Gaithersburg MD
heatwole@hns.com