Re: Do DC-9s exhibit a nose-down attitude under power?

From:         weiss@turing.SEAS.UCLA.EDU (Michael Weiss)
Organization: SEASnet, University of California, Los Angeles
Date:         20 Jan 93 02:39:39 PST
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In article <airliners.1993.43@ohare.Chicago.COM> morse@mprgate.mpr.ca (Daryl Morse) writes:
>If I had to guess, I'd say the inlets are optimized
>for cruise downwash conditions with the landing/takeoff downwash falling
>within the design tolerances.

It should also be noted that the fuselage during taxi (and the takeoff/landing
rolls) actually is pitched down, and the engines themselves are close to
horizontal.  This seems to match the desire to not turn the air in the inlet,
and still manages to handle this under nearly every condition.

As an aside, it is often desireable to have a force pushing the nose down in
an aircraft, as this prevents pitch instability.  Pitch instability is the
condition where there is a natural tendency to pitch up, which causes a natural
inclination to stall the wings...bad idea.  Hence the desire to prevent that
from happening unless the pilot specifically "instructs" the aircraft to do
it.  It is unlikely, however, that this is the reason for the particular
engine orientation on the DC-9.
-- 
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-  Michael  weiss@seas.ucla.edu   |  School of Engineering & Applied Science  -
-   Weiss   izzydp5@oac.ucla.edu  |   University of California, Los Angeles   -
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