Engine mounting

From:         raveling@Unify.com (Paul Raveling)
Organization: Unify Corporation (Sacramento)
Date:         26 Jan 93 23:47:08 PST
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	Another inquiry that I missed the first time around was this one
	by Daryl Morse:

> I have been told (by someone who had a lengthy career maintaining
> large military transport aircraft) that the DC-9 family of airliners
> exhibit a nose-down attitude under power. This supposed behaviour is
> attributed to the angle at which the engines are (or appear to be)
> canted.

	Actually all airliners, DC-9's included, are designed with
	a positive (nose-up) deck angle in level cruise.  This keeps
	drag low by producing a relatively smooth spanwise pressure
	distribution, without a big flow disturbance at the fuselage.


	All jets that I'm aware of with tail-mounted engines have
	the engines canted upward to some degree.  In airliners,
	it's true of everything from the Sud Caravelle through 727's
	and MD-80's.  In smaller jets, it's obvious on everything
	from ancient Sabreliners and Jetstars to late-model Gulfstream 4's.

	Unfortunately my recollection of this finer point of airliner
	design is too rusty to warrant responding.  Could someone
	who's more current in this area offer comments?


------------------
Paul Raveling
Raveling@Unify.com