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