Re: Level Flight Deck revisited

From: (Paul Raveling)
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
Date:         24 Mar 94 14:01:30 PST
References:   1
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Walter Shepherd ( wrote:
: There have been a number of postings related to cabin attendants pushing
: carts up hill and whether or not it is efficient to fly airliners with a
: positive AOA on the fuselage.  Everyone seems to be assuming that the
: flight deck and the longitudinal axis of the fuselage are parallel... are
: they? does anyone out there know for sure?

	You may be misinterpreting the meaning of the term "deck angle".
	It really refers to the cabin floor, which could also be called
	the cabin deck.  The term "flight deck" is more akin to the
	nautical equivalent, "poop deck", as a label for "the place
	where we steer this sucker".  Of course "poop deck" the place
	originally was a true deck on galleons & such, but the name
	stuck longer than the separate structure did.

:  I have a dim distant
: recollection that in fact, they are not one and the same for the DC-10.  I
: recall hearing that substaintial structural weight was saved (remember the
: floor buckling accidents??) at the cost of tiring out the cabin attendants
: by having a 3 degree tilt on the flight deck.

	3 degrees is a common enough (cabin) deck angle in cruise.
	Most of the structural weight saving in question is common
	to all airliners I can think of and derives from having
	much more fuselage length forward of the center of lift
	than aft of it.  This makes the fuselage produce a net
	nose-up pitch moment; that reduces the downward (*) pitch
	moment that the tail must generate to maintain pitch

	(*) means that at aft CG's the tail may actually generate
	an upward pitch moment.  In this case the positive deck angle
	allows the tail to produce more lift than it would with
	no deck angle at all.

Paul Raveling