Re: T-tail

Date:         28 Sep 97 00:53:41 
From:         crosby@cpc.ee.up.ac.za (Charles Crosby)
Organization: University of Pretoria
References:   1 2 3
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k_ish (kenish@ix.netcom.com) wrote:
: JWizardC wrote:
: > A note and a question:
: >
: > Note: (E-flat) - Most folkes don't take into account that the horizontal
: > stabilizer also contributes lift to the aircraft. Granted, in most
: > cases that lift is negligable, but it is there. <snip>

: On an aircraft with conventional layout (i.e. not a canard design), the
: stabilizer generates lift in the downward direction.  So it *increases*
: the amount of lift the wing must generate; the stab has a negative
: contribution to lift.

The answer about whether or not a horisontal stabiliser has positive
or negative lift is not that simple.  In general, with a reasonable
CG position (say about 30% of the mean aerodynamic chord) and an airfoil
with a moderate negative pitching moment (ie. forward shift of the
center of pressure with increasing angle of attack) most aircraft will
have some lift on the stab at low speed and some downforce at high speed.
Using flaps and a far forward CG position will result in the lift on the
stabiliser becoming more negative.

Charles