Re: airplane structural terms

Date:         13 Feb 99 02:25:51 
From:         "David Fielding" <dfield@epix.net>
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The chord of a wing refers to an imaginary line drawn through its airfoil
at any section, from the leading edge to the trailing edge. The mean chord
is an average of this line over the span of the wing. It is useful for
determining the angle of the wing in relationship to the rest of the plane,
and the air moving past it.

The percent of MAC refers to a distance from the leading edge of the wing;
often used to locate the center of gravity, or center of lift of a wing.
For instance, the lifting force of a given wing might center a third of the
way back from the leading edge, or 33% of Mean Aerodynamic Chord.

Wing incidence is the angle of the wing MAC in relation to the centerline
of the aircraft; it is a fixed figure, rivetted into the structure of the
plane (although a few planes were made with variable-incidence wings). A
separate matter is angle of attack, which is the angle between the MAC and
the relative wind, or air moving past the wing. Angle of attack is a
changing figure, based on speed, weight, control input, and other factors.

Hope this helps.

David Fielding
dfield@epix.net
Wish me luck on the Instrument written...