aerodynamic center


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aerodynamic center

[‚e·ro·dī′nam·ik ′sent·ər]
(aerospace engineering)
A point on a cross section of a wing or rotor blade through which the forces of drag and lift are acting and about which the pitching moment coefficient is practically constant.

aerodynamic center (AC)

aerodynamic center (AC)click for a larger image
Moment about the aerodynamic center is constant with angle of attack. Aerodynamic center does not move with angle of attack.
The aerodynamic center is a point on the wing chord that results in a constant moment when the wing angle of attack is changed. An AC lies approximately at the quarter-chord position at subsonic speeds and at approximately the half-chord position at supersonic speeds.