Wing Twist

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  Wing twist is of two types named as geometric twist and aerodynamic twist:- Geometric Twist Different angles of attack at wing root and tip. Wash in Tip chord has a higher angle of attack than that of root chord. Wash out Angle of attack at tip is lower than that at wing root. It is useful in reducing tip vortices. Aerodynamic Twist Difference between zero-lift lines of airfoils at wing root and near the tip. Airfoils at root and near the tip have different zero lift angles of attack.
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Aerodynamic Center

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Aerodynamic Center

The aerodynamic center is the point on the chord at which the pitching moment coefficient does not vary with lift coefficient, i.e. angle of attack. It is the point where the aerodynamic forces are supposed to act, a fixed location on the chord.


Lift and drag forces can be applied at a single point, where they exert zero torque, at center of pressure but it moves with angle of attack as pressure distribution changes thus, makes the aerodynamic analysis complex.


For most low speed airfoils aerodynamic center lies at (1/4) of chord back from the leading edge in supersonic airfoils it is nearer to the (1/2) chord location.

In case of symmetric airfoils the aerodynamic moment about ac is zero for all angles of attack. With camber, the moment is non-zero and constant for thin airfoils. For a positive camber airfoil the moment is negative and results in the counter-clockwise rotation of the airfoil.






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