Pitching moment

However, as angle of attack changes on a cambered airfoil, there is movement of the center of pressure forward and aft.

One of the remarkable properties of a cambered airfoil is that, even though the center of pressure moves forward and aft, if the lift is imagined to act at a point called the aerodynamic center, the moment of the lift force changes in proportion to the square of the airspeed.

The combination of the two concepts of aerodynamic center and pitching moment coefficient make it relatively simple to analyse some of the flight characteristics of an aircraft.

The pitching moment coefficient is important in the study of the longitudinal static stability of aircraft and missiles.

is defined as follows[1]: Section 5.4 where M is the pitching moment, q is the dynamic pressure, S is the wing area, and c is the length of the chord of the airfoil.

The aerodynamic center is defined to be the point on the chord line of the airfoil at which the pitching moment coefficient does not vary with angle of attack,[1]: Section 5.10  or at least does not vary significantly over the operating range of angle of attack of the airfoil.