A Simple Method for Determining the Aerodynamic Center of an Airfoil

In presenting experimental data on the aerodynamic characteristics of airfoils, it is now generally accepted practice to refer the pitching moment coefficients to the aerodynamic center of the airfoil section. This point is defined as that about which the moment coefficient is constant throughout the range of angles of attack corresponding to the linear part of the lift curve. This paper presents a simple method for locating exactly the aerodynamic center of an airfoil directly from wind-tunnel test data, all that is required being the lift and drag characteristics and the moment of the air reaction referred to some known point.