lift/drag ratio

lift/drag ratio (L/D)

The ratio of the coefficient of lift to the coefficient of drag of an airfoil at various angles of attack. It is a measure of the airfoil's efficiency. The angle of attack that gives the best lift-by-drag ratio is the most efficient angle of attack. In normal airfoils, this generally corresponds to 4°. Lift/drag = CL ½ρV2S/CD ½ρV2S=CL/CD