Oswald efficiency number
The Oswald efficiency, similar to the span efficiency, is a correction factor that represents the change in drag with lift of a three-dimensional wing or airplane, as compared with an ideal wing having the same aspect ratio and an elliptical lift distribution. == Definition == The Oswald efficiency is defined for the cases where the overall coefficient of drag of the wing or airplane has a constant+quadratic dependence on the aircraft lift coefficient C D = C D 0 + ( C L ) 2 π e 0 A R {\displaystyle C_{D}=C_{D_{0}}+{\frac {(C_{L})^{2}}{\pi e_{0}AR}}} where For conventional fixed-wing aircraft with moderate aspect ratio and sweep, Oswald efficiency number with wing flaps retracted is typically between 0.7 and 0.85.