... In aviation it is usually more convenient to consider the motion of air over a wing or over a propeller blade in their own frames of reference. This lesson examines swept-back airliner wings (also at swept-forward and swiveled wings), and at the loss of propeller efficiency when the airplane gains forward speed. ... 22c " Airplane Flight, " Sflight.htm , . ... In addition, L depends on the "angle of attack" between the wing and the air flow, and of course on the size and design of the wing. ...