The Federal Aviation Administration presents in the basic text Aerodynamics for Naval Aviators among Aviation Handbooks and Manuals, the following explanation of the generation of lift of a wing:
- An important phenomenon associated with the production of lift by an airfoil is the “circulation” imparted to the airstream.
- The generation of lift by an airfoil is dependent upon the airfoil being able to create circulation in the airstream and develop the lifting, pressure distribution on the surface. In all cases, the generated lift will be the net force caused by the distribution of pressure over the upper and lower surfaces of the airfoil.
- If the airfoil is given a positive angle of attack, changes occur in the streamline pattern and pressure distribution similar to changes caused by the addition of circulation to a cylinder. The positive angle of attack causes increased velocity on the upper surface with an increase in upper surface suction while the decreased velocity on the lower surface causes a decrease in lower surface suction.