Another way of understanding the deflection of air by an airfoil, is by applying Newton s Third Law of Motion. The airfoil deflects the air going over the upper surface downward as it leaves the trailing edge of the wing. When the wing is at an angle, this deflection is even greater. According to Newton s Law, for every action there is an equal, but opposite reaction. Therefore, if the airfoil deflects the air down, the resulting opposite reaction is an upward push.
Deflection is an important source of lift.
There are some planes that do not have cambered wings. Their wings are flat and are designed to fly at very high speeds. These planes get lift only by deflection. Planes flying upside down, even with cambered wings, can deflect enough air to get lift. The amount of lift a wing can produce is governed by several factors.