Lift

Lift is the key aerodynamic force. In straight-and-level, unaccelerated flight, when weight and lift are equal, an airplane is in a state of equilibrium. If the other aerodynamic factors remain constant, the airplane neither gains nor loses altitude.

When an airplane is stationary on the ramp, it is also in equilibrium, but the aerodynamic forces are not a factor.  In calm wind conditions, the atmosphere exerts equal pressure on the upper and lower surfaces of the wing. Movement of air about the airplane, particularly the wing, is necessary before the aerodynamic force of lift becomes effective. Knowledge of some of the basic principles of motion will help you to understand the force of lift.

This page was last modified June 11, 2000
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