Lift Coefficient

The lift coefficient ( or ) is a dimensionless coefficient that relates the lift generated by a lifting body, the dynamic pressure of the fluid flow around the body, and a reference area associated with the body. A lifting body is a foil or a complete foil-bearing body such as a fixed-wing aircraft.

Lift coefficient is also used to refer to the dynamic lift characteristics of a two-dimensional foil section, whereby the reference area is taken as the foil chord.

Lift coefficient may be described as the ratio of lift pressure to dynamic pressure where lift pressure is the ratio of lift to reference area.

Lift coefficient may be used to relate the total lift generated by a foil-equipped craft to the total area of the foil. In this application the lift coefficient is called the aircraft or planform lift coefficient

Watercraft and automobiles equipped with fixed foils can also be assigned a lift coefficient.

The lift coefficient is equal to:

where

• is the lift force,
• is fluid density,
• is true airspeed,
• is dynamic pressure, and
• is planform area.

The lift coefficient is a dimensionless number.

The aircraft lift coefficient can be approximated using the Lifting-line theory or measured in a wind tunnel test of a complete aircraft configuration.