In the engineer's lift formula L = Cl * (1/2)p * v^2 * s, what does Cl represent?

• A. Lift
• B. Wing Surface Area
• C. Coefficient of Lift
• D. Air Density

Answer: (C)

Cl is the coefficient of lift, a dimensionless factor that describes how effective the wing is at producing lift for a given dynamic pressure and wing area. In the lift formula, lift equals Cl times dynamic pressure (which is 1/2 times air density times velocity squared) times the wing area. The coefficient of lift encapsulates the influence of angle of attack, airfoil shape, camber, Reynolds number, and Mach effects on lift. For a fixed airspeed and density, increasing the angle of attack (up to the stall) raises Cl and thus increases lift; lowering it reduces lift. It’s not the lift itself, nor the wing area, nor the air density—the other terms in the equation represent those factors.