EASA / CAR Part-66 · Module 8 · 8.2(b) Lift, Drag & the Stall · Cat A · B1/B2

Lift, Angle of Attack & the Stall

Objective: use L = ½ρV²S·Cʟ to explain how lift varies with angle of attack, airspeed, density and area, and why exceeding the critical angle causes a stall. The wing is 3D, drag it to look around.

Wing & airflow, 3Ddrag to rotate

Lift coefficient vs angle of attack

Angle of attack α 5 °

Airspeed V 60 m/s

Air density ρ 1.225 kg/m³

Wing area S 16 m²

Angle α

0°

Lift coeff. Cₗ

Lift L

0kN

State

L = ½·ρ·V²·S·Cₗ · Cₗ rises with α until the stall

Lift depends on air density, the square of speed, wing area and the lift coefficient Cₗ. Cₗ climbs almost linearly as you raise the angle of attack — until the critical angle (about 15° here), where the airflow separates from the upper surface and the wing stalls, so Cₗ falls even though the angle is higher. The stall is set by ANGLE, not speed.

Try this: Raise α past 15° and watch the smooth flow over the top break into a turbulent wake — that is the stall.
Try this: Hold α fixed and double the airspeed. By what factor does lift change?
Try this: Drop the density to a high-altitude value. To keep the same lift, what must the wing do?