Lift, Angle of Attack & 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°. What happens to Cₗ and to the lift, and why?
• 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?