How does angle of attack relate to lift coefficient near stall, and what is the typical behavior as stall approaches?

• A. Lift coefficient increases with AoA up to CLmax; near stall flow separation causes lift collapse and stall to occur.
• B. Lift coefficient decreases with AoA until stall.
• C. Lift is independent of AoA near stall.
• D. Lift continues to increase linearly beyond CLmax.

Answer: (A)

As angle of attack increases, the lift coefficient rises because the wing generates a greater pressure difference between the upper and lower surfaces. This continues until the wing reaches its maximum lift capability, known as CLmax. At that critical angle, the airflow can no longer stay attached to the wing; flow separation begins, which drastically reduces the effectiveness of the wing and causes a rapid loss of lift, i.e., stall. Once stalled, further increases in angle of attack do not produce more lift; the lift coefficient actually falls while drag climbs.

So near stall you see lift climbing up to a peak and then collapsing as separation sets in. The other ideas—lift decreasing with angle before stall, lift being independent of angle near stall, or lift continuing linearly beyond CLmax—don’t match how real airfoils behave when flow becomes separated and the lift curve turns over.