Which statement best defines a stall?

• A. A rapid decrease in lift caused by the separation of airflow from the wing's surface, brought on by exceeding the critical angle of attack. A stall can occur at any pitch attitude or airspeed.
• B. A rapid increase in lift when flaps are extended.
• C. A momentary engine stall due to fuel exhaustion.
• D. A yawing motion at high speed.

Answer: (A)

Stall is an aerodynamic condition where the wing rapidly loses lift because the airflow over the wing separates when the wing reaches and passes its critical angle of attack. Lift comes from air smoothly following the wing’s surface, and as angle of attack increases, lift rises until a critical point is reached. Beyond that point, the airflow can no longer stay attached, the boundary layer separates, and lift collapses even if your pitch or airspeed isn’t extreme. The statement that describes a rapid decrease in lift caused by airflow separation due to exceeding the critical angle of attack—and notes that a stall can occur at any pitch attitude or airspeed—captures this core idea. Other choices describe different phenomena, such as a lift increase with flaps, an engine-related stall, or a yawing motion, which are not what a aerodynamic stall is.