Which of the following can change the critical angle of attack?

• A. Airfoil shape
• B. Weight of the aircraft
• C. Load factor
• D. Airspeed

Answer: (A)

The key idea is that the critical angle of attack is determined by the wing’s geometry and how the airflow behaves over it. The angle at which stall starts—when the boundary layer separates and lift falls off—is set by the airfoil’s shape and surface characteristics. Changing the airfoil shape (camber, thickness distribution, surface finish) alters where and how the flow detaches as the wing pitches up, so the stall angle changes accordingly. Weight, load factor, and airspeed affect when you reach stall in terms of speed or load required, but they do not set the fundamental angle at which the flow will separate for that wing geometry. Hence, only modifying the airfoil shape can change the critical angle of attack.