Flap deployment decreases stall speed.

• A. Decreases stall speed
• B. Increases stall speed
• C. No effect on stall speed
• D. Decreases stall speed but increases stall angle

Answer: (A)

Flap deployment increases wing camber, boosting the maximum lift coefficient (Cl_max). Stall speed depends on how much lift the wing can produce at a given airspeed, and is proportional to sqrt(2W/(rho S Cl_max)). When flaps are extended, Cl_max increases, so the airplane can generate the necessary lift at a lower airspeed. That’s why stall speed decreases with flap use.

The idea that extending flaps would increase the stall angle isn’t generally correct—the change that matters for stall speed is the higher Cl_max, which lowers the speed at which stall occurs. So the correct takeaway is that deploying flaps decreases stall speed.