If the lift coefficient increases by deploying flaps, what happens to stall speed?

• A. Stall speed decreases.
• B. Stall speed increases.
• C. Stall speed remains unchanged.
• D. Stall speed becomes zero.

Answer: (A)

Stall speed is determined by how much lift the wing can produce at a given weight, density, and wing area, and it is tied to the maximum lift coefficient the wing can achieve before stalling. The relationship is V_stall = sqrt( (2W) / (rho S Cl_max) ). When flaps are deployed, the wing’s lift capability increases because flap camber and area effectively raise Cl_max. With a higher Cl_max, the wing can generate the required lift at a lower airspeed, so the speed at which stall occurs drops. In other words, deploying flaps allows you to fly slower without stalling, even though you may experience more drag. This is why the correct outcome is that stall speed decreases.