Frost on the wing affects aerodynamics by which of the following?

• A. Increases lift and lowers stall speed
• B. No effect
• C. Increases stall speed and reduces lift
• D. Improves stall margin

Answer: (C)

Frost on a wing changes the way air flows by roughing the surface and altering the wing’s effective shape. A smooth wing lets air follow the surface and stay attached longer, allowing higher lift before separation occurs. When frost forms, the surface becomes irregular and the wing’s camber can be effectively reduced, so the boundary layer becomes more prone to early separation. This lowers the maximum lift the wing can produce and increases drag. With less lift available at a given speed, you must fly faster to maintain level flight, which means the stall speed goes up. The frost also shrinks the margin before stall, making stalls more likely at higher speeds than with a clean wing. So the net effect is higher stall speed and reduced lift.