Why is frost hazardous to flight?

• A. Frost spoils the smooth flow of air over the wings, thereby decreasing lifting capability
• B. Frost reduces drag and improves stability
• C. Frost increases wing surface area
• D. Frost has no impact on lift.

Answer: (A)

Frost on the wings is hazardous because it disrupts the smooth flow of air that the wing’s shape relies on to generate lift. A clean airfoil allows air to travel in a predictable pattern, creating the low-pressure region above the wing that produces lift. When frost is present, the wing surface becomes rough and uneven, breaking up the boundary layer and forcing an earlier transition from smooth (laminar) flow to chaotic (turbulent) flow. This roughness also promotes flow separation at lower angles of attack, meaning the wing can’t sustain the same lift as a clean wing and may stall sooner. The result is a noticeable loss of lift and an increase in drag, which reduces performance and control effectiveness—especially during critical phases like takeoff and landing. Frost does not magically reduce drag and improve stability, nor does it increase the wing’s surface area, and it certainly has a negative impact on lift.