How will frost on the wings of an airplane affect takeoff performance?

• A. Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability
• B. Frost will increase lift due to roughness
• C. Frost has no effect on takeoff performance
• D. Frost will only affect engine performance during takeoff

Answer: (A)

Frost on the wings disrupts the smooth flow of air, which reduces the wing’s lifting capability. When the wing surface isn’t clean and smooth, the airflow becomes rough and the boundary layer can transition to turbulence sooner. This degrades the pressure distribution over the airfoil, lowers the effective camber, and causes earlier airflow separation. The result is less lift at a given angle of attack, so you need a higher airspeed to generate the same lift, increasing takeoff distance and reducing takeoff performance. Frost can also add a small amount of weight, but the bigger effect is aerodynamic.

Lift does not increase with roughness; there is still an effect from the frost even if it seems minor. The question isn’t about engine performance; frost on the wings directly changes lift, making the option about only engine performance inaccurate. And clean wings provide the best, most predictable lift during takeoff, so any frost is a safety concern.