Private Pilot License (PPL) Aerodynamics Practice Exam

What effect does frost have on an airplane's lifting surfaces during takeoff?

1. It allows for a higher takeoff speed

2. It enhances the aircraft's lift capabilities

3. It may prevent the airplane from becoming airborne

4. It has no impact on the takeoff performance

The correct answer is: It may prevent the airplane from becoming airborne

Frost on an airplane's lifting surfaces can significantly disrupt the normal aerodynamic properties necessary for flight. It creates an uneven surface on the wings, which alters the airflow over these surfaces. When an airplane is taking off, the airfoil must generate sufficient lift to overcome the weight of the aircraft. The presence of frost reduces the effective lift generated by the wings and can increase drag, making it difficult for the aircraft to achieve the required speed for takeoff. Moreover, the rough texture created by frost can cause the airflow to separate from the wing at a lower angle of attack than normal, further reducing lift. This combination of reduced lift and increased drag can indeed result in a scenario where the airplane may not be able to become airborne at all, even at higher speeds. Consequently, it is crucial for pilots to ensure that lifting surfaces are clear of frost or ice before takeoff to ensure safe and efficient flight operations.