Private Pilot License (PPL) Aerodynamics Practice Exam

When is the phenomenon of floating due to ground effect most noticeable?

1. Before reaching cruise altitude

2. When at less than the length of the wingspan above the surface

3. During rapid descent phases

4. While executing a go-around

The correct answer is: When at less than the length of the wingspan above the surface

The phenomenon of floating due to ground effect is most noticeable when an aircraft is at an altitude less than the length of its wingspan above the surface. Ground effect occurs when the aircraft is close to the ground, creating a cushion of air that can significantly increase lift and reduce drag. This effect is most pronounced at lower altitudes because the interference between the airflow above the wings and the surface flow beneath them becomes more influential. When the aircraft is within this critical range, it often experiences a sensation of floating or being lifted, which can lead to a longer-than-expected landing or an inability to descend as quickly as anticipated. This is especially important for pilots to understand during landing phases, as misjudging altitude in ground effect can result in a float down the runway, requiring more runway distance to achieve a safe landing. Recognizing the conditions that maximize ground effect helps pilots manage their descent and landing more effectively.