Private Pilot License (PPL) Aerodynamics Practice Exam

What is ground effect?

1. A decrease in lift close to the ground

2. The interference of the Earth's surface with airflow patterns

3. An increase in induced drag when landing

4. A method to enhance fuel efficiency during flight

The correct answer is: The interference of the Earth's surface with airflow patterns

Ground effect refers to the phenomenon that occurs when an aircraft is flying close to the ground, typically within one wingspan's length of the surface. In this proximity, the interaction between the aircraft's wings and the ground influences the airflow patterns around the wings, which can lead to a significant increase in lift and a decrease in induced drag. This occurs because the presence of the ground alters the airflow, reducing the downwash and the pressure differential on the wings. As a result, the wings can produce lift more efficiently, allowing the aircraft to fly at lower airspeeds without stalling. Consequently, pilots often experience a change in handling characteristics during takeoff and landing due to this effect. The correct understanding of ground effect is crucial for pilots, especially during takeoff and landing phases of flight, as it can enhance performance but also requires careful management to prevent abrupt changes in lift when transitioning from ground effect to free air.