Private Pilot License (PPL) Aerodynamics Practice Exam

What is the effect of ground effect on lift and drag during landing?

1. Increases lift, increases drag

2. Decreases lift, decreases drag

3. Increases lift, decreases drag

4. No effect on lift or drag

The correct answer is: Increases lift, decreases drag

The phenomenon of ground effect plays a significant role during the landing phase of flight. When an aircraft is close to the ground, typically within a wingspan's height, the airflow around the wings is influenced by the presence of the surface below. This influence results in an increase in lift. As the wings are close to the ground, the high-pressure air beneath the wings creates a cushion, reducing the amount of turbulent airflow that would typically separate from the wings. This allows the wings to generate more lift at a given angle of attack compared to when they are at higher altitudes. Moreover, the increase in lift due to ground effect allows pilots to land at lower speeds, which can be beneficial for controlling the aircraft at touchdown. Alongside this increase in lift, drag is reduced. The reason for the reduction in drag is that the presence of the ground limits the extent of the downwash and the energy that is dissipated behind the wings, which generally would contribute to increased induced drag. Thus, during landing, because the aircraft benefits from increased lift and reduced drag due to ground effect, it allows for a smoother and more efficient landing procedure. This understanding is vital for managing the aircraft’s approach and landing speeds effectively.