Private Pilot Private Exam

When is the greatest strength of wingtip vortices generated by an aircraft?

1. When the aircraft is heavy, clean, and fast

2. When the aircraft is heavy, clean, and slow

3. When the aircraft is light, clean, and slow

4. When the aircraft is light, dirty, and fast

The correct answer is: When the aircraft is heavy, clean, and slow

The greatest strength of wingtip vortices is generated when an aircraft is heavy, clean, and slow. This phenomenon occurs due to how lift is produced and the flow of air over the wings. When an aircraft is heavy, it requires a greater amount of lift to maintain altitude, which in turn increases the angle of attack. A higher angle of attack creates stronger lift and, consequently, more pronounced wingtip vortices. The term "clean" refers to the aircraft's configuration — with no drag-inducing devices deployed (like flaps or landing gear), which allows for a smoother airflow over the wings. Finally, when the aircraft is flying slowly, it is operating at lower speeds where vortex strength is typically more concentrated and persistent compared to when the aircraft is fast. Under these conditions, the combination of weight, clean configuration, and low speed maximizes the intensity and duration of the wingtip vortices, making it crucial for pilots to maintain safe separation from other aircraft, especially during takeoff and landing phases.