When does an aircraft provide the most wake turbulence?

• A. When it is light, dirty and fast.
• B. When it is heavy, clean and slow.
• C. When it is light and slow.
• D. When it is heavy and fast.

Answer: (B)

The main idea is that wake turbulence is tied to how much lift the generating aircraft is producing. Heavier aircraft must generate more lift to stay aloft, which creates stronger wingtip vortices. Flying more slowly forces a higher lift coefficient to maintain level flight, which also strengthens the vortices and helps them linger longer. The “clean” configuration—flaps up and gear up—represents a high-energy lift condition without the extra disturbance that high-lift devices (like extended flaps) would add to the wake. Put together, a heavy airplane moving slowly with a clean configuration produces the most intensive and persistent wake vortices, hence the warning that this is the worst-case scenario for wake turbulence behind an aircraft. If the airplane were light, fast, or configured with high-lift devices, the wake would be less intense or dissipate more quickly.