FAA Airline Transport Pilot (ATM)Transport Aerodynamics and High-Altitude OperationsEasy
A flight crew is departing behind a heavy transport-category aircraft that is climbing slowly with flaps and gear retracted. Which condition produces the strongest wingtip vortices for wake turbulence purposes?
- ALight, clean, and slow
- BHeavy, dirty, and fast
- CHeavy, clean, and slow
- DLight, dirty, and fast
Show answer & explanationAnswer & explanation
Correct answer: C. Heavy, clean, and slow
Wingtip vortex strength is greatest when an aircraft is heavy (requiring high lift/high angle of attack), clean (flaps/slats retracted, concentrating lift near the wingtips), and slow (further increasing the angle of attack needed to produce required lift).
Why the other options are wrong
- A. Light aircraft generate weaker vortices due to lower required lift.
- B. A dirty (flaps extended) configuration spreads lift and reduces peak vortex strength somewhat.
- D. Light and fast conditions reduce lift coefficient and vortex strength.
Wake Turbulence Strength
Wingtip vortex intensity increases with aircraft weight, clean configuration, and slow airspeed (high angle of attack).
- Heavy + Clean + Slow (HCS) produces strongest wake vortices
- Vortices sink and can persist for several minutes
- Greatest hazard occurs during takeoff and landing phases
Memory trick: Heavy, Clean, Slow = HCS = 'Hazard Creates Storms' of vortices