FAA Aircraft Dispatcher (ADX)Navigation and ATCHard
ATC is providing radar separation between two IFR aircraft on approach. The lead aircraft is a Boeing 747 (Heavy) and the trailing aircraft is another Boeing 747 (Heavy). What is the minimum radar separation ATC must apply between these aircraft due to wake turbulence?
- A4 nautical miles
- B5 nautical miles
- C3 nautical miles
- D6 nautical miles
Show answer & explanationAnswer & explanation
Correct answer: A. 4 nautical miles
Per FAA wake turbulence separation standards, when a Heavy aircraft is following another Heavy aircraft, ATC must apply a minimum of 4 nautical miles radar separation due to wake turbulence hazards. Separation increases when a smaller category aircraft follows a Heavy.
Why the other options are wrong
- B. 5 NM applies to Large aircraft following a Heavy, not Heavy behind Heavy.
- C. 3 NM is standard non-wake-turbulence radar separation, insufficient for Heavy-behind-Heavy.
- D. 6 NM applies to Small aircraft following a Heavy aircraft.
Wake Turbulence Radar Separation
ATC applies increased radar separation minimums behind Heavy and B757 aircraft due to wingtip vortex hazards, varying by the weight category of the trailing aircraft.
- Heavy behind Heavy: 4 NM
- Large/B757 behind Heavy: 5 NM
- Small behind Heavy: 6 NM
- Small behind B757: 6 NM; Large behind B757: 5 NM
Memory trick: 4-5-6: Heavy-Large-Small, separation grows as weight shrinks