Wake turbulence: separation standards
Intersection departure behind a Heavy: 3 minutes required (unless waived by pilot on a Large/Small following another Large).
Behind a Super (A380): 3 minutes full length, 4 minutes at an intersection.
Radar separation on final: 4 to 6 NM behind a Heavy, 6 to 8 NM behind a Super.
Mandatory phraseology: Always include “Caution wake turbulence” and name the preceding aircraft type.
Wake turbulence is generated the instant an aircraft rotates on departure and persists until the nosewheel touches down on landing. Because counter-rotating wingtip vortices sink at 300 to 500 feet per minute and drift with the crosswind, air traffic controllers apply mandatory time and distance buffers to keep following traffic safe.
The picture behind the vortex
Same-runway departure intervals
Under FAA JO 7110.65 § 3-9-6, time intervals begin the moment the leading aircraft starts its takeoff roll. You cannot issue a takeoff clearance to the trailing aircraft until the required timer expires:
| Preceding Aircraft | Trailing Aircraft | Full-Length Departure | Intersection Departure |
|---|---|---|---|
| Super (A380) | Any category | 3 minutes | 4 minutes |
| Heavy (B777, B787, A350) | Large or Small (A320, B737, CRJ) | 2 minutes | 3 minutes |
| B757 (Dedicated rule) | Small (CRJ, ERJ, GA) | 2 minutes | 3 minutes |
| Large (B737, A320) | Small (Cessna, King Air) | Runway separation (cleared once airborne) | 3 minutes (can be waived by pilot) |
The intersection departure trap
Why does an intersection departure add an entire extra minute of delay? Because an aircraft departing from an intersection (such as taxiway B2 at KSAN or taxiway EE at KJFK) starts rolling downfield from where the preceding heavy began its climb. The trailing aircraft will rotate directly inside the sinking vortex field of the previous departure.
To safely line up traffic while waiting for the timer:
Once the 3-minute clock runs down:
Radar separation on final approach
On terminal approach radar, wake separation is enforced by distance behind the leader at the runway threshold:
- Behind a Super: 6 NM for Heavy, 7 NM for Large, 8 NM for Small.
- Behind a Heavy: 4 NM for Heavy, 5 NM for Large, 6 NM for Small.
- Behind a B757: 4 NM for Large, 5 NM for Small.
Landing behind a departure
When an arrival is cleared to land on the same runway following a heavy departure, ensure the landing aircraft touches down before the rotation point of the departing heavy, or wait until the departure has cleared the departure end of the runway.
Related guides: Tower phraseology basics · LAHSO and intersecting runways · Working Tower at KSAN · VATSIM S1/S2 practice drills
Practise wake separation in the browser
ProjectATC calculates wake turbulence intervals and RECAT category matrices in real time. Releasing a regional jet inside the 2-minute heavy departure buffer will trigger an immediate score debrief penalty. San Diego (KSAN) and all five positions are free.
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