Definition
The minimum spacing in distance or time that ATC or a pilot must apply between aircraft to avoid encountering the disturbed air (wake vortices) trailing behind a larger or heavier aircraft. The required spacing varies based on the weight categories of the leading and following aircraft and on whether separation is being applied in flight, on approach, or for departure.
Plain English
Extra space or time kept behind a bigger aircraft so the swirling air it leaves behind has time to weaken or drift clear before the next aircraft flies through it.
Context Anchor
Used during arrivals, departures, and visual approaches, especially when a pilot is following another aircraft to the runway.
Derivation
Wake' comes from the Old Norse vök, meaning a track or trail left behind in water — the same idea as a boat's wake. Aircraft leave a similar trail in the air, but instead of ripples it's two powerful spinning vortices off the wingtips. 'Separation' simply means the spacing kept between them.
Why Pilots Care
Prevents sudden rolls or loss of control from wake vortices, especially behind heavy aircraft.
Analogy
A boat leaves a rough trail in the water behind it. An aircraft leaves an invisible rough trail in the air behind it.
Intuition Check
Do not think of separation as only a measured distance. For wake turbulence, safe separation can also mean staying above the aircraft ahead’s flight path, touching down beyond where it touched down, or waiting long enough for the wake to move away.
Example Sentence 1
The tower instructed the Cessna to extend its downwind to provide wake turbulence separation behind the departing 737.
Example Sentence 2
During the visual approach, the pilot maintained proper wake turbulence separation from the preceding aircraft.