Definition
The gradual weakening and dissipation of the wingtip vortices trailing behind an aircraft over time, as the swirling air loses energy through atmospheric mixing, viscosity, and interaction with surface winds.
Plain English
It's how the dangerous swirling air left behind a passing aircraft slowly fades away and becomes safe to fly through.
Context Anchor
Seen in wake turbulence discussions, especially when deciding how much spacing or waiting time to allow behind another aircraft.
Derivation
Wake comes from Old Norse 'vaka,' meaning the track left by a ship moving through water — the same idea applies to the disturbed air an aircraft leaves behind. Decay comes from Latin 'decadere,' to fall away or weaken. Together, the term simply means the trailing disturbance is fading over time.
Why Pilots Care
Knowing that wake decay reduces vortex strength helps pilots judge safe following distances and understand why separation requirements can sometimes be adjusted.
Analogy
Like the ripples behind a boat that gradually smooth out the farther back you look.
Grounding Statement
After a large aircraft takes off, the air behind it may remain disturbed for a short time before it weakens enough to be less dangerous.
Intuition Check
Do not assume wake decay means the wake disappears immediately. It means the wake weakens over time, and the rate depends on conditions such as wind, air movement, and the aircraft that made it.
Example Sentence 1
The controller added extra spacing on final because wake decay is slower in light, calm winds.
Example Sentence 2
In calm stable air the wake decay is slower, so pilots increase their distance behind the preceding aircraft.