Definition
The wingtip vortex that rotates in the same direction as a crosswind and therefore drifts downwind of the flight path that produced it. In a left crosswind, the right wingtip vortex becomes the downwind vortex; in a right crosswind, the left wingtip vortex does. It tends to move laterally away from the runway or track on the downwind side and may persist as a hazard to following aircraft.
Plain English
When a wing produces lift, each wingtip leaves a spinning trail of air behind it. If there is a crosswind, one of those trails gets pushed sideways with the wind. That one is called the downwind vortex.
Context Anchor
Seen in wake turbulence and drag discussions, especially when considering how crosswinds move wingtip vortices near a runway.
Derivation
‘Downwind’ means in the direction the wind is blowing toward. ‘Vortex’ comes from Latin vortex/vertex, meaning ‘a whirling mass.’ Together: the spinning trail of air that drifts in the direction the wind is pushing it.
Why Pilots Care
Determines whether wake vortices will remain on the runway or drift away, directly affecting required separation distances from preceding aircraft.
Analogy
Think of two small dust swirls behind a truck on a windy road. The swirl on the side the wind is blowing toward gets carried farther in that direction.
Grounding Statement
In a crosswind, the downwind vortex is the one being helped along by the wind.
Intuition Check
Do not read “downwind vortex” as simply “a vortex behind the airplane.” Here, “downwind” identifies the side the wind is blowing toward, not just the area behind the aircraft.
Example Sentence 1
With a steady left crosswind, the downwind vortex from the departing 737 drifted toward the parallel runway, so the tower added spacing for the next departure.
Example Sentence 2
Pilots increase spacing when the downwind vortex is predicted to linger near the touchdown zone.