Definition
A pair of spinning air masses trailing from an aircraft's wingtips that rotate in opposite directions to each other. The vortex from the left wingtip rotates clockwise (viewed from behind), and the vortex from the right wingtip rotates counterclockwise. They form whenever a wing is producing lift and persist behind the aircraft as wake turbulence.
Plain English
Two spinning tubes of air left behind by an aircraft's wings, one off each wingtip, spinning in opposite directions. They are the main hazard in another aircraft's wake.
Context Anchor
Seen in wake turbulence discussions, especially when learning why a larger aircraft’s flight path can leave disturbed air behind it.
Derivation
Counter-rotating means rotating in opposite directions to each other. Vortex comes from the Latin vortex, meaning a whirling mass, like water spiralling down a drain. The pair label captures the key fact: the two trailing whirls spin opposite ways, not the same way.
Why Pilots Care
These vortices create persistent wake turbulence that can roll or upset a following aircraft, requiring proper separation distances.
Analogy
Picture two long, invisible whirlpools lying sideways behind an airplane. One twists left while the other twists right.
Grounding Statement
After a heavy aircraft takes off, its wings can leave two spinning tubes of air behind it that drift and sink near the runway path.
Intuition Check
Counter-rotating does not mean the vortices cancel each other out. It means the two vortices spin in opposite directions while both can still be hazardous.
Example Sentence 1
The instructor explained that the counter-rotating vortices from the departing 737 would drift across the runway with the light crosswind, so we held short for an extra two minutes.
Example Sentence 2
During approach the instructor pointed out how counter-rotating vortices drift with the wind and can linger near the runway.