AviationTire Principles Of Flight - Aeroplane Subsonic Aerodynamics The three-dimensional airflow about an aeroplane Q 3 / 5

The wake vortices behind a large aircraft begin on takeoff ... and end on landing...

at V2; in the flare.
on rotation; as the nosewheel goes down.
at V1; when lift dump is selected.
at 80kt; on touchdown.