page_title: Wake turbulence
section_title: Wake vortex separation
hierarchical_section_title: Wake turbulence / Hazard avoidance / Wake vortex separation
caption_attribution_description: English: Wake vortices from A-320 landing at Oakland Airport interacting with the sea as they reach ground level.
context_page_description: Wake turbulence is a disturbance in the atmosphere that forms behind an aircraft as it passes through the air. It includes various components, the most important of which are wingtip vortices and jetwash. Jetwash refers simply to the rapidly moving gases expelled from a jet engine; it is extremely turbulent, but of short duration. Wingtip vortices, on the other hand, are much more stable and can remain in the air for up to three minutes after the passage of an aircraft. It is therefore not true turbulence in the aerodynamic sense, as true turbulence would be chaotic. Instead, it refers to the similarity to atmospheric turbulence as experienced by an aircraft flying through this region of disturbed air.
  Wingtip vortices occur when a wing is generating lift. Air from below the wing is drawn around the wingtip into the region above the wing by the lower pressure above the wing, causing a vortex to trail from each wingtip. The strength of wingtip vortices is determined primarily by the weight and airspeed of the aircraft. Wingtip vortices make up the primary and most dangerous component of wake turbulence.
context_section_description: There is a number of separation criteria for take-off, landing and en-route phases of flight based upon Wake turbulence categories. Air Traffic Controllers will sequence aircraft making instrument approaches with regard to these minima. Aircraft making a visual approach are advised of the relevant recommended spacing and are expected to maintain their own separation.
  Notably, the Boeing 757, which by its MTOW falls into Large category, is considered Heavy for purposes of separation because of a number of incidents where smaller aircraft lost control (with some crashing) while following too closely behind a 757.
  Common minima are:
  Take-off
  An aircraft of a lower wake vortex category must not be allowed to take off less than two minutes behind an aircraft of a higher wake vortex category. If the following aircraft does not start its take off roll from the same point as the preceding aircraft, this is increased to three minutes. To put this more generally, an aircraft is usually safer if it is airborne before the rotation point of the airplane that took off before it. However, care must be taken to stay upwind (or otherwise away) from any vortices that were generated by the previous aircraft.
  Landing
caption: Wake vortices from a landing Airbus at Oakland International Airport interact with the sea as they descend to ground level.
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