Wingtip vortices are the circular, spiraling trails of air that appear behind every lifting wing. They arise because high-pressure air beneath the wing spills around the wingtip into the low-pressure region above, setting the air into a rolling motion. This exchange of pressure is a direct consequence of lift: as long as a wing is producing lift, the vortices persist; when lift ceases, the vortices vanish. Their strength grows with the amount of lift being generated, and they become the primary source of wake turbulence, leaving strong swirling tunnels of air in an aircraft's path.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What are wingtip vortices in aviation?
Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift, and they are caused by pressure differences at the wingtips. Wingtip vortices are a byproduct of lift, and they form the primary unit of wake turbulence.
The FAA defines wingtip vortices as rapidly rotating air that spills over an airplane's wings. High pressure air from below the wing escapes around the wingtip, spilling into the low pressure area above the wing. This flow creates a swirling motion of the air, forming two counter-rotating vortices positioned a bit less than a wingspan apart.
Vortex circulation is outward, upward, and around the wing tips. The intensity of these vortices is inverse to both wingspan and speed. A larger extent weakens the swirl, while slower flight, like during takeoff and landing when the angle of attack is high, intensifies it. To curb this drag-inducing effect, modern jets often carry winglets-upward-bent tips that oppose drag and refine fuel efficiency, making the familiar V-shape at the ends of the wings.
Are wingtip vortices created only when an aircraft is developing lift?
Wingtip vortices exist any time an airplane's wing is generating lift. The vortices dissipate instantly once the wing stops producing lift. When the aircraft's wheels are on the ground, the wings don't generate lift, so no wingtip vortices form. The vortices are created only while the aircraft is developing lift.
Vortices are strongest when the aircraft is heavy, clean and slow, because slower aircraft flying at high angles of attack develop the greatest pressure difference between upper and lower surfaces. This lift-creating pressure differential magnifies the rotational strength of the left vortex that rotates clockwise and the right vortex that rotates anti-clockwise. All fixed-wing aircraft, from light trainers to large transports, form such vortices whenever their wings produce lift, even if the lift is not enough to let the aircraft fly.
How are wingtip vortices viewed from behind the aircraft?
When vortex circulation is viewed from behind the aircraft, the circular flow trails behind the aircraft like a pronged pair of sideways tornadoes. On the right wingtip the vortex rotates in an anti-clockwise direction as seen from the aircraft's tail, while its twin on the left wingtip turns the opposite way; both rotate inwards behind the wing. The tight circular flow is outward, upward, and around the wingtips, driven by the fact that higher-pressure air beneath the wing bleeds off to the low pressure above the wing.
If sufficient moisture is present, the cores of these vortices become visible, writhing behind the plane like gray vaporous snakes, or white trails tracing and spiraling from the wingtips. In drier air the swirling motion leaves no visible sign, even though the circular patterns of rotating air persist far behind the aircraft.
From behind the aircraft, wing tip vortices at first appeared as two semitransparent strips, spinning in the atmosphere and contorting in the wind. I noticed that as they drifted downward, the strips coalesced into a corkscrew-like shape. Soon the separate helices no longer seemed distinct but combined into a wide churning wave, looking like a lengthy aerial passageway extending across the atmosphere. The wave persisted far after the aircraft was gone.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
What do wingtip vortices created by large aircraft tend to cause?
Wingtip vortices created by large aircraft generate strong wake turbulence that imposes rolling moments exceeding the roll-control authority of encountering aircraft. Such moments cause severe roll and structural damage to smaller aircraft, and cause injury to occupants and damage to aircraft. In calm air the vortices tend to move outward from the aircraft, while crosswind will tend to influence their movement. Large jet aircraft can generate vortices that persist for many minutes drifting with the wind. Calm winds, high humidity, and still air allow wake turbulence to persist longer, so air traffic controllers enforce spacing rules to prevent smaller planes from being caught in wake of larger ones.
