Wing Tip Vortices

What are wing tip vortices?  A picture is worth a thousand words.

A military cargo carrier and its wingtip vortices
Credit: Russell E. Cooley IV, USAF

What wingtip vortices are and how they form is relatively simple to understand.

• The air on top of the wings of an aircraft in flight is at a lower pressure than the surrounding air.  This is one of the basics of aerodynamics - Bernoulli's Principle
• The air underneath the wings of an aircraft in flight has a higher pressure than the air above the wings
• This differential air pressure causes the air below to want to take up the area where the reduced air pressure is located above the wings
• The wing tips are really the only place along the wings where this can occur.  So, the air below circles around the tip of the wing to meet the air above
• This circling action creates horizontal 'tornadoes' that trail behind the aircraft as the aircraft moves forward
• The air being pushed to the side of the aircraft's fuselage also contributes to the movement of the vortices.  They tend to move away from the aircraft and then they follow the wind direction

The generation of Wingtip Vortices and their movement
Picture used courtesy of the FAA (FAA Handbook of Aeronautical Knowledge)

Why are Wing Tip Vortices dangerous?

Slow, Heavy, airborne aircraft are the greatest contributors to the development of wingtip vortices.  These little 'horizontal tornadoes' can take a small general aviation aircraft like a Cessna or warrior and flip it completely over.  This is the absolute worse condition to be in during landing since you are low to the ground and recovery may be impossible. 

Wingtip Vortices can occur at any altitude, but again, near the ground is the most dangerous because of your proximity to it.

How can I avoid Wing Tip Vortices?

The FAA spells out a pretty simple method to avoid wingtip vortices.

Where do Wingtip Vortices begin and end?
Picture used courtesy of the FAA (FAA Handbook of Aeronautical Knowledge)

Here are some general rules

• Land beyond the touch-down point of the aircraft in front of you
• Make sure you lift off before the liftoff point of the aircraft in front of you in addition to turning away from that aircraft's flight path.  Since the larger plan is faster than you and probably climbs much faster as well, you may want to turn away so as to not 'run into' their vortex.