Definition
The set of pilot techniques and procedures used to stay clear of the disturbed air -- particularly the pair of counter-rotating wingtip vortices -- left behind by other aircraft, especially larger ones. Avoidance is achieved primarily through proper flightpath planning relative to the generating aircraft: taking off before the rotation point of a preceding heavier aircraft, landing beyond its touchdown point, and remaining above and upwind of its flightpath when operating in trail or crossing behind it.
Plain English
Bigger aircraft leave behind powerful spinning air currents from their wingtips that can roll a smaller aircraft uncontrollably. Wake turbulence avoidance is how a pilot positions and times their flight to stay out of that air.
Context Anchor
Pilots use wake turbulence avoidance when taking off, landing, following another aircraft, crossing behind another aircraft, or operating near large airplanes and helicopters.
Derivation
Wake' comes from the Old Norse 'vaka,' meaning the track left in water behind a moving ship. Aircraft leave a similar disturbed trail in the air, so the term carried over naturally.
Why Pilots Care
Failure to avoid wake turbulence can result in sudden loss of control, particularly dangerous for light aircraft behind heavy jets during critical phases of flight.
Analogy
Much like a small boat steering wide of the rolling wake behind a large ship to avoid being rocked.
Grounding Statement
A heavy airplane can leave invisible rolling air behind it, and that air may still be there after the airplane has moved on.
Intuition Check
Do not assume the danger is only directly behind the airplane you can see. Wake turbulence can drift with the wind and remain in the area after the aircraft has passed.
Example Sentence 1
Following a heavy jet on final, the pilot planned to touch down beyond its touchdown point as a wake turbulence avoidance measure.
Example Sentence 2
During pattern work the instructor taught wake turbulence avoidance by having the student land further down the runway after a larger aircraft.