The Invisible Wake: Why Small Planes Keep Their Distance From Big Jets

Lift does not come free. As a wing pushes air down to hold an aircraft up, higher-pressure air beneath the wing spills around the tips toward the lower-pressure air above, and the forward motion of the aircraft stretches that spill into two horizontal tornadoes trailing behind — wingtip vortices, the core of what pilots call wake turbulence. They are invisible, they can persist for minutes, and behind a large jet they are violent enough to roll a smaller aircraft beyond the limit of its controls. The strength of the wake scales with the weight of the aircraft generating it, and it is worst when that aircraft is "heavy, clean, and slow" — high weight, flaps and gear retracted, low speed — exactly the configuration of a large jet on takeoff or final approach. The vortices sink below the flight path of the generating aircraft and drift with the wind, which is why a light aircraft can encounter them well after the jet has passed. Aviation manages the hazard with separation. Air traffic control applies wake-turbulence separation minima behind larger aircraft, spacing followers by distance or time based on weight categories. Pilots are taught defensive techniques: when following a heavier aircraft, stay at or above its flight path and land beyond its touchdown point; on departure, rotate before its rotation point and climb above its path. The FAA codifies the categories and procedures in the Aeronautical Information Manual. Wake turbulence is a reminder that the sky behind every aircraft is not empty — it is disturbed, sometimes dangerously, by the very physics that held the airplane aloft. The pilot in command remains responsible for accepting or declining a clearance that would put the aircraft into another's wake, per 14 CFR §91.3.