Aircraft wake-vortex encounter analysis for upper levels

The frequency of aircraft encountering the wake of other aircraft is analyzed for given aircraft, movement, and meteorological data. The method considers the descent and decay of wake vortices for a given stratification and turbulence-kinetic-energy dissipation rate, and the advection with ambient horizontal and vertical wind. An encounter is characterized in this study by the distance between the position of a follower aircraft and the centerline of a wake vortex behind the vortex generator, and by the wake-induced lift forces or roll moments on the encountering aircraft. A linear model is used for an efficient identification of potential wake-vortex encounters for all flight segments in dense traffic regions. The method is applied to radar-observed traffic over North America in 46 days in 2010/2011, and validated against pilot-reported wake encounters and automated in situ turbulence reports. Most upper-level encounters are found for medium-size aircraft on nearly parallel flight routes during descent. En route encounters of wakes from heavy aircraft flying 1000 ft higher occur relatively rarely. The frequency of wake-vortex encounters increases with the square of air-traffic density.