NWRA AVOSS Wake Vortex Prediction Algorithm Version 3.1.1

The Northwest Research Associates (NWRA) Aircraft Vortex Spacing System (AVOSS) Prediction Algorithm computes trailing vortex trajectories and circulation decay in a plane perpendicular to the path of the aircraft that has generated the vortices. Underlying the algorithm are the following assumptions: initial vortex conditions assume that all trailing vorticity due to lift is rolled up into a vortex pair; away from the ground, the vortices are transported laterally at the speed of the local crosswind, and transport due to large-scale turbulence is not included; crosswind shear effects are not included, except as might arise from the previous assumption; and the circulation decay rate for each member of the vortex pair is the same.