CONFLICT PROBABILTY ESTIMATION FOR FREE FLIGHT

Russell A. Paielli and Heinz Erzberger


Abstract

The safety and efficiency of free flight will benefit from automated conflict 
prediction and resolution advisories.  Conflict prediction is based on trajectory 
prediction and is less certain the farther in advance the prediction, however.
An estimate is therefore needed of the probabilty that a conflict will occur, 
given a pair of predicted trajectories and their levels of uncertainty.  This
paper presents a method to estimate that conflict probabilty.  The trajectory 
prediction errors are modeled as normally distributed, and the two error
covariances for an aircraft pair are combined into a single, equivalent 
covariance of the relative position.  A coordinate transformation is then used
to derive an analytical solution.  Numerical examples and a Monte Carlo validation
are presented.