Predicting Near-ground Vortex Lifetimes Using Weibull Density Functions

To mitigate safety hazards posed by near-ground vortex lateral transport, under instrument flight rules (IFR), parallel runway operations must adopt aircraft spacing standards that often reduce capacity. Once the phenomenon of lateral transport is understood, it is conceivable that, under IFR, new separation standards could restore some runway capacity. In this context, it is of interest to establish the probability that a wake vortex is still surviving in lateral transport t seconds after it began migrating. This paper applies survival data analysis methods to demonstrate how to generate predictions of survival probability that are specific to aircraft type. Modeling assumptions lead to a family of Weibull probability densities, a form that is useful for modeling wind phenomena.