Rare event simulation for potential wake encounters

A flying aircraft produces two coherent rotating vortices of air in its trail. If another aircraft flies into one of these vortices, it can experience an un-commanded roll. Because of the potential risk, wake separation standards exist to significantly reduce the probability of such events. Thus, wake encounters are inherently rare. As new procedures and technologies are proposed to increase the capacity of the airspace, rare-event simulation is necessary to evaluate to the safety of proposed changes. This paper explores the performance of a rare-event splitting technique in the context of estimating probabilities of potential wake encounters. The goal is to identify good strategies for the splitting method while using a relatively simple model for the wakes. Suggestions for the choice of the level function and the locations of levels are given.