ENACT: Generating aircraft encounters using a spherical earth model

There is ongoing research at the Federal Aviation Administration (FAA) and other private industries to examine a concept for delegated separation in multiple classes of airspace to allow unmanned aircraft systems (UAS) to remain well clear of other aircraft. Detect and Avoid (DAA) capabilities are one potential technology being examined to maintain separation. To evaluate these DAA capabilities, input traffic scenarios are simulated based on either simple geometric aircraft trajectories or recorded traffic scenarios and are replayed in a simulator. However, these approaches are limited by the breadth of the traffic recordings available. This paper derives a new mathematical algorithm that uses great circle navigation equations in an Earth spherical model and an accurate aircraft performance model to generate realistic aircraft encounters in any airspace. This algorithm is implemented in a program called Encounters from Actual Trajectories (EnAcT) and uses a number of user inputs defining the encounter events, called encounter properties. Given these encounter properties, the program generates two 4-dimensional flight trajectories that satisfy these properties. This encounter generator could be used to evaluate DAA systems as well as initiate research in automation for conflict detection and resolution.