Encounter modeling for sense and avoid development

Integrating unmanned aircraft into civil airspace requires the development and certification of systems for sensing and avoiding other aircraft. Because such systems are typically very complex and a high-level of safety must be maintained, rigorous analysis is required before they can be certified for operational use. As part of the certification process, collision avoidance systems need to be evaluated across millions of randomly generated close encounters that are representative of actual operations. New encounter models are under development that capture changes that have occurred in U.S. airspace since earlier models were developed in the 1980s and 1990s. These models capture the characteristics of small, general aviation aircraft that may not be receiving air traffic control services as well as typically larger aircraft that are squawking a discrete transponder code. Both models allow dynamic changes in airspeed, vertical rates, and turn rates in a way that was not possible previously. This paper describes the process used to construct the encounter models, how the models may be used in the development of sense-and-avoid systems for unmanned aircraft, and their application in an analysis of an electro-optical system for collision avoidance.