An Analysis of the Risk from UAS Missions in the National Airspace

As Unmanned Aerial Systems (UAS) are integrated into the national airspace, we must be careful to ensure that the hazard rate to human bystanders is sufficiently small. The first source of risk to bystanders involves midair collisions between UAS and other aircraft. The second source of risk concerns risks due to ground impact, both the bystander hazard rate due to aircraft impacting the ground as well as the dependence of crash rate on location. Here, we present first-order models adapted from the literature which estimate the risk due to these various scenarios. Model verification is then achieved through extensive analysis of historic civil aviation accidents. From this, we gain two major insights. First of all, we show that UAS already achieve manned levels of safety with respect to midair collisions. This is because general aviation aircraft routinely operate in conditions where see-and-avoid is used but is not effective. Secondly, we find that the risk due to ground collision of UAS is sufficiently small to allow operations over the majority of the United States. The models presented here are powerful tools that can be used by a general audience to objectively assess the risks associated with various missions in the national airspace.