Detect and Avoid for Unmanned Aircraft in Very Low Level Airspace

Regular aviation does usually not utilize the very low level airspace below 150 m. Even so, this altitude range cannot be exclusively reserved for the operation of unmanned aircraft. Therefore, measures have to be implemented to avoid mid-air collisions, especially with manned aviation. Primarily, the mid-air collision risk is supposed to be reduced on a strategic level preflight by thorough flight route planning and making use of advanced unmanned aircraft system traffic management concepts. Besides, the residual mid-air collision risk is supposed to be reduced on a tactical level through the use of detect and avoid systems, which support remote pilots especially during flights beyond visual line of sight. However, an accepted technical solution for unmanned aircraft does not exist at the moment. On that account, the contribution of this chapter is three-fold. First, we identify suitable detect and avoid system architectures. Second, we review suitable cooperative sensor technologies. Third, we determine the minimum required sensor range in simulations. As a result, we propose a solution for operation in European airspace that is already available: FLARM cooperative sensors onboard the UA surveille the surrounding airspace and the remote pilot tracks intruders and commands avoidance maneuvers.