Holistic approach to safe operation of small UAS in class G airspace

Abstract

This paper presents a system designed for Beyond Visual Line of Sight (BVLOS) Unmanned Aircraft System (UAS) operations incorporating light (<7 kg) and frangible structures, Automatic Dependent Surveillance-Broadcast (ADS-B) transceivers and light weight radar for air traffic detection and avoidance. In recent years, there has been a steep increase in number of UAS and the trend indicates a further increase. Federal Aviation Administration (FAA) projections point towards a total commercial UAS fleet size greater than 400 000. The congestion of air traffic leads to an increase in the risk posed to general aviation and efforts are taken to mitigate this development. A holistic collision avoidance protocol requires attention to be paid to pre-flight mission planning, integration of cooperative collision avoidance equipment and techniques, development of non-cooperative collision avoidance equipment and an appropriate choice of platform. The main focus of this paper is the feasibility study of a non-cooperative traffic detection system for small UAS. The proposed method is a continuous wave radar. It is light weight (450 g), low power (5 W), operates at 24 GHz and has an Equivalent Isotropically Radiated Power (EIRP) of +20 dBm. The system was tested in ground-to-air experiments that showed a detection range of 400 m of a target with 1.1m2 Radar Cross Section (RCS) corner reflector mounted facing the radar. There was no sign of interference with the test-target aircraft due to the use of the system. Confirmation of the minimum detection range was achieved with air-to-air tests, when the radar clearly picked up the same target at a distance of 480 m (the maximum range tested). The increased situational awareness of the aircraft with the radar mounted on board showed a result better than human eye detection of the small target aircraft due to a larger RCS than visual signature of the target. Based on the proven feasibility of radar technology for collision avoidance on board small UAS, further work can be pursued into optimization of such a system, versatility of platform and product manufacturing.