Collision Avoidance for Unmanned Aircraft: Proving the Safety Case

Applications for Unmanned Aircraft Systems (UAS) abound from military and homeland security to commercial services. The ability to integrate unmanned and manned aircraft into the same civil airspace is a critical capability that will enable growth in the industry, expansion of applications, and greater utility for UAS operators.

Collision avoidance is emerging as a key enabler to UAS civil airspace access as well an important capability for the integration of manned and unmanned missions in military theaters of operation. UAS collision avoidance capabilities must be interoperable and compatible with existing collision avoidance and separation assurance capabilities including the Traffic Alert and Collision Avoidance System (TCAS) and the requirement for a pilot to see and avoid other aircraft consistent with the right of way rules.

The operational and technical challenges of UAS collision avoidance are further complicated by the wide variety of unmanned aircraft, their associated missions, and their ground control capabilities. Numerous technology solutions for collision avoidance are being explored in the community, including research sponsored by the National Aeronautics and Space Administration, the United States Air Force, The Defense Advanced Research Project Agency, and others. The Federal Aviation Administration (FAA) has requested that RTCA, Inc. develop Minimum Aviation System Performance Standards (MASPS) for UAS collision avoidance, referred to as UAS Sense and Avoid.

While the technology research activities are important to the development of these standards, analysis will be required to ensure that the technical solutions provide a satisfactory level of safety. The intent of this paper is to present one perspective on the system safety studies necessary for the community to reach consensus on the appropriate standards—a necessary step so that a collision avoidance capability for unmanned aircraft can be certified by the FAA.

The MITRE Corporation and Lincoln Laboratory have collaborated on this paper because we believe that it is important to articulate the system safety studies needed. Our two organizations bring a wealth of knowledge and experience associated with the development and implementation of TCAS. We were directly involved and/or closely associated with a significant portion of the system safety analysis that supported RTCA, FAA, Eurocontrol, and International Civil Aviation Organization (ICAO) decisions related to TCAS2 standards and certification.