Detect, Sense, and Avoid

     Air traffic control centers (ATCC) take responsibility for managing, takeoff and landing, and separation of manned aircraft operating within the national airspace (NAS) using ground-based radars at terminal radar control (TRACON) and air route traffic control centers (ARTCC). Along with voice communications with pilots Traffic Alert and Collision Avoidance Systems (TCAS) aboard most aircraft help maintain safe distances to avoid potential collision dangers. In the middle of all these technology sits the human factor, pilots and Air traffic controllers (ATC), using their senses and brain computing power to maintain safe operations in the air and on the ground. ATCs have an unenviable, highly stressful, job of ensuring the safe operation of over 90,000 planes flying across the U.S. everyday (over 5, 000 aircraft flying overhead at any given time), according to the National Air Traffic Controllers Association. In spite of the increasing density of air traffic pilots and ATCs manage to effectively perform their jobs to monitor aircraft and maintain separation.

      UAS operators, in essence, must play both parts to prevent collisions. As pilots of UAVs they must have situational awareness of their aircraft’s surroundings using flight cameras and instrumentation readings, all from the vantage point far removed from the aircraft itself. They must also perform as quasi ATCs in conjunction with other operators to maintain separation in segregated airspace. In non-segregated airspace, though, UAV operators must comply with local ATC instructions if they are to operate safely within the vicinity of commercial and general aviation (GA) aircraft. Communications between all involved must maintain a high degree of reliability and incorporate failsafe measures on the UAV. This is particularly important on the mid to upper size categories of UAVs where the potential for catastrophic collisions increases proportionally.

     Automatic Dependent Surveillance-Broadcast (ADS-B), currently in use and will be required on all commercial and GA aircraft by the year 2020, takes the sense and avoid capabilities of aircraft to the next level (Automatic Dependent Surveillance-Broadcast (ADS-B), 2014). Augmenting transponders, which can serve as backup, ADS-B can significantly enhance the UAVs’ ability to detect, sense and avoid other aircraft on the grid makes an argument for allowing safe integration into the NAS. Yet, this technology comes at a cost and may not be applicable to all UAV categories. The equipment necessary to utilize ADS-B adds weight and power demands on the UAV. While these requirements may be negligible on medium range to MALE/HALE UAV designs, they are of note when incorporating into smaller unmanned platforms where space, weight, and power are at a premium. The effect of the additional demands on the system comes into consideration compared to endurance or payload capacity.

      In looking towards integration of its UAS into the NAS, the US Air Force issued a request for information to technology vendors to build sense and avoid systems for its drones, called the Common-Airborne Sense and Avoid (C-ABSAA) Program (Cooney, 2014). The AF seeks alternatives to the Certificate of Authorization process and increase its mission options as military and commercial use of UASs expands. This, however, only addresses one issue of the many facing UAV integration into the NAS to include ensuring reliable command, control and communications, failsafe actions in loss-link situations, network security and anti-jamming or anti-spoofing capabilities, and interference issues in saturated RF spectrum. These are just a few issues that the UAS industry and aviation and government agencies face with the challenge of integration of UAVs into the NAS.

Reference

Automatic Dependent Surveillance-Broadcast (ADS-B). (2014, April 16). Retrieved from Federal Aviation Administration: http://www.faa.gov/nextgen/implementation/programs/adsb/

Cooney, M. (2014, April 17). Layer 8. Retrieved from Network World: http://www.networkworld.com/community/blog/air-force-wants-technology-will-let-drones-sense-and-avoid-other-aircraft