A Review of "Sense and Avoid" by Lee Ewing
In his article, Lee Ewing addresses the current state of airborne sense and avoid technologies for Unmanned Aerial Systems (UAS). While the Federal Aviation Administration’s (FAA’s) progress in incorporating UAS into the National Airspace System (NAS) has been steady, it has been too slow for the liking of many critics. This article discusses the various payloads that different UAS manufacturers and operators are testing and employing to enable these systems to sense and avoid other aircraft and obstacles, in order to increase the pace of NAS integration. Examples of technologies that are being tested for large UAS include Airborne Collision Avoidance System-Xu (ACAS-Xu), which is a smaller version of ACAS modified for UAS, electro-optical sensors, and Actively Electronically Scanned Array (AESA) radar. Developments for smaller UAS include stereoscopic vision systems, miniaturized Automatic Dependent Surveillance-Broadcast (microADS-B), and ultrasound. As technology improves, it is anticipated that small UAS will incorporate a monocular vision based system, as it would be smaller and lighter than a stereo vision system. While microADS-B and ACAS-Xu would be tremendously beneficial to NAS integration, one of the biggest concerns for safety is that posed by aircraft and hazards that do not have this technology. UAS will still have the need to sense and avoid threats that may not be seen by these systems or even ground radar, similar to how pilots of manned aircraft use see and avoid. While vision based systems can meet this need, they are extremely limited in poor weather. One system that shows promise in making up for this limitation is the Passive Acoustic Non-Cooperative Collision-Alert System (PANCAS), which uses four lightweight acoustic sensors to provide spherical coverage, and has been demonstrated on UAS weighing as little as four pounds. According to Ewing, the most likely solution will depend on the size, capabilities, and requirements of the UAS itself, and will most likely incorporate various combinations of these technologies, along with augmentation from ground based sense and avoid systems such as radar.
Reference:
Ewing, L. (2017, March). Sense and Avoid. Retrieved March 25, 2017, from
http://www.mazdigital.com/webreader/48221?page=40