The commercial drone industry is one of the fastest growing segments in technology with numerous applications evolving in areas like aerial photography, infrastructure inspection, agricultural monitoring, law enforcement, media and even the promise of package delivery. However, this growth has also created operational and safety challenges for all pilots and aviation professionals.
The FAA estimates that in 2017, 1.2 million commercial and hobbyist drones were flying in the National Airspace (NAS). By 2022, the FAA expects this number to dramatically expand to between 2.4-3.2 million drones.1 While the majority of drones fly under the 400 ft. ceiling imposed by the FAA for these types of aircraft, the potential exists for conflict with manned aviation near airports or even with low flying civilian aviation such as helicopters.
This phenomenal number of drones poses serious concerns for federal, state, and local officials creating complicated issues of safety, security, and privacy. Over the last few years, we’ve seen drones increasingly being flown in dangerous proximity to manned aircraft. Several organizations are looking for a solution referred to as UAS Traffic Management (UTM) which would safely integrate drones with other Air Traffic Management systems in the NAS. Building on its legacy of work in air traffic management for crewed aircraft, NASA is researching prototype technologies such as airspace design, dynamic geo-fencing, congestion management and terrain avoidance for a UTM system that could enable safe, efficient low-altitude operations.2
To test UTM technologies, NASA is working with commercial partners to define drone airworthiness, range and flight safety. NASA has taken a lead role in UTM design, definition, and testing in order to help alleviate flight conflicts. In addition, several demonstrations have already been conducted to prove out new technologies that can be used for the detection and tracking of this lowest tier airspace. However, a potential operational solution is still years away from being implemented and it is not clear if the FAA will have the funding to realize this grand vision.
The main problem to achieving any UTM vision is the lack of sensor coverage to detect and track drones flying below 400 ft. (“Above Ground Level” (AGL). The U.S. Air Traffic Control (ATC) System utilizes a series of radar systems that are positioned at airports across the country in order to track civilian and commercial aircraft. The U.S. airspace is covered well at high altitudes by numerous radar systems, but this radar coverage is inconsistent at lower altitudes due to terrain (mountains, buildings, and trees) blockage or distance from the radar facilities. This radar network has been designed to provide tracking for aircraft that have a large Radar Cross Section (RCS) something that does not apply to most sUAS. Most airport radars will have significant trouble detecting drones unless they are extremely close, and in many instances, the drones will be flying below the main radar beam and will not be detected at all.
Many air navigation service providers are now implementing a dedicated transponder system, Automatic Dependent Surveillance – Broadcast (ADS-B) that helps supplement the radar picture for aircraft tracking. The FAA has mandated that all manned aircraft will need to include ADS-B equipment on their aircraft to operate in most sections of the NAS by Jan 1, 2020. However, an ADS-B exemption has been made for aircraft operating below 2500 ft. Even more importantly for sUAS, the ADS-B network does not provide national coverage for flight altitudes below 500 ft. Several companies are advocating for a transponder system to be used on all sUAS, but this is a currently a fragmented solution and most drone manufacturers do not want to include any transponder due to the increased cost. Until the FAA takes a firm stand on this issue, the status quo will likely continue.
Despite ongoing initiatives by the FAA and the U.S. Government to modernize Air Traffic Control and create an Unmanned Traffic Management System, there is no system to reliably detect and track small, low-flying drones in the National Airspace today.
Many sensor systems are available today that can detect drones in flight, but the system performance is very localized and will be extremely expensive to implement across the NAS. There are pros and cons to each of these sensor types, which leads to our next post: Counter-UAS (CUAS) technology and techniques.
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