Separation of Unmanned Aircraft Systems

Separation of Unmanned Aircraft Systems

Scott E. Leishman
ASCI 637 Unmanned Aero Sys Ops & Payloads

Embry Riddle Aeronautical University-Worldwide

One of the largest concerns with integration as it relates to unmanned aircraft systems (UAS) is safety. As part of the safety discussion it is important to address the separation of unmanned aircraft systems from other unmanned aircraft in addition to separation from manned aircraft.

“The ability to maintain adequate separation between aircraft is a prerequisite for the safe integration of unmanned aircraft into the National Airspace System (NAS).While safe separation from other aircraft can generally be assured through standard air traffic control (ATC) operations in operations under instrument flight rules (IFR) and instrument meteorological conditions (IMC), there will be times in which UAS may be flying under visual flight rules (VFR) (or a corresponding designation) in which the detect, see and avoid (DSA) capabilities are essential (McCarley, 2005).”  

 So this leads us to ask how can the separation of unmanned aircraft be monitored and maintained (among other unmanned aircraft and manned aircraft) in the NAS?

One way to monitor and maintain separation of aircraft is through the use of air traffic control services. The primary purpose of the ATC system is to prevent a collision between aircraft operating in the NAS and to organize and expedite the flow of traffic. Controllers such as myself use various tools to accomplish this mission. One tool that is used is through the use of radio detection and ranging or RADAR. This is a fairly straightforward approach to separation where the air traffic controller has a RADAR scope and observes a “target” this target is displayed as a blip on a scope which in turn simulates an aircraft, this is called a primary target. There is also a secondary block of information that is displayed next to the primary target which displays the aircraft’s speed, altitude, and squawk code. Controllers use this information to separate aircraft from known and/or observed conflicts.  While controllers often separate aircraft using this method it is not always used, and it is not always a requirement to have air traffic control services provided. So we must ask what other ways can we separate unmanned aircraft from manned aircraft and other unmanned aircraft? This leads to the discussion about DSA technology. The UAS have to be able to detect, sense, and avoid other UAS as well as manned aircraft. One way manned aircraft are accomplishing this is through the use of Automatic Dependent Surveillance Broadcast (ADS-B). From the NextGen Implementation plan of 2015 ADS-B is:

“The more precise, satellite-based successor to radar. ADS-B Out uses GPS to determine an aircraft’s location, airspeed and other data. It broadcasts that information to a network of ground stations (which relays the data to air traffic controllers) and to nearby aircraft equipped to receive the data via ADS-B In. ADS-B In provides operators of properly equipped aircraft with weather and traffic information delivered directly to the cockpit (Huerta, "NextGen Implementation Plan 2015").”

Future users will be required to be equipped with ADS-B out by 2020 but will be a requirement only for those aircraft operating at or above 10,000 feet. This does not resolve the conflict for aircraft operating at lower altitudes which is one of the questions that are being asked as part of the integration process.  At least 14 companies, including Google, Amazon, Verizon and Harris, have signed agreements with NASA to help devise the first air-traffic system to coordinate small, low-altitude drones, which the agency calls the Unmanned Aerial System Traffic Management (Levin, July 24,2015, para.5).

Another technology that could be used by unmanned aircraft is the terminal collision avoidance system (TCAS) but the problem with using this “manned” aircraft technology is that it is much too large for use in small unmanned aircraft. This lack of sufficient technology to cover all categories of unmanned aircraft is troubling because we are not able to take advantage of integrating all unmanned aircraft safely. Without the introduction of newer technologies, those wishing to use UAS not capable of detecting, sensing, and avoiding other aircraft, will find themselves extremely restricted under the proposed rules regarding integration.

Alternatives that appear to be solution include systems like Low altitude Tracking and Avoidance System (LATAS).  

“Current aviation technology is unable to locate and track drones due to their small size and the low altitudes at which they fly. This makes it difficult for air traffic controllers to manage an increasing number of commercial and hobbyist drones while maintaining the safest airspace in the world” (LATAS, “LATAS Brings Order”, n.d., para.2)

“Operating over the world-wide cellular networks and satellites, the LATAS (Low Altitude Traffic and Airspace Safety) platform connects leading airspace management technologies, such as sense and avoid, geo-fencing and aircraft tracking, into a service package for commercial and recreational drone operators as well as regulators and air traffic controllers (LATAS, “Say hello to LATAS”, n.d., para.1)”

This DSA need stems from those users wishing to utilize their UAS beyond line of sight, and having these technologies will help to allow those users to do so. Because there is not a defined method of separation, legislature will be required to define what technology is acceptable, and until it has done so UAS will continue to suffer the consequences and be limited to line of sight operations for those UAS that are unable to accommodate technology that would allow them to operate beyond line of sight, such as TCAS, and ADS-B. Questions that still remain to be answered will be are UAS tracked by the same equipment the FAA has ordered traditional aircraft to install by 2020, known as ADS-B? Or will the nation’s cellular network be adapted for UAS monitoring? Additionally will independent recreational fliers, who are now exempt from most drone regulations, be required to adhere to new rules? How will the system handle rogue operators who don’t cooperate? Without answering these questions and creating sufficient technology, advancing UAS into the future will have hindered progress.

VIDEO LINKS

References

Huerta, M. (2015, May 1). NextGen Implementation Plan 2015. Retrieved September 2, 2015, from https://www.faa.gov/nextgen/media/NextGen_Implementation_Plan-2015.pdf

Latas. (n.d.). Retrieved November 7, 2015, from http://flylatas.com/

Levin, A. (2015, July 24). Google Wants a Piece of Air-Traffic Control for Drones. Retrieved November 7, 2015, from http://www.bloomberg.com/news/articles/2015-07-24/google-has-way-to-unclog-drone-filled-skies-like-it-did-the-web

McCarley, J., & Wickens, C. (2005, April 1). Human Factors Implications of UAVs in the National Airspace. Retrieved November 2, 2015, from http://www.tc.faa.gov/logistics/grants/pdf/2004/04-G-032.pdf