Integration of Unmanned Aircraft Systems (Separation Monitoring)

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 can separate aircraft using this method it is not always used. 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 still 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. 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. 

References

Huerta, M. (2015, May 1). NextGen Implementation Plan 2015. Retrieved September 6, 2015, from https://www.faa.gov/nextgen/media/NextGen_Implementation_Plan-2015.pdf

McCarley, J., & Wickens, C. (2005, April 1). Human Factors Implications of UAVs in the National Airspace. Retrieved September 6, 2015, from http://www.tc.faa.gov/logistics/grants/pdf/2004/04-G-032.pdf