[Avionics Today 07-06-2015] NASA alongside the FAA and industry partners Honeywell and General Atomics Aeronautical Systems (GA-ASI) is currently fielding a sense-and-avoid system that could enhance the ability of unmanned aircraft to fly routine operations within the National Airspace System (NAS). Throughout the summer, NASA and industry partners will field tests — the third series of tests that build on proof-of-concept tests conducted last year — designed to engage the core air traffic infrastructure and supporting software components through both a live and virtual environment to demonstrate how an autonomous aircraft interacts with Air Traffic Controllers (ATCs) and other aircraft.
NASA's Ikhana UAS to be used in the flight trials. Photo: NASA.
The system is being fielded through the Unmanned Aircraft Systems Integration in the National Airspace Systems (UAS-NAS) project, an ongoing program that kicked off in May of 2012 and is focused on conducting research that aims to assist with UAS integration into commercial airspace.
“Our focus is on trying to do research that will provide us with results that will assist the FAA with developing rules and regulations that will ultimately allow for routine access for UAS in the NAS,” explained Laurie Grindle, UAS-NAS project manager at NASA's Armstrong Flight Research Center in California where the tests are being conducted. To this end, NASA is researching sense-and-avoid alongside other barriers to UAS integration such as command and control and human factors, but admits that sense-and-avoid is a huge hurdle.
“There are federal aviation regulations that speak to the ability for the pilot to see traffic and avoid it, but if you take the pilot out of the cockpit the pilot can’t be there to see. Until there is a system out there that allows sense-and-avoid to occur, there is a barrier to UAS integration into the NAS, because the idea is that the aircraft would operate in the NAS the way piloted aircraft do today,” said Grindle. “We’re not trying to develop a whole other NAS or make the NAS adapt to the UAS, it’s intended for UAS and the rules around them to operate within the existing regulations to the extent possible.”
The research will likely have a heavy impact on future standards as researchers for the UAS-NAS program are also working closely with the Radio Technical Commission for Aeronautics (RTCA) Special Committee 228, tasked with developing Minimum Operational Performance Standards (MOPS) for UAS detect-and-avoid technology. While the findings won’t directly impact the hotly debated Notice of Proposed Rulemaking (NPRM) for Small UAS (SUAS) systems that the FAA is currently drafting, expected to be released in 2016, the tests could offer something to airspace involved in the SUAS debate.
“While the work we’re doing right now isn’t directly related to the SUAS rule, having a sense-and-avoid system on a small UAS would definitely be beneficial,” said Grindle. “Although we’re doing research for things that are more interacting with different types of aircraft such as general aviation and commercial—all the aircraft in regular airspace that people are flying in most frequently—whereas the small UAS rule is focused on a class of airspace you don’t have GA or commercial air traffic in, if you had a sense-and-avoid system it would facilitate operations within that airspace.”
For the test trials, which began on June 17 and will continue through the end of August, researchers have equipped an Ikhana test aircraft with GA-ASI’s air-to-air radar system, Automatic Dependent Surveillance-Broadcast (ADS-B), a Traffic Alert and Collision Avoidance System (TCAS) II and a sense-and-avoid processor that is hosting Honeywell’s sensor fusion software. Also onboard are algorithms that would provide recommendations on how to stay clear of the traffic an unmanned aircraft would encounter in commercial airspace.
“By combining all of these pieces of information, that would put you in a position to detect both cooperative and non-cooperative traffic,” said Grindle.
The ADS-B on board would allow the aircraft to detect other ADS-B-equipped aircraft from up to 20 miles away while TCAS II would enable similar detection and allow the two aircraft to communicate, this is identified as cooperative traffic, according to Grindle. The radar on board would allow the UAS to identify non-cooperative traffic, or aircraft that are not equipped with sophisticated avionics, such as general aviation planes.
The tests use manned aircraft, which follow scripted flight paths, to intrude on the flight path of the UAS, prompting it to issue an alert or maneuver out of the aircraft’s way. Other tests will involve an S-3B plane, which will serve as a high-speed piloted surrogate aircraft.
The UAS-NAS fielded its first set of tests on June 17, using a Beech C90 King Air aircraft as the intruder and accomplishing 14 encounters. The team plans to fly more than 200 encounters throughout the first phase of the test series. With flight tests already started, Grindle said there haven’t been too many surprises thus far, but that throughout the coming months the UAS-NAS team will continue to expand on its research.
“We’re seeing with our flight tests what we would expect. We are able to identify other traffic when we would expect to identify that other traffic and, once we have that information, we can build on it and begin to do different encounters coming from different directions, altitudes and angles and eventually understand the whole scope of when the UAS is able to identify traffic,” said Grindle.
Following phase one with the Ikhana UAS testing, the team will also begin a second phase that will include a T-34 plane equipped with proof-of-concept control and non-payload communication systems to evaluate how well the two systems work together to interact with ATC and remain clear of other aircraft.
Ultimately, Grindle and the rest of the UAS-NAS team are hoping to answer the questions raised by the introduction of UAS into manned airspace and help smooth integration and regulation going forward.
“You can have a lot of theories, but doing flight tests allows you to demonstrate these theories in practice. With these results and the different research findings that we ascertain we could ultimately write potential requirements,” explained Grindle.