NASA Flies Large UAS Without Chase Plane

In June NASA flew its large unmanned Ikhana UAS for the first time in public airspace without a chase aircraft. The modified General Atomics MQ-9 took off from NASA's Armstrong Flight Research Center in Edwards, California, and flew a 2.5-hour, 415-nm mission through some of the busiest civil airspace in the U.S. at a variety of altitudes.

The flight was conducted under an FAA certificate of waiver or authorization and the aircraft was equipped with detect-and-avoid technologies including airborne radar developed by General Atomics Aeronautical Systems, a Honeywell traffic alert and collision avoidance system, a detect-and-avoid fusion tracker, ADS-B In and Out, and a conflict prediction and display system that provides the pilot situational awareness similar to what's available when a pilot is on a manned aircraft looking out the window. The system used Ku-band satcom to talk to ATC and to transmit data to the ground and the aircraft was operated with the TCAS II system's automatic capability engaged, enabling it to maneuver the aircraft if the other detect-and-avoid equipment on the aircraft failed. 

The flight took off from Edwards, entered Class-A airspace west of Edwards at 20,000 feet, then turned north toward Fresno where the flight was handed off to Oakland ARTCC. The flight then turned south toward Victorville, requiring communication to be transferred back to Los Angeles. On the return, the aircraft pilot began a descent of the aircraft over Tehachapi into Class E airspace at 10,000 feet and initiated an approach into Victorville at 5,000 feet, coordinating in real time with tower controllers at the airport. The aircraft then exited public airspace and returned to Armstrong. The flight spent an hour outside of Class E airspace without a chase aircraft and 31 minutes below 10,000 feet exercising its detect-and-avoid system in a VFR environment.

“We never had to employ our detect-and-avoid system to avoid traffic, but we did have tremendous surveillance on all the proximate aircraft,” said Sam Kim, NASA's technical lead for the UAS-NAS project. “The crucial exchange with ATC was as we approached Victorville at 9,000 feet. We actually had traffic called out to us. With our detect-and-avoid systems, we knew exactly where he was. We had him on radar only because his transponder was not functioning correctly. And we actually replied with a traffic detected call, where a UAS that is equipped with the right equipment is acknowledging that he has the traffic, analogous to calling 'traffic in sight' and assuming separation responsibilities for that aircraft.” 

Fabrice Kunzi, detect-and-avoid lead for General Dynamics Aerospace Systems, said the technology aboard Ikhana actually provided a greater level of safety than that aboard traditional manned aircraft. “In many ways, the detect-and-avoid system that is on the Ikhana [MQ-9 Predator derivative] is more capable than the collision and avoidance systems that are required on today's manned aircraft and is even more capable than a pilot's ability to see other aircraft. So it exceeds actually the average pilot's ability to see and avoid. The system and its capabilities do provide that critical item for manned and unmanned aircraft to fly together and share the NAS.”

Kunzi said the system has the capability to provide “deconfliction for tens of aircraft at a time” and coordinates deconfliction between aircraft. “The system also provides solutions for what is called a multi-intruder encounter and will optimize the instructions to the pilot based on what is the safest for that particular situation,” he said. 

Kunzi said the flight “is really an achievement for industry as a whole” because it validates the RTCA's subcommittee 228 technical standards for see and avoid, which in turn provide a standard for the regulatory basis for government approval and certification of this type of detect-and-avoid system. 

Kim noted that the Ikhana (66-foot wingspan and 4,900 pounds) is a Class 2 UAS and that the program's next goal is to miniaturize the detect-and-avoid system to the scale where it can fit aboard a Class 3 UAS, an aircraft with a 20-foot wingspan with a gross weight of 1,300 pounds. He called the June flight “a few small steps we took in the right direction” to validate UAS see-and-avoid technology.