The distinctive shape of the Predator unmanned aerial vehicle (UAV) manufactured by General Atomics Aeronautical Systems Inc. has become synonymous with what the public recognizes as a “drone,” mostly in the context of military operations.&nbsp;However, when the day comes that UAVs are routinely crisscrossing the skies performing tasks ranging from inspecting pipelines to surveying land to providing data and communications during and after natural disasters, NASA’s civilian research variant of the MQ-9 Predator B—the Ikhana—will have played a pivotal role in transitioning UAS from military to civil use through public and private collaboration.&nbsp;Since 2006 when NASA acquired the Ikhana—a Choctaw word which means intelligent, conscious or aware—from General Atomics to support its earth science missions, the UAV has been used to develop and demonstrate advanced aeronautical technologies and as a test bed to develop capabilities and technologies that improve unmanned aerial systems (UAS).“You could say that NASA helped develop UAS and that UAS are helping us with our various science projects and research,” says Peter Merlin, NASA senior strategic communications specialist, noting the agency’s 60-year history of UAS research. &nbsp;The Ikhana has a flight endurance of more than 20 hours and can reach altitudes above 40,000 feet. The aircraft is 36 feet long with a wingspan of 66 feet. Weighing 10,500 pounds, it can carry a 3,000-pound payload. NASA operates the Ikhana with technical support from the U.S. Air Force Medium Altitude UAS Division and the Nevada Air National Guard.&nbsp;Aside from their similar shapes, the Ikhana’s bright white color and easily recognizable red, white and blue NASA logo are hints that the types of missions it flies are much different from the dull gray U.S. Air Force Predators with their low-visibility markings.Main Mission&nbsp; One of the Ikhana’s recent missions, which will continue through this summer, has produced milestones in the development of sense-and-avoid (SAA) technology that will one day enable UAS to safely operate in the same airspace as manned civil and commercial aircraft.&nbsp;“One of our goals is to take those baby steps toward integrating unmanned aircraft systems into the national airspace.” says Heather Maliska, deputy project manager for SAA technology at NASA’s Armstrong Flight Center at Edwards Air Force Base in California. Armstrong is the host center for NASA’s Unmanned Aircraft Systems Integration in the National Airspace System project.Late last year, NASA, the Federal Aviation Administration, General Atomics and Honeywell Aerospace collaborated in conducting flight tests at Armstrong that successfully demonstrated a proof-of-concept SAA system. Further flight tests scheduled for this summer will advance development of the FAA's Airborne Collision Avoidance System for Unmanned Aircraft (ACAS Xu).“We got through this flight test and we’re hoping that it will encourage the FAA to continue to invest in this technology, that we think is a key enabler to commercial operations of unmanned aircraft,” says Brandon Suarez, General Atomics project engineer. “For all the negative talk about what the FAA has done or hasn’t done, this is really an opportunity they have to contribute significantly to the commercialization of this technology. We really think it’s important that the FAA continue to invest in ACAS Xu and that they continue to work with the community on standardization of sense and avoid.”During a five-week period at Armstrong Flight Center, nine flights were conducted which involved 170 encounters and generated more than 50 hours of flight data for the FAA to analyze. Part of the testing involved Armstrong’s Ikhana UAV and a General Atomics-owned Predator B, which marked the first air-to-air collision avoidance encounters between two UAS.&nbsp;“One of the reasons we wanted to get two unmanned aircraft in the flight test was to show that this system could work with itself,” Suarez says. “That’s really the key. We think it will provide a level of safety even greater than manned aircraft experience today.”Suarez says General Atomics has a relationship with NASA because of the Ikhana and began working with the FAA more than two years ago to integrate ACAS Xu onto the Predator B platform. The company brought in partner Honeywell Aerospace, which is developing a sensor fusion algorithm for sense and avoid. Maliska says having the companies involved is an important part of conducting research and development.&nbsp;“There’s a combination of what General Atomics brings to what we know of the Ikhana and with the Predator B, they’re the experts,” Maliska explains. “To have them be involved—at least from the platform side of things—it’s been very helpful. It’s not the sort of thing you’d do without some collaboration.”The Ikhana was equipped with the SAA system while the Predator and two manned fixed-wing aircraft served as “intruders.” General Atomics also performed the first flight tests of a pre-production air-to-air radar for SAA—the Due Regard Radar—the first radar of its kind designed for a UAV.“Our role was to be the system integrator, bringing together the technology that the FAA was developing and integrating it into the Predator B system—both the aircraft and the ground station—and then provide those bilateral relationships so that the whole project could move forward as a collaboration,” Suarez says.&nbsp;The flight tests evaluated the performance of ACAS Xu collision avoidance algorithms against air traffic with both the currently used Traffic Collision Avoidance System (TCAS II) and the proof-of-concept ADS-B, a device the FAA will require all aircraft operating in U.S. airspace to have by January 2020.“With the collision avoidance system the FAA has developed, it automatically commanded the aircraft to go to a particular heading to avoid the conflict,” says Maliska. “While there was a pilot on the ground who was there for a safety check, it allowed the aircraft to make the automatic maneuver. If there was something that we on the ground didn’t expect, the pilot was there to turn the system off and take control of the aircraft to make sure that we were making a safe maneuver.”Using what Maliska calls a “build-up approach to flight safety,” the tests began with the SAA-equipped Ikhana maneuvering with manned aircraft to trigger a resolution advisory that provides different geometries for the encounters—how the Ikhana flies in relation to where the intruder is flying. The Ikhana flew against one intruder at a time with the two aircraft flying at different attitudes.“We can make sure that our system is telling us what we think it’s going to tell us,” Maliska says. “It’s proving out our predictions.”&nbsp;The next step was the unmanned versus unmanned flights where the Ikhana flew against the Predator B aircraft. With its sensing capability, the Ikhana responded either manually or autonomously, conducting a maneuver to avoid the intruder aircraft.&nbsp;“One of the big achievements was doing the flight test on an operational unmanned aircraft because it forced us to solve all of the challenges related to integration and getting the system to work in the unmanned architecture,” Suarez notes. “It forced us to solve all of the safety of flight issues related to flying two aircraft on a collision course. None of those problems are really present when you integrate the technology on to a manned aircraft.”A significant result of the tests was that there were no surprises.&nbsp;&nbsp; “There weren’t any cases when we weren’t seeing the other aircraft and had to abort,” says Mauricio Rivas, NASA’s Ikhana project manager. “It was all planned. Any time we did get into an encounter, you knew what you were getting, and it was a smooth maneuver to avoid it.”At the ground control station, the aircraft tracks were fed into a threat resolution module where the collision avoidance maneuver algorithm worked to create self-separation between the aircraft.&nbsp;“The algorithm computes a resolution advisory—a collision avoidance maneuver,” Suarez explains. “It can be a command to climb or descend if the maneuver is against a cooperative aircraft—a transponder- or ADSB-equipped aircraft. Against a non-cooperative intruder, the maneuver is horizontal—turn right or turn left.”The collision avoidance commands are sent to the ground control station where they can be manually executed by the pilot or automatically executed onboard the aircraft by sending a command directly to the flight computer. &nbsp;As Suarez describes the process, the pilot on the ground sees the resolution advisory. The aircraft waits a few seconds, and if it doesn’t receive a command from the pilot, it will begin to perform the collision avoidance maneuver on its own.&nbsp;“The pilot has the ability to override that maneuver by taking back control of the aircraft,” Suarez says. “That’s how the majority of the flight tests ended up where the ACAS Xu portion was in automatic mode and the Ikhana was flying back and forth executing collision avoidance maneuvers.”When the intruder is no longer a collision threat, the ASAS Xu system issues a clear of conflict notice. Usually, the pilot will determine when and how the UAV should return to its previous course or mission.&nbsp;However, as Suarez notes, “It’s not always obvious after a collision avoidance maneuver what the next step should be. One of the benefits of having a pilot in command is that they can observe what happens, talk to air traffic control and negotiate a return to the clearance or continue on the current flight path.”The goal is to make UAS operations as transparent as possible to air traffic control by having the unmanned aircraft act like any other manned aircraft.Flight Test Takeaways&nbsp; Another unique aspect of the flight testing is the three displays used—two from NASA and one from General Atomics.&nbsp; “Those three displays communicated over a NASA simulation environment, which is an important thing for testing because now we can actually inject virtual traffic into the test,” Suarez says. “Hopefully in the flight tests coming up, we’ll be able to have both live traffic being tracked by the sensors on board the aircraft and virtual traffic injected from the simulation environment to provide a more realistic environment for the pilot to fly in.”The data gathered from the flight tests for the FAA will also be used by the Radio Technical Commission for Aeronautics RTCA Special Committee 228 to develop minimum operational performance standards for UAS, a key aspect of integrating UAS into the national airspace.&nbsp;“That standard is what’s going to drive the timeline for implementation and integration into the national airspace,” Suarez says. “It’s the standard that the FAA is going to use as a certification basis, which will take a couple more years to develop.”“We have had other missions where we’ve developed or tested capabilities for the Air Force,” Rivas says. “We gave the FAA a tutorial on UASs. They were part of the crew flying the airplane so they could see the nuances involved with this type of aircraft. That helps them see any issues, plus the benefits of this type of vehicle versus a manned aircraft.”Although there’s a great deal of technology to be tested and proven before UAS become a common sight in the skies, NASA’s work remains focused on that objective.&nbsp;“I think it’s fair to say that the ultimate goal will be to see these remotely piloted and autonomous systems operating in the airspace the same as any other civil and commercial traffic,” Merlin says. “We’re taking the steps to develop technologies that will help the FAA make the decisions on when they’re comfortable with integrating those airplanes into the traffic pattern. This is the beginning, and I’m sure there’s going to be a lot of work ahead.”When the history of UAS development is written, the Ikhana might very well be an iconic part of the story.Author: Patrick C. Miller&nbsp; Staff Writer, UAS Magazine&nbsp; 701-738-4923&nbsp; pmiller@bbiinternational.com

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The Ikhana, NASA’s unmanned aerial vehicle—a UAV long linked to the image of a drone—serves science while paving the way for UAS integration

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