NASA, FAA, industry conduct successful UAS sense-and-avoid tests

NASA and the U.S. Federal Aviation Administration have conducted successful tests of a sense-and-avoid system aimed at incorporating unmanned aerial systems (UAS) into the national airspace.

NASA, the FAA, General Atomics Aeronautical Systems and Honeywell International Inc. demonstrated the proof-of-concept sense-and-avoid (SAA) system at NASA’s Armstrong Flight Research Center in Edwards, California, last November and December. NASA said the results will aid in the development of the FAA's Airborne Collision Avoidance System for Unmanned Aircraft (ACAS Xu).

General Atomics worked with NASA to integrate the new system aboard NASA's Ikhana research aircraft, a civilian version of the company’s Predator B. The flight-testing evaluated the SAA system in a variety of collision-avoidance and self-separation encounters between two remotely piloted aircraft and various manned aircraft. It included a sensor fusion algorithm being developed by Honeywell.

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. The Ikhana was equipped with the SAA system while the Predator and two other manned fixed-wing aircraft served as “intruders.”

“The system was automatically maneuvering the aircraft,” said Heather Maliska, Armstrong deputy project manager. “With the collision avoidance system the FAA has developed, it automatically commanded the aircraft to go to a particular heading to avoid the conflict.”

To ensure safety, a pilot on the ground stood by take control of the Ikhana.

“If there was something that we on the ground didn’t expect, the pilot was there to turn the system off and take control to make sure that we were making a safe maneuver,” Maliska said. However, there were no unexpected events, she noted.

Brandon Suarez, General Atomics project engineer, explained that in a real-world situation, after the UAS executed a collision avoidance maneuver, the aircraft's pilot would contact air traffic control on how to proceed. 

"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," he explained. "That’s really our goal, to make unmanned aircraft operations as transparent as possible to air traffic control. This aircraft acts just like any other unmanned aircraft."

Over the course of five weeks, nine flights were conducted. The team flew 170 encounters and collected over 50 hours of flight data with notable accomplishments.

“The FAA was very pleased with the data that we collected,” said Maliska.

Suarez said the successful tests give the FAA an opportunity to continue development of the ACAS Xu sense-and-avoid system.

"We’re hoping the success of these flight tests will encourage the FAA to continue to invest in this technology because we think it’s a key enabler to the commercial operation of unmanned aircraft," he said. 

Other milestones included the demonstration of a UAS collision avoidance system tested without artificial horizontal and vertical offsets applied to the algorithm as the air-to-air encounters were flown in actual conflict conditions. The flights were also the first time that a coordinated automatic response was employed by a UAS to resolve collision avoidance conflicts.

“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,” said Peter Merlin, NASA senior strategic communications specialist. “We’re taking the steps to develop technology 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.”

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