Army's 'sense and avoid' radar will let drones fly in domestic airspace

The Army has completed a two-week trial of its new “sense and avoid” technology for unmanned aerial systems and says UASes could be sharing domestic airspace with piloted craft by March 2014.

The Ground Based Sense and Avoid (GBSAA) system was put through a series of training "vignettes" at Dugway Proving Ground, Utah, and successfully steered clear of other aircraft in both live and synthetic (programmed) environments, the Army said.

"We are ready to begin the certification process" with the Federal Aviation Administration for the system, said Viva Austin, product director for the Army's Unmanned Systems Airspace Integration.


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DOD and the FAA have been working together since March on establishing rules to allow drones to perform military training flights in domestic airspace. The GBSAA uses a 3-D radar system to detect other aircraft and software algorithms to identify possible collisions and recommend how to avoid them. It would meet the FAA’s standards, the Army said.

Essentially, the Army uses GBSAA to allow unmanned aircraft to meet the FAA’s “see and avoid” requirements for manned aircraft, which, as the name suggests, means that a pilot must be able to visually identify other aircraft in the same airspace and be able to avoid hitting them.

Until now, that meant having a piloted chase aircraft flying along with the UAS or having a trained observer watching within a distance of about a 1.6 miles. It also meant unmanned craft couldn’t fly at night.

The series of seven vignettes the Army staged tested the system’s algorithms against live and synthetic “intruders.” In one vignette, for instance, two Shadow UAS craft were used against each other, one acting as the intruder, the other under the control of GBSAA. In another vignette, a synthetic UAS was flown against live traffic around Salt Lake City and simulated air traffic from Boston's Logan Airport.

In every case, the GBSAA-controlled aircraft successfully avoided entanglements with other planes, the Army said.

"The hardest part of that was actually trying to get into a situation where the maneuver algorithm was really tested, getting into a red condition," Austin said. "Big sky theory kind of held true, we almost felt like we were trying to chase people down at that point because air traffic control keeps people separated so well. It was kind of hard to put yourself in a really stressing situation and test those algorithms out really well. It was very safe, and we demonstrated that the system and the test bed were really successful."

FAA has yet to approve GBSAA, but the Army expects it to. When that happens, military UASes will be able to fly in National Air Space any time of day or night, the Army said.

The Army said it plans to start with training flights for the MQ-1C Gray Eagle, an extended-range upgrade of the MQ-1 Predator, at five locations: Fort Hood, Texas (which will get the first one in March 2014); Fort Riley, Kan.; Fort Stewart, Ga.; Fort Campbell, Ky.; and Fort Bragg, N.C.

Development of sense-and-avoid systems has been critical to the prospects for using UASes domestically. The Army has been working on it for a while, and GBSAA tracked its first UAS flight in April 2011.

In fact, GBSAA appears to be ahead of schedule. At the AUVSI Unmanned Systems Program Review 2012 conference in Washington, D.C.,  in March, Army officials said they were hoping to have the system in use domestically by 2015, a year later than now planned.

And if the program proves successful, it’s likely that GBSAA or similar technology would be applied to drones operated by civilian federal agencies, as well as state and local organizations. Many law enforcement agencies are interested in using drones, as are agencies such as NASA and the National Oceanic and Atmospheric Administration.

But a few things might have to be ironed out before domestic UAS flights become widespread. Bills introduced in the House and Senate propose that law enforcement agencies obtain a warrant before using them for surveillance.

A research team from the University of Texas at Austin recently demonstrated that domestic drones, which use unencrypted Global Positioning System signals, can be hijacked via GPS spoofing.

Reader Comments

Mon, Jul 16, 2012 JGR_LV

It sounds like an interesting test of the "empty sky" hypothesis. That's something good flight instructors include with all the good advice about situational awareness. A statistician in the 1950s took the average number of aircraft in the air on any given day throughout the world, the number of cubic miles of airspace they flew in, assumed totally random flight by all and computed the number of midair collisions that should take place. He found that his number was a very good match for the actual average number of midair collisions reported. It's a sobering comment on how well humans and machines do at avoiding collisions.

Wed, Jul 11, 2012 George Tennessee

A doppler form of radar might be able to contend with craft not normally detected by aircraft surveillance but the ground based (GB) aspect means that everything needs to be line of sight (LOS). The anticipated uses suggest that LOS will not be universally available. Topographical feature risks can be reduced with portable GB equipment but the safest implementation should include unmanned craft (UC) born detection and avoidance equipment. Communication between the GB station and the UC impose latency that could lead to problems as ranges and speeds become greater. Again a UC born solution would minimize that problem.

Wed, Jul 11, 2012

So they tested against planes. What about hot air balloons, powered parachutes, gliders, ultralights, etc. Most of these do not have a transponder on board and fly at much a lower altitude than planes. Most are not picked up on radar and pilots only need to call a tower if flying in controlled airspace.

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