General Atomics tests UAV that can "sense and avoid" other aircraft


December 18, 2013

A Sense and Avoid (SAA) system that allows UAVs to operate safely around other aircraft in flight has been flight tested on a Predator B

A Sense and Avoid (SAA) system that allows UAVs to operate safely around other aircraft in flight has been flight tested on a Predator B

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General Atomics Aeronautical System, Inc. (GA-ASI), the maker of the Predator and Reaper Unmanned Aerial Vehicles (UAVs) has successfully completed the first of several flight tests of a prototype Sense and Avoid (SAA) system that allows a UAV to operate safely around other aircraft in flight. This marked the first time the entire system – consisting of a radar, transponder, and traffic alert system – worked together as a “system of systems” to detect the various types of aircraft it might encounter in the air.

The FAA and international agencies have long insisted that UAVs have their own “sense and avoid” systems onboard that can detect other nearby aircraft and instruct either the onboard autopilot or the ground-based remote operator of the UAV how to avoid a collision. The lack of this ability is a major reason why UAVs are not permitted to fly over much of the United States, and are restricted to special airspace that has been set aside just for that use. The addition of an SAA system to a UAV paves the way for them to operate in airspace with manned air traffic.

“We are working closely with the FAA, NASA, the U.S. Department of Homeland Security [DHS], and our industry alliances to advance the safe and efficient integration of unmanned aircraft systems into domestic and international airspace,” said Frank W. Pace, president, Aircraft Systems Group, GA-ASI. “Our Sense and Avoid capability is a key part of that goal, and we continue to make ongoing progress towards this end.”

The technology demonstrated during General Atomics' flight test does not rely on optical detection, and would be able to operate in any weather. It combines three integrated systems – the BAE Systems’ AD/DPX-7 Identification Friend-or-Foe (IFF) transponder with Automatic Dependent Surveillance – Broadcast (ADS-B) receiver; the GA-ASI-developed Due Regard Radar (DRR); and Honeywell’s TPA-100 Traffic Collision Avoidance System or TCAS.

During the test, the system had 40 pre-planned encounters with other air traffic, including some not being tracked by Air Traffic Control. The test was conducted from the Gray Butte Flight Operations Facility near Palmdale, California, a facility on the edge of the Mojave Desert and located just south of Edwards Air Force Base. The test aircraft was a Predator B model.

The three onboard systems were able to track two participating “intruder” aircraft that acted as targets for the exercise. The onboard software fused the data into a single set of tracking information that was relayed to the Conflict Prediction and Display Systems (CPDS) in front of the Predator’s ground-based pilot.

Modern aircraft have a variety of means to “see” each other in the air. It is still legal in certain areas of the US to fly with no radio at all – and even no electrical system in the aircraft. Sailplanes and gliders have no onboard power except for batteries, and ultralights can fly in uninhabited areas. The UAV SAA system would use its radar to see these targets.

General Aviation aircraft, such as Cessnas and Pipers, carry transponders, which are special radios that automatically respond when “interrogated,” or sent a special signal. Air Traffic Control normally uses transponders to tell aircraft apart on radar as each aircraft has its own code that it responds to. The TCAS – Traffic Collision Avoidance System – uses these transponders to detect the other aircraft.

The newest method is ADS-B, where each aircraft sends out its own GPS position once a second to all the other aircraft in the area. The FAA has mandated that most aircraft will have ADS-B transmitters by 2020, which will make it possible to track aircraft from space.

Since aircraft flying today may have no transponder, a current-style radar transponder, or a new, modern ADS-B radio (or some combination thereof), the General Atomics See and Avoid system uses all three techniques to detect other aircraft. The company reported that all possible combinations of radios, aircraft, and sensors were tried in the flight test.

This test is a follow-on to other individual tests conducted previously. In October of last year, the company flew the ADS-B component on a Guardian UAV, the version of the Predator being flown by the US Border Patrol, while the DRR radar flew on the Predator B in February 2013. Follow up tests are planned to continue to validate the operation of the combined system.

Source: General Atomics

About the Author
Francis X Govers III Francis Govers is the designer of over 20 land, sea, air and space vehicles and teaches robotics and the design of self-driving cars. He spent 10 years at NASA, helped design the International Space Station, participated in the DARPA Grand Challenge, and managed the only Zeppelin operating in the US. As a commercial pilot, writer, artist, musician, engineer, race car nut and designer, Francis has a serious addiction to building things that frequently gets him into trouble. All articles by Francis X Govers III

I see no reason why unmanned aircraft need to be flying over non-hostile places. I fly a general aviation airplane and the best way to prevent collisions with aircraft is called "see and avoid". Human eyes looking out the windows. All gen av planes have anti-collision lights or strobes and are usually painted in colors that make them easier to see. The predator is painted camouflage gray and has no anti-collision beacons. I'm sure flying a predator from the ground is WAY more expensive than having say a Cessna 182 with one pilot aboard. You can have all the expensive electronics aboard and I,m sure the predator will miss detecting a certain percentage of aircraft.


If the government is willing to spend money on "see and avoid" for drones, may they should spend it on equipping private aircraft with the same capabilities. After all, a craft with a live human in it is worth more than an autonomous drone isn't it?

James Pratt

James, I'm fully with you -- these civil drones (carrying human payload) should then be named Symbiots instead of Predators.

Because symbiosis is the major live sustaining principle since eons, whereas predation is recessing -- although widespread underwater, yet marginal on the ground and extremely rare in the air (between flying animals).

The reason why predation took over in human society is due to primitive opportunism as currently favored by our very young intelligence (as compared to our body) still stuck in its infantile illness state...

Reptiles evolved into birds 200 million years ago, whereas mankind got actively airborne since little more than a century -- hence, human aviation is still in its limbs... and if you believe F-18s and A-380s are the crown of aviation, well, you're probably wrong, as they're dinosaurs and therefore heading for disaster like their gigantic predecessors... (note that most recent discoveries in palaentology assert that the dinos started to decline about 10 million (!) years before the fatal meteorite impact).

Symbiosis is very much about interaction between sedentary (plants) and mobile (animal), i.e. especially flying, species, and will finally rule out predation... but we'll have to be patient!

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