UNMANNED CRAFT ACES FLIGHT TESTS PLANE SAFE NEAR OTHERS IN AIR.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - In a first step toward allowing unmanned aircraft to share the skies with airliners and private planes, the National Aeronautics and Space Administration wrapped up a successful series of flight tests of a collision-avoidance system.

Researchers flight-tested a system to provide enough information to a pilot on the ground to let him maneuver an unmanned aircraft out of the way of other planes. The researchers flew aircraft ranging from a 1940s vintage Stinson to an F/A-18 Hornet fighter toward an unmanned Proteus aircraft.

``The detection ranges were a little less than we expected, but varied greatly from about 2.5 to 6.5 nautical miles, based on the structure and radar cross-section of the target aircraft,'' said Glenn Hamilton, UAV subsystems project manager at NASA Dryden. ``We picked up the F/A-18 farther out, due to its large radar signature, but because of its higher speed, it didn't give us a whole lot of extra time to make an avoidance decision. On one head-on scenario, we had a 610-knot (about 700 mph) closure speed - not a whole lot of time to decide.''

The unmanned Proteus used in the tests was built by famed aircraft designer Burt Rutan's Scaled Composites. The spindly, odd-looking craft was fitted with a high-frequency Amphitech radar designed to detect other aircraft within a six-mile range.

NASA officials say the April 1-4 tests, sponsored by the Dryden Flight Research Center, gave them increasing confidence that a pilot on the ground flying an unmanned aircraft can safely detect other aircraft and avoid collisions.

More work will be required to come up with a system that could be fielded, officials say.

NASA wants unmanned aircraft for scientific and aeronautics search, but the craft must be able to operate safely and routinely within the same airspace as civilian planes.

The U.S. military also is interested in technologies that will allow the growing number of unmanned aircraft - such as the Global Hawk and Predator spy planes used in Afghanistan and Iraq - to use the same airspace as manned aircraft. That would let the unmanned aircraft be used in homeland defense, not just in foreign combat zones.

NASA is in the planning stages for continued research. The effort is aimed at safely adding unmanned aircraft into the national airspace in five years, said Dryden spokesman Alan Brown.

``It will be focusing on (flight safety) certification and operational issues,'' Brown said.

About $8 million is expected to be allocated for the research in the 2004 NASA budget. NASA is expecting the Federal Aviation Administration and the Defense Department to contribute to the program.

For safety, the aircraft in the tests were forbidden to get within 500 feet of each other, and they kept at least a 200-foot difference in altitude.

As a backup, the Proteus was equipped with a system that detects aircraft with transponders - a device that sends out aircraft identification signals - at a range of up to 35 miles.

As another safety measure, there were pilots in Proteus' cockpit who could have taken control if needed.

In all 20 scenarios flown, the Proteus pilot on the ground was able to detect the presence of other aircraft that posed the potential for collisions and maneuver out of the way, NASA officials said.

Two scenarios using a hot-air balloon were scheduled to be included in the tests, but winds forced the team to drop those tests.