City streets pose problems for unmanned aircraft.

• Author: Magnuson, Stew

THE DREAM IS A fully autonomous rotary-wing unmanned aerial vehicle--one capable of flying through urban canyons, hovering above city streets or perching on building ledges as it gathers intelligence.

Researchers at the Georgia Tech's Center of Excellence in Rotorcraft Technology took one step toward that dream in August 2004 when they flew the GTMAX drone in two Defense Advanced Research Projects Agency demonstration missions at the Fort Benning military operations urban training site in Georgia.

The 160-pound aircraft with a 10-foot rotary diameter flew itself to pre-set coordinates and delivered medical supplies to a soldier within five seconds of its scheduled drop time. It later showed the ability to detect and avoid gunfire from a mock insurgent's gun.

While the demonstrations were a success, there "is a long way to go" before the goal of full autonomy is achieved, said the center's director, Daniel Schrage. It will take at least another five to 10 years of software development before rotary-wing UAVs can swoop among tall buildings searching for insurgents completely independent of operators, he said at an Institute for Defense and Government Advancement conference.

Smoke and dust, electrical wires and the limitations of global positioning system technology in proximity to buildings are among the obstacles, he added.

Rotorcraft UAVs that can freely operate in an urban environment are high on the Army's wish list, Paul Bogosian, aviation program executive officer, told reporters at a briefing.

"There's no question it offers attributes that any hovering platform can offer in that kind of [urban] environment," he said.

Pentagon planners see rotary-wing UAVs as part of a suite of unmanned sensors. Ideally, fixed-wing drones will cruise at higher altitudes while the helicopters maneuver in for closer looks. The ability to hover and perch gives them an advantage over higher-flying aircraft.

"If you're going to really have to hover and spend much time with staring sensors and zero-ground speed sensors, then you're going to want a hovering capability," said Schrage.

The four-year, DARPA-funded project involved about a half-dozen research universities, with each taking responsibility for developing software programs that demonstrated different capabilities. Georgia Tech integrated the package onto a Yamaha RMAX drone normally used for agricultural applications.

The effort required a mix of software programmers, and aeronautical, electrical and...