T.F. Green Airport's Airfield Ground Radar System Acts as Eyes in Fog

Sep. 14--WARWICK -- Ever gotten the butterflies while hurtling through the night on a foggy runway at 175 miles an hour?

At T.F. Green Airport, relax. The controller in the tower sees your aircraft clear as day and knows for a fact the runway ahead is clear.

Even in zero visibility, a new airfield ground-radar system called Airport Surface Detection Equipment, or ASDE-X, sees every plane, car, truck and snowplow, and even that coyote loping along the edge of the taxiway.

Computers collect signals from radar and two kinds of surveillance sensors and assemble them into a single real-time image that controllers monitor in the tower.

The Federal Aviation Administration is installing ASDE-X in 34 midsized airports at a cost of about $100 million, starting with Green, Milwaukee and Orlando, Fla. The system is designed to prevent "incursions," two objects trying to use the same runway or taxiway at the same time.

Controllers at Green started testing ground radar a year ago and certified it fully operational in May. The FAA unveiled the system yesterday.

Before ground radar, controllers at Green had to rely on pilots and drivers to report their positions via radio. In clear weather, they could verify those reports by sighting the aircraft or vehicle from the tower. But whenever visibility was poor or nonexistent, they had no way to confirm the positions reported, and no way to spot a vehicle or aircraft that had not reported in.

Air traffic controller Ted Michalakes, watches the sky and monitor for new ground radar system that sees every plane, car, truck and snowplow. The system is designed to prevent "incursions," when two objects use the same runway at the same time.

The system not only sees aircraft but picks up signals from their transponders, identifying the specific aircraft to controllers, their speed and other data. The Airport Corporation is equipping its ground vehicles with similar transponders.

Controllers at Green handle more than 300,000 takeoffs and landings a year, almost all without incident.

According to the FAA, Green's most recent runway incursion occurred 10 months ago, on Nov. 17, 2004. Without clearance from the tower, a Cessna taxied onto Runway 34 while a Boeing 737 was on its takeoff roll. The general aviation pilot saw the commercial jet approaching from the opposite direction and turned off, onto a taxiway. The two aircraft came within 1,100 feet of each other.

(The ASDE-X system was in its second month of testing at the time but was not used to detect the incursion, according to FAA spokesman Jim Peters.)

Ground radar would have been invaluable to controllers on the night of Dec. 6, 1999, when an arriving United jet became lost on the airfield in heavy fog as the pilot attempted to taxi to the terminal. A FedEx cargo jet was cleared for takeoff on a runway partially obstructed by the United flight, and a potential collision was avoided only because the FedEx Boeing 727 lifted off before reaching the United jetliner.

Because of a series of miscommunications, the tower then cleared a USAirways jet to take off on the obstructed runway. The pilot twice refused and held in place until the United jet was located and directed to the gate.

In Washington, the National Transportation Safety Board made a computer animation of the incident and held it up as one of two close calls that showed an urgent need for ground radar at airports across the country. Even in zero visibility, controllers would have had the tools to "see" the United flight taking a wrong turn on a taxiway after landing.

Until ASDE-X was installed at Green, Milwaukee and Orlando, only the very largest airports in the country had ground radar, a much-less-sophisticated system known as ASDE-3.

Officials said yesterday ASDE-X will eventually be upgraded to sound an audible alarm to warn of a runway incursion. Currently, a controller has to view the screen to see any potential conflict developing.

After a period of logging four to six incursions a year, the tower at Green reported no incursions in 2001 and 2002, one in 2003 and two last year.

Peters attributed the decrease to "a recognition that runway safety should remain a top priority."

"We began to really look at it and devote resources to additional training of controllers and education of pilots," he said.