Karen Walker/ATLANTA

THE US FEDERAL AVIATION Administration plans to award two contracts in March for competitive development of a system which "tags" returns from an airport surface-movement radar with aircraft identity. AlliedSignal and Cardion plan to bid for the airport-traffic identification system (ATIDS), one element of the FAA's overall airport surface-traffic automation (ASTA) effort.

The goal of the ASTA project is to increase airport safety and capacity by providing advances in surface-traffic control similar to those already being introduced in air-traffic control (ATC). Identifying aircraft on the approach and tracking them from touchdown to the gate, and from the gate to take-off, is an important part of the planned system.

Major US airports are already installing the Westinghouse Norden Systems ASDE-3 surface-movement radar and associated conflict-detection software. The ASDE-3 can detect aircraft, displaying them as blips on the controller's screen, but it cannot identify them.

Cardion has just completed demonstration of its co-operative area precision-tracking system (CAPTS) at Atlanta, Georgia's Hartsfield International Airport. The CAPTS works by listening to automatic transmissions from aircraft Mode S transponders. These once-a-second "squitters" are detected by remote receiver/transmitters (R/Ts) located around the airport.

Using a technique known as multi-lateration, which compares the target's location as detected by each R/T, the system can determine aircraft position, to within 7.7m, says marketing manager, ATC systems, Robert Mosier. Aircraft can be accurately located and labeled out to 9km (5nm) from the runway.

The R/Ts, modified Rockwell-Collins TCAS 2 traffic-alert and collision-avoidance systems, can also interrogate ATC transponders on aircraft not equipped with the Mode S. Mosier says that airport-surface coverage will require between five and 15 R/Ts. There are five at Atlanta, providing coverage of the north side of the airport only.

The CAPTS was installed at Hartsfield in March 1995 and has demonstrated a detection reliability of 92% and a position accuracy of better than 7.5m, Mosier says. The Atlanta system has now been reconfigured to demonstrate its use as a precision-approach and runway monitor (PARM) to allow reduced aircraft separations on parallel approaches.

The R/Ts have been repositioned to provide coverage, out to 30km along the approach path, and Mosier expects the system to offer better accuracy, than a $6 million precision-approach-monitor radar, "at less than a quarter of the cost". In addition, the PARM function will provide simultaneous coverage of parallel approaches and departures, runways and taxiways, he says.

Cardion says that the CAPTS will work with lower-cost ground-movement radars, such as the FAA's proposed ASDE-X, or as a stand-alone surface-surveillance system at airports lacking radar. The Administration plans to award an ATIDS production contract by March 1997.

Source: Flight International