System Is Entirely Transponder-Based, Requires No New Equipment On Aircraft

A new surveillance system introduced by the FAA in Colorado allows air traffic controllers to track aircraft not covered by radar in remote, mountainous regions.

“The new system, called Wide-Area Multilateration, lets us see aircraft we couldn’t see before due to the rugged terrain,” said FAA Administrator Randy Babbitt. “It improves the safety and efficiency of those flights and saves time and money for passengers and operators.”

The FAA and the Colorado Department of Transportation are sharing the cost of Wide-Area Multilateration, which began initial operations on September 12th at Yampa Valley-Hayden, Craig-Moffat, Steamboat Springs and Garfield County Regional-Rifle Airports. The mountains in those areas are popular ski destinations but make radar coverage impossible because radar signals cannot pass through solid objects.

The resulting flight limitations are compounded by seasonal bad weather, which causes flight delays and cancellations. The Colorado Department of Transportation estimates an average of 75 aircraft are delayed each day at remote airports from November to April.

The new system is comprised of a network of relatively small sensors deployed in remote areas. The sensors send out signals that are received and sent back by aircraft transponders. No other aircraft equipment is required. System computers are able to determine the precise location of aircraft by triangulating the time and distance measurements of those signals. Controllers are able to see those aircraft on their screens as if they were radar targets.

Wide-Area Multilateration (WAM) is being used in the near term while the FAA rolls out Automatic Dependent Surveillance–Broadcast (ADS-B), the satellite-based surveillance system that will be fully deployed nationwide by 2013. WAM will then serve as a backup to ADS-B in the event of a GPS outage and provide an additional source of traffic broadcast to properly equipped aircraft.

Under the joint cost-sharing agreement, the Colorado DOT paid for the equipment, physical site preparations, power and telecommunications for the new system. The FAA will operate and maintain the system, eventually upgrading it with ADS-B.

The FAA will monitor how the system works at the four Colorado airports to determine further deployment.

FMI: www.faa.gov