WAM: New technology hits GA

September 24, 2009

A new surveillance system introduced in Colorado allows air traffic controllers to track aircraft in areas not covered by radar.

The new system, called Wide-Area Multilateration (WAM), requires no new equipment for aircraft and uses a network of relatively small sensors on the ground to pinpoint the location of aircraft in remote, mountainous regions. The sensors send out signals that are received and sent back by aircraft transponders.

Surveillance in nonradar areas can improve the safety and efficiency of flights in the near term while the FAA transitions to satellite-based surveillance in the NextGen air transportation system. AOPA has been involved in many NextGen planning groups and has worked to ensure that aircraft have access to airspace not covered by radar and can make the best use of existing technologies.

“AOPA advocated strongly for access to nonradar areas in the recent mid-term NextGen task force,” said AOPA Senior Director of Airspace and Modernization Heidi Williams. “By using existing equipment in aircraft, this new system can give pilots access to one of the key capabilities of NextGen starting right away. It is a great transition tool while the FAA puts the infrastructure in place for the next stages of modernization.”

The FAA plans to use WAM in the near-term as a bridge to Automatic Dependent Surveillance–Broadcast (ADS-B), the surveillance system that will be the backbone of the satellite-based NextGen air transportation system. 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, according to an FAA press release.

WAM began initial operations Sept. 12 at Yampa Valley-Hayden, Craig-Moffat, Steamboat Springs, and Garfield County Regional-Rifle airports in Colorado. These areas are popular ski resorts, but the mountainous terrain makes radar surveillance impossible and forces air traffic controllers to operate on a one-in, one-out basis during instrument conditions. WAM triangulates the signals returned by Mode C and Mode S transponders and displays aircraft locations on controllers’ screens, allowing the controllers to see all aircraft from the ground up and route traffic more efficiently and safely.

The system was deployed in Colorado under a joint cost-sharing agreement between the Colorado Department of Transportation and the FAA. The FAA will monitor how the system works at the four Colorado airports over the next year to determine further deployment; future locations planned for the system include Juneau, Alaska, and runway monitoring in Detroit, Mich.