FAA plan will reduce voice congestion in the airwaves

The Federal Aviation Administration detailed on Jan. 6 its plan to replace many routine voice transmissions between controllers and pilots with digital data messages—a move designed to increase the number of aircraft that controllers can manage by reducing congestion in the airwaves.

The Controller Pilot Data Link Communications (CPDLC) program will allow pilots and controllers to transmit data directly between computers on the ground to computers in the cockpit, rather than reading out the information.

This will help alleviate a frequency congestion problem, which limits the number of planes a controller can communicate with at any one time, thereby reducing the number of aircraft that controllers can allow to fly in a particular sector.

"Data Link will free up voice channels for more urgent traffic," said James Williams, the ADL product lead at the FAA. "And it means controllers will be more efficient because they can handle more traffic."

CPDLC also will allow the controller workload to be distributed more evenly among the controller team. Normally, the radar controller is responsible for direct communication with a pilot. However, CPDLC will allow that controller to hand off some of the work to other controllers who can send the information via a digital text message instead.

"Data link overall is not a workload reduction tool but a workload redistribution tool. It allows us to distribute the workload better to the overall controller team," said Martin Cole, the National Air Traffic Controllers Association's national representative for data link.

Today many sectors are reaching capacity in terms of the voice frequencies available for communication, Cole said. "There is a point we would reach fairly quickly where we wouldn't be able to absorb the [anticipated] traffic increases in the voice-only environment," he said. "Data link also gives controllers another means to communicate with the aircraft during the times voice communications are unavailable."

Transmitting, via text, routine, nontime-sensitive messages between the controller and pilot—such as when a plane leaves one airspace sector and enters another or when a pilot must change an altimeter setting—would reduce the load on the voice channel by about 25 percent, said Frank Buck, outcome manager for data link at Mitre Corp. "In the busy sectors, we found that 25 percent of voice usage was hello and good-bye," he said. With data link "we can offload that to other controllers."

Data link is important to the airlines as well. "Data link technology is to aviation what fiber optics were to communications," said Robert Baker, executive vice president for operations at American Airlines. "I think it is akin to a revolution in the way we will manage air traffic in the future."

American Airlines will test the prototype CPDLC system in about two years, Baker said. "This will require us to look past parochial interests and keep our eye on the prize: a more efficient air traffic control system," he said. Currently, airlines use data link technology for such applications as sending connecting gate information to flight attendants, but it is not yet used for air traffic control.

CPDLC is also an important first step in helping the FAA overhaul its aging air and ground communications systems and replacing them with digital technology. Last fall, the agency unveiled a $1 billion program called Nexcom to do just that. Eventually, CPDLC and Nexcom will be integrated, but details on how that integration will occur are still fuzzy.

The FAA first plans to use CPDLC in the en route air space between airports, with initial operational capability expected in June 2002. The agency has funded $166 million for the project through 2007 to develop the initial release of the program. Computer Sciences Corp. is developing the software, and Arinc Inc. will serve as the communications service provider.

The FAA said it eventually plans to expand the program to air space over the ocean and immediately around airport terminals, agency officials said.

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