NAS moving toward all-digital technology

The Federal Aviation Administration anticipating more crowded skies in the years ahead is considering how it may make a wholesale move to more efficient digital-based communications throughout the National Airspace System.

For several years the FAA has been exploring the use of data link technology in which voice and data information is transmitted in a digital format. The FAA is interested in digital technology because it requires less bandwidth than traditional analog communications and is frequently more reliable.

Last month the FAA asked vendors to submit information on their strategies for providing data link services for the next five to 10 years. The agency will consider this information as it decides whether to lease or buy Aeronautical Data Link (ADL) services and equipment when the time comes to migrate its operations.

The request for information signals a slight but important change in the FAA's activity in data link research: Agency officials now discuss ADL not in terms of "if" but "when" and "how."Although questions about data link's technology and operating procedures have yet to be answered "we know we want to go digital rather than analog " said Steven Zaidman director of systems architecture and program evaluation at the FAA.

After reviewing industry responses - as well as its own studies on the technology - the FAA plans to turn the project over to an FAA Integrated Product Team early next year to begin developing an acquisition.The size of the procurement will depend on what route the FAA decides to take. In general the agency sees three options: lease services and equipment provide its own services and buy the equipment or a mix of the two. The FAA will consider such factors as life-cycle costs and the ability to get up-to-date technology Zaidman said. "Whether we lease or buy we will go with whatever the market can support."

The FAA and the aviation industry expect ADL to have a major impact on airspace operations. In particular data link communications will head off potentially serious problems with congestion in the radio spectrum.

In part the problem stems from the Federal Communications Commission's decision to sell off portions of the spectrum that previously had been set aside for government use. Air traffic is growing about 4 percent a year creating more voice traffic particularly in the major hubs. "That leads you to [strive for] more efficient use of the spectrum and analog won't do that but digital will " Zaidman said.

In addition ADL has the potential to improve air traffic services by eliminating unnecessary voice traffic altogether.

For example as an aircraft progresses through airspace sectors nationwide the pilot must constantly coordinate shifts in communications frequencies with controllers. If coordination can be done digitally "that will make it more precise and give them time to concentrate on flying the airplane and controlling [the traffic] " said Ray Hilton director of air traffic management at the Air Transportation Association Washington D.C.

In the long term transmitting information from computer to computer will play a major role in advanced air traffic management methodologies.

The FAA sees itself moving to a system called free flight in which airlines will choose the most efficient route at a given time. Computer systems will play a major role in approving that route and ensuring that aircraft maintain safe distances. Data link will provide the means for transmitting the relevant route and positioning information directly from the cockpit of an aircraft to the air traffic management system.