Despite recent events, the FAA is continuing its modernization of the National Airspace System (NAS), and controller-pilot datalink communication (CPDLC) remains a key building block in its Operational Evolution Plan.

But a planned joint test of CPDLC next year by American Airlines and the Miami Air Route Traffic Control Center has been scaled down and pushed back, delaying the program by at least 18 months and prompting suggestions that the business aviation community might be recruited in American’s stead.

Jeff Griffith, FAA’s deputy of air traffic services, told the RTCA fall forum that because of the recent downturn in the economy, the airlines may not be able to support anything other than a small test of CPDLC. “We have to move ahead with some type of system test,” and he said there might be other people in the NAS system who could help do that, such as individual corporate operators and/or a large fleet such as NetJets.

Although it was not widely publicized, the FAA has been predicting for some time that the demand for radio frequencies could exceed capacity by the end of this decade unless some action is taken to reduce frequency congestion.

Reducing Voice Frequency Congestion

He stressed that 82 percent of what a controller puts over the air by voice could be eliminated through text messaging, and voice congestion could be further reduced by
allowing flight crews to acknowledge message receipt with an automatic text reply.

Griffith said that text messages could include weather information, sigmets, airmets, notams and ATIS, and eventually air traffic control messages, route clearances and
re-routes. Tests are already being conducted on VHF Digital Link (VDL) Mode-2, an
air/ ground digital data communications network that is a precursor to VDL Mode-3 (VDL-3), which will be used for both voice and data communications.

Griffith noted that there are some other fleets around the NAS that could be pressed into service. “It could be corporate, it could be airline, it could be commuter,” he said. “So we are suggesting possibly that maybe there is another way to look at this–even involving FAA aircraft and our FAA Technical Center–where we can prove the concept and be sure that we’ve got a good system.”

At an FAA-sponsored industry day in the fall last year, the agency surprised many in attendance with the warning that the industry was running out of frequencies in the 25-KHz spectrum, saying that all 760 channels would be used up by 2004 or 2005. The shock was further compounded when the agency revealed that VDL-3, the chosen alternative, would not be in place until later in the decade.

“Frequency management is an invisible issue to some of us,” said John Kern, a retired Northwest Airlines pilot who heads the FAA’s Nexcom Aviation Rulemaking Committee (NARC). “But not to a lot of other people. So our question really was: if we are running out now, how are we going to fill the gap, how are we going to equip the airplanes, how do we rationalize the investment, how do we handle the rulemaking and a lot of other things that had to happen?”

Out of that, FAA Administrator Jane Garvey formed NARC and asked it to look at two alternatives–VDL-3 for voice and data, or using 8.33-KHz channel spacing and VDL-2 for data. But she also urged the group not to rule out other alternatives.

“The timeline for investment is important for the industry,” Kern said. “If the industry invests in [one system] later this decade, I don’t think we’re going to invest in another set 10 years later.”

Karl Grundmann of NASA, who is chairman of RTCA’s Special Committee 198 (SC-198) on next-generation communications (Nexcom), said that Nexcom in its broadest connotations includes all aspects of transitioning ATC communications from an analog voice system to a digital voice and data communications system. “It’s more than a radio,” he added.

Nexcom encompasses more than just the acquisition of a new ATC radio, Grundmann explained, and includes all of the issues associated with it, such as spectrum, policy, procedure, acquisition, certification, training, facilities and maintenance.

FAA acting director of Free Flight Phase 2 John Thornton told the RTCA gathering that the original target for initial daily use of CPDLC by American Airlines and the Miami Center was to have been this coming June. Participants in the program were Rockwell Collins, American’s avionics vendor, and Arinc, which was to provide the Aeronautical Telecommunications Network (ATN)-compliant VDL-2 network.

That plan was changed by September 11, Thornton said, in part because it was determined that there probably would not be a sufficient number of equipped aircraft to make Miami the launch site and to have the operational system working.

“So then we switched gears and started planning the operational evaluation that we would conduct,” Thornton said. “A lot of work that was already accomplished for the testing on the way and at Miami, I think, gives us a good bit of what the operational evaluation would look like. We would be able to look at certain things, get an understanding of the ground system certification, learn more about the VDL-2 and ATN, the Miami center adaptation–there is still a lot of value there for us.”