Although a new VHF digital datalink communication system could quadruple channel capacity while retaining 25-kHz spacing, the FAA needs to ascertain if the technology is sound, if it can be certified for use in the National Airspace System and whether it is cost effective for users and the agency.
The FAA is developing a future integrated voice and data communications system which it calls next-generation air/ground communications (Nexcom), and has estimated that the cost could reach $4 billion by 2023.
Rep. John Mica (R-Fla.), chairman of the House aviation subcommittee, and Rep. William Lipinski (D-Ill.), the ranking Democrat, asked the General Accounting Office to determine to what extent the existing voice and data communications system used by the FAA can effectively meet its expected future needs, what the FAA has done to help ensure that the technology it wants to use for Nexcom will meet those needs and what major issues the agency needs to resolve before it can make a final decision.
In March 1998, after consulting the aviation industry, the FAA selected very-high-frequency digital link mode 3 (VDL-3) as the technology it wanted to use for its future communications needs. Although five other technologies–such as the current voice communications system coupled with a commercially available datalink communications system–offered some potential to satisfy a broad range of future needs, each was rejected during the evaluation process.
Then in September last year, an aviation industry panel conditionally approved the FAA’s preferred VDL-3 technology, which it plans to implement by using a phased approach to help ensure that this technology can continue to meet its future needs. To evaluate the technical and operational merits of VDL-3, the FAA will conduct three systems demonstrations to be completed between this month and October 2004.
The FAA said the tests will demonstrate the integration of voice and data communications and that the new equipment required with Nexcom is compatible with existing equipment. It will also show whether the system can be certified as safe for aircraft ops. Because the FAA plans to require aviation users to buy new radios and other equipment, it has begun to analyze the cost and benefits of VDL-3. Under the FAA’s current plans, the agency is assuming a 30-year useful life for the Nexcom technology it wants to use.
In its report to Mica and Lipinski, the GAO cautioned that emerging technologies might shorten the useful life of VDL-3 and thus reduce the overall benefits. “To help ensure that the FAA’s final selection for Nexcom is the most cost effective for the agency and aviation users,” the GAO said, “we are recommending that, as part of its cost-benefit analysis before committing to a technology, the FAA assess the potential effect of emerging technologies in light of its requirements.”
The GAO agreed that the anticipated growth in air traffic, coupled with the FAA’s efforts to reduce air-traffic delays and introduce new air-traffic services, will create a demand for additional channels for voice communications that the FAA’s current system cannot provide.
“The FAA is implementing a new communications system to respond to this challenge and also is seeking to enhance its existing ability to transmit data to provide more information to pilots, reduce errors in voice communications and better balance controllers’ workload,” the GAO told the congressmen. “Moreover, the FAA expects that its new system should be less susceptible to interference from such sources as power lines and radio and television stations and also improve security against unauthorized users.”
By way of background, the GAO noted that the International Civil Aviation Organization (ICAO) adopted the FAA’s proposed VDL-3 in 1995 as its model for worldwide use. At the same time, ICAO allowed western Europe, which was then experiencing severe frequency congestion, to further reduce the spacing between channels from 25 kHz to 8.33 kHz. While this tripled the number of channels available, it also required all aircraft flying in western Europe to install new radios.
ICAO intended that this would be an interim measure until 2004, when the FAA estimated that VDL-3 would be operational. But the FAA did not pursue developing VDL-3 in 1995, in part because its existing communications system still had available capacity to meet near-term communications needs, and because its need to modernize its ATC system became an urgent priority. The FAA resumed developing VDL-3 in 1998, but it is not expected to implement this technology until 2009.
While it is impossible to predict exactly when the existing voice communications system will run out of available channel assignments, said the GAO, the FAA and aviation representatives concur that without 23 improvements to the present system, it will be strained to provide enough channel assignments. Mitre Corp. projected that the shortage could become a nationwide problem by 2015 or sooner.
The GAO told the lawmakers that the FAA’s approach for selecting its Nexcom technology “appears prudent,” and that the FAA officials managing the program have worked with the aviation industry and are involved with other key FAA organizations to help ensure that the technical, operational, safety and cost-effectiveness issues are resolved in a timely manner.
“However, the FAA is in only the early stages of resolving these three issues,” the GAO pointed out, “and the program’s continued success hinges on the FAA’s maintaining close collaboration with major stakeholders.”
It added that the FAA’s follow through on the cost-benefit analysis, which considers how changing requirements and emerging technologies could affect the cost effectiveness of VDL-3, will be key to this success. “Otherwise, the aviation community might not continue to support the FAA in developing Nexcom, as it now does,” the GAO said.
The GAO recommended that Transportation Secretary Norman Mineta direct newly appointed FAA Administrator Marion Blakey to assess whether the requirements for voice and data communications have changed and the potential effect of emerging technologies on VDL-3’s useful life as part of its cost-effectiveness analysis of Nexcom. The GAO told Mica and Lipinski that the FAA indicated it “generally agreed with the facts and recommendation.”