The FAA has awarded contracts to Rockwell Collins, Honeywell and Avidyne for development of technology that will integrate digital voice and data into air-to-ground communications as part of the next-generation air/ground communications (Nexcom) program.
Under terms of the agreements signed in February, the FAA will partially fund the development of VHF datalink mode 3 (VDL-3) radios, which are intended to replace current-generation radios with Nexcom avionics in time for the program’s initial implementation in 2009. Rockwell Collins and Honeywell are to design analog/digital VDL-3 avionics for the commercial airline market and Avidyne a line of radios for general aviation.
As announced by the FAA, Rockwell Collins Systems of Melbourne, Fla., and Honeywell Aerospace Electronic Systems of Redmond, Wash., will incorporate VDL-3 technology into existing VHF digital radio multimode equipment for airliners. Some 6,000 air-transport category airplanes will require the new avionics, a market Honeywell estimates will be worth $300 million.
Collins and Honeywell both said they plan to design and produce VDL-3 radios for general and business aviation in time for Nexcom’s full deployment, expected sometime after 2010. In all, the VDL-3 rule is estimated eventually to affect more than 170,000 U.S.-registered aircraft, a figure that will include light airplanes, helicopters, turboprops, business jets and airliners.
VHF spectrum depletion is straining the already overloaded National Airspace System (NAS). Saying that the Nexcom agreements with Collins, Honeywell and Avidyne represent a “major step forward” in the evolution of the NAS, an FAA spokesman explained that the VDL-3 avionics are needed to support the Nexcom system demonstration program, an evaluation of VDL-3 that is scheduled to be completed by the end of 2004.
According to Jim Williams, the FAA’s communications integrated product team leader, the traditional frequency-splitting method used to increase communications channels will not meet future ATC requirements for voice and data communications. In the FAA’s view, the only technology that will provide additional voice and data communications channels–and meet the stringent ICAO requirements for high reliability and low latency–is VDL-3.
In discussions on the topic, Williams and his colleagues have pointed out that the worldwide demand for air transportation is projected to grow by about 3 percent per year in the next several years. The NAS operates at or near capacity at most major hub airports and, as the traveling public is well aware, when adverse weather reduces the capacity of these airports nightmarish delays can and do occur. Such delays also put a strain on en route operations systemwide.
The solution to the airport congestion conundrum is to build more runways and ramp space. The solution to en route congestion is to create additional ATC sectors to increase the available capacity of the system. Both of these solutions require additional radio channels that allow more controllers to communicate with aircraft. Unfortunately, the VHF channels that are reserved for ATC use have been squeezed to the point of near exhaustion. Without additional channels, new sectors cannot be created and new runways cannot be used to full capacity.
Current projections by the FAA and the Mitre Corp. show that the NAS spectrum will become saturated sometime between 2009 and 2011. Certain areas of the NAS have already reached their limit, said Williams. But through proactive spectrum management efforts, it is expected that the remaining available spectrum will support the projected expansion of the NAS until Nexcom is available, he said. Planners within the FAA believe that Nexcom will ease the stranglehold that radio frequency congestion is putting on the ATC system.
Here’s how it works: using VDL-3 technology, each frequency is split into four channels to accommodate as many as four voice conversations simultaneously. Alternatively, one or two of the channels can be dedicated to data transmittal. The result is a quadrupling of the available frequencies, which the FAA believes is sufficient to serve aviation’s needs for many years to come. The new line of radios from Honeywell will be based on the company’s Quantum Series RTA-44D radio, which now provides analog voice communication and can handle low-speed (2.4 kbps) data transmissions. Scheduled for certification in mid-2004, the radio will be among the first to support controller-pilot datalink communications (CPDLC), a concept in which controllers send digital text messages to the cockpits of aircraft flying in the en route environment. The FAA believes that eventually most routine communication between controllers and pilots will be transmitted this way.
The VHF com band in the U.S. is currently segmented into 720 separate frequencies spaced 25 kHz apart. But again, in the 2009 to 2011 timeframe the FAA predicts that all 720 channels will have been assigned and that each will slowly become more congested, putting an ever tighter chokehold on air-to-ground communications. In the view of many experts who have studied the problem exhaustively, Nexcom is by far the best solution.
European aviation authorities have already further divided the 25-kHz VHF channels into three channels, each spaced 8.33 kHz apart. Technically speaking, it is impractical to attempt further channel spacing any closer because of interference issues. In fact, there have already been a number of overlap problems in Europe since the 8.33-kHz rule went into effect.
Initially, the FAA looked at the 8.33-kHz concept, but because of adjacent channel-interference issues the agency saw it as only a short-term fix. Nexcom, on the other hand, truly does segment the frequencies with zero separation penalties. The only feasible solution in the eyes of the FAA was to move from voice to digital communications, initially for routine controller/pilot exchanges such as altimeter settings, frequencies and other common messages, and eventually for most ATC exchanges.
Nexcom is being designed as a “backward compatible” system, meaning that it will support current analog voice communication alongside the new digital voice and ATN subnetwork for VDL-3 datalink communication. The system will be implemented first in the en route domain and then in terminal, tower and FSS environments.
AOPA is gearing up for a possible fight with the FAA over the agency’s plans to go digital. Although most GA pilots won’t be expected to reequip until sometime beyond 2010, AOPA is urging the FAA to maximize existing frequency use and allocations before requiring aircraft owners to purchase new radios that the association argues would provide few, if any, new benefits.