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Future of Air Traffic System Depends on Satellites

By | June 16, 2003

      The Federal Aviation Administration – along with other aviation agencies around the world – is moving ahead with implementation of the Future Air Navigation System (FANS), which uses satellite communication and navigation and other advanced technology to improve air traffic control over oceans.

      Speaking to the Inmarsat Aeronautical Conference held June 2-4 in Washington, D.C., Roger Kiely of the Oceanic Procedures Branch at the FAA said that FANS is at the mid-point of its implementation over the North Atlantic ocean (NAT). The goal of FANS is to improve data communications and navigational information between pilots and controllers while aircraft are over the ocean and remote terrestrial airspace to improve safety, increase efficiency and route flexibility, and ultimately reduce minimum separation between aircraft.

      According to the FAA’s Strategic Plan for Oceanic Airspace Enhancements and Separation Reductions, the FANS is a “combination of advanced ground-based automation system, enhanced on-board flight management systems, ‘glass cockpit’ map displays, satellite communications and navigation, advanced surveillance systems, and collision avoidance systems [that] will transform the current oceanic ATC system into the modern oceanic air traffic management system envisioned by the FAA.”

      Implementation of the FANS began in the mid-1990s and has accelerated in recent years. In terms of controller-to-pilot data link communications (CPDLC) portion of the FANS, New York Oceanic has implemented a fully capable CPDLC system and Gander Oceanic in Canada and Shanwick Oceanic in the UK have completed their first two phases of implementation, Kiely said. In the first phase, crews are able to make speed and altitude requests using satellite-based CPDLC rather than having to talk over high-frequency (HF) radio. The response from the air traffic controller (ATC) is an acknowledgement that the request has been received and that a response will be provided via voice.

      In the second phase, the assignment of domestic contact frequencies is carried out via CPDLC rather than HF voice communication. Analysis of HF voice traffic indicates that such messages represent a significant proportion of existing voice traffic and using CPDLC to carry out this function is a useful contribution to reducing HF voice congestion, Kiely noted.

      In the third phase, yet to be implemented, the ATC will be able to respond to aircraft altitude and speed change requests via CPDLC and to receive report leaving/level message from the aircraft. Currently, ATCs must respond via HF voice.

      Kiely noted that there are over 900 flights per day over the North Atlantic. Between 32 percent and 37 percent of those flights are using CPDLC and Automatic Dependence Surveillance (ADS).

      One of the companies offering satellite communications for the evolving air traffic control systems is Societe Internationale de Telecommunications Aeronautiques (SITA). Kathleen Kearns, SITA manager of AIRCOM Cockpit Services for North America, told the conference that satellite communications is “more reliable” than HF voice for aircraft over oceanic and remote areas.

      Kearns estimated that over 1,200 long-haul aircraft equipped with Aircraft Communications Addressing and Reporting System (ACARS) avionics use SITA AIRCOM data link services via Inmarsat satellites. Those aircraft that are also equipped with either the Boeing [NYSE: BA] FANS-1 package or the Airbus FANS-A package may also communicate with air traffic controllers via the Inmarsat aeronautical service.

      She noted that over 20 ATC agencies had contracted with SITA to use its AIRCOM data link service with aircraft having FANS avionics. Those agencies include the FAA, Eurocontrol, Korea Airports Authority, and Airports Authority of India.

      At the same time, she noted, the evolution of new data links is limited by the investment required of aircraft operators, avionics vendors and service providers. As a result, “installed systems will stay in place for many years even if some aircraft are equipped to use the new links.”

      Kearns estimated that for aircraft over the ocean or remote airspace, the response time from ACARS over Inmarsat packet mode is 10 times faster than HF voice. While speed is not an issue, improvements could be made to the Inmarsat system in terms of reliability, particularly during handoffs between aircraft and ground stations.

      She noted that ATC agencies have not yet defined any applications that call for broadband data links for aircraft, but aircraft operators are being offered services that would allow them to receive information such as graphical weather via high capacity data links. One way to reduce the costs of aircraft broadband would be to have a low capacity antenna to send out data requests from the aircraft and a high capacity antenna to receive the associated data-rich uplinks into the cockpit, she said.

      Kearns said that ATC agencies are looking into the use of ADS-Broadcast to send GPS-derived position to aircraft and ground stations. This would minimize the need for aircraft to send position data via satellite links. –Fred Donovan

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