Posted by John Keller

ANNAPOLIS, Md., 12 Feb. 2012. Commercial aircraft operators may start using an air traffic management (ATM) communications technology called the FANS 1/A over HFDL (FOH), after officials of the U.S. Federal Aviation Administration (FAA) approved FOH as a viable means of Air Traffic Service (ATS) communications. This means commercial aircraft may start using the global High Frequency Data Link (HFDL) network to communicate with air traffic control (ATC).

This will enable pilots and air traffic controllers to exchange text and other data messages at long ranges using high-frequency (HF) radio signals, rather than VHF radio or satellite communications. FOH is an inexpensive ATC communications global alternative to satellite-based global communications, and will be most useful in controlled over-ocean airspace such as the North Atlantic and Pacific flight routes, ARINC officials say. Until now commercial aircraft could exchange only voice messages with ground controllers, not data, using HF radio signals.

HF radio signals, commonly known as shortwave radio, operate on frequencies between 2 and 30 MHz, and can achieve extremely long ranges by bouncing their signals off an atmospheric layer called the ionosphere. HF radio communications historically have been notorious for unpredictable reliability and interference, which modern digital signal processing (DSP) technology has helped to mitigate.

FANS is short for the Future Air Navigation System avionics, which enables aircraft pilots and air traffic controllers to exchange data, such as clearances, pilot requests, and position reporting. The HFDL, administered by ARINC Inc. in Annapolis, Md., enables pilots to exchange data such as Aeronautical Operational Control (AOC) messages, Controller Pilot Data Link Communication (CPDLC) messages, and Automatic Dependent Surveillance (ADS) messages with ground-based HFDL ground stations.

The HFDL is part of the Aircraft Communications Addressing and Reporting System (ACARS), a digital data link for transmitting short, relatively simple messages between aircraft and ground stations by radio or satellite.

"The FAA accepts FOH as a viable means of Air Traffic Service (ATS) communications," and agrees that FOH "will provide an effective means of Air Traffic Control (ATC) communications and position reporting," stated Margaret Gilligan, the FAA Associate Administrator for Aviation Safety, in a letter last month.

"By adopting FOH for Air Traffic Control, both pilots and controllers will be able to reduce their workloads on and off the aircraft-all the while increasing safety by automating activities previously done with voice," says Ron Hawkins, ARINC vice president of commercial aviation solutions.

The HFDL is available through ARINC that enables ground stations located around the world to provide overlapping, redundant HFDL coverage everywhere on the planet, including the north and south polar regions, ARINC officials say. For more information contact ARINC online at www.arinc.com, or the FAA at www.faa.gov.