DAVID LEARMOUNT / ATHENS
Confusion over interception procedures in the event of a communication breakdown threatens safety of airliners
Airliners approaching national airspace are in danger of being shot down by fighter aircraft if there is any communications breakdown as pilots are often unaware of the correct procedures to follow.
The threat has prompted airlines to brief pilots on what to do in the event of a fighter interception, says the International Air Transport Association (IATA).
Investigation by IATA of the procedures to be followed on no-communications interception found that the US Federal Aviation Administration's Aeronautical Information Manual had reversed the meaning of certain interception visual signals. Even International Civil Aviation Organisation documents were incorrect, although the on-line version has been corrected.
Recent events have shown that neither the military nor airline pilots know the exact procedures to be adopted in the event of an interception combined with a radio failure, says IATA. International agencies say they have had to alert airlines and air forces to the danger since the 11 September suicide hijackings raised the possibility that airliners might have to be shot down in extreme circumstances.
In July, says IATA, a Boeing 747 with total radio failure was "approaching western Europe" from the Atlantic, but when it was intercepted the airline pilot did not understand or react to the visual signals made by the fighter pilot. Although that airliner was not in serious danger, says IATA's director of safety Paul Woodburn, it would have been had the event occurred since 11 September.
In October, a Boeing 737 operated by UK low-fare airline Go was intercepted by a French fighter when it lost communication with air traffic control (ATC) while crossing the France/Spain border. The situation was resolved when communications were re-established. However, the 737's transponder was still giving ATC its identification and the aircraft was adhering to the flight-planned route, so the shoot-down risk was reduced.
An airliner's transponders and traffic alert and collision avoidance system (TCAS) can, however, increase the likelihood of mistaken shoot-down.
If the fighter pilot approaches the airliner without adopting the correct procedure of switching off the interceptor's altitude encoding system, it can trigger a TCAS resolution advisory warning on the airliner. This, when followed by the airline pilot, will look like intercept avoidance by the fighter.
Since 11 September, US ATC has had Department of Defense personnel on duty, with a hotline to the White House for shoot-down authorisation. The US Air Line Pilots Association is reminding members of procedures - communicate on 121.5mHz if the radio is serviceable, or if the interceptor rocks its wings and turns gently away, the airliner should follow.
Source: Flight International