Blank zone risk in airport link failure

Calcutta: A thousand aircraft entering the Calcutta air space daily face a safety hazard as they fly through “blank zones” where the pilot fails to communicate with the air traffic control at the city airport.
Sources said “inadequate network” of the airport’s Very High Frequency Omni Range communication system has turned 1,000 nautical miles — 1,852km — on various routes covering Calcutta into blank zones.
The Airports Authority of India is aware of the problem and has asked the Calcutta ATC to identify the zones. “The study is almost complete and we are expecting a report soon,” said an AAI official.
“Once we fly into a blank zone, the voice communication with the ATC is snapped abruptly. Attempts to communicate through other higher frequencies, too, don’t work,” said a senior Air India pilot. “During emergencies like sudden bad weather, we try to communicate through other aircraft which are in the coverage area,” he said.
Pilots in a blank zone also face “severe problems” in changing altitude or direction. “With the ATC out of bounds, there is no one to guide us if we need to go down or fly up. In such situations we take a call based on our interactions with adjacent aircraft,” a pilot pointed out.
The problem is most acute on the Calcutta-Port Blair route as almost the entire 500 nautical miles (926km) of the stretch fall in a blank zone. On the Calcutta-Bagdogra route, flights have no communication link with the airport on a 100-nautical mile stretch (185.2km) between Katihar and Bagdogra.
29/06/10 Sanjay Mandal/Telegraph

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Categories: Airports Jun 2010, Safety Jun 2010