KOLKATA: One of the key radars at Kolkata airport blanked out for 10 minutes on Thursday, forcing air traffic controllers to guide at least 15 flights manually. Though not many flight operations were affected as the snag had happened at 11.35am, when most of the early morning flights had departed, controllers guided planes on the blind.
The secondary radar covers a radius of 200 nautical miles and gives the speed and altitude of aircraft. Of late, traffic controllers have been complaining about the radar's reliability. Installed in 1998, the radar should have been junked in 10 years. But it is still in service despite malfunctions being reported since 2008 when flights began disappearing randomly from the screen.
"We lodged several complaints but no action has been taken. We hope a mishap does not occur due to the technical failure," another controller said, breathing easy after the radar returned to service.
When the radar is functional, the minimum horizontal separation between two aircrafts is 5 nautical mile (9.26 km) within 60 nautical mile (111.12 km) of radar coverage. Beyond that, it is 10 nautical mile (18.52 km). But when controllers switched to manual mode, the separation had to be increased to 80 nautical mile (148.16 km) between aircrafts to avoid collision in the air.
Even then, controllers are worried as the minimum distance during manual surveillance is dependant on the flight position data provided by pilots. An error by one pilot in reporting his position or by the ATC officials in hearing it or issuing wrong direction can result in a close call.
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