Delhi was just a mistake away from a major air disaster on Thursday night as a radar system that gives air traffic control a handle on the traffic over most of northern India crashed for close to an hour.
The radar screens went blank at about 5.45 p.m. Personnel on duty at air traffic control panicked. Two planes were on the tarmac taxing to take off and three were in descent mode, preparing to land. And there were many more flights in the air over Delhi, on their way to Lucknow, Jaipur or Varanasi.
The Delhi traffic control handles all aircraft passing over north India — from the Pakistan border to the Nepal border, from Udhampur in Jammu and Kashmir to Varanasi in Uttar Pradesh.
“With no radar available, the radio system was the only way of knowing their position,” said a senior air traffic control officer, refusing to be identified, about the situation in the tower.
The radar shows to air traffic control the exact coordinates of planes in the air, or those waiting to take off, their altitude, their speed and the distance between them — it can get bumper-to-bumper up there.
Air control switched to something called a “manual” process: traffic controllers obtain the position of each plane from its pilot on radio, put it down on a chit of paper and stick it to a scrabble kind of a board.
“We knew the exact position of the aircraft and had to segregate them further so they stay away from each other,” said the traffic control officer, admitting a small human error or an oversight could have proved disastrous.
But it proved to be Delhi ATC’s finest hour. Nothing went wrong.
All 11 departures scheduled for that one hour of radar problems were cancelled. But some of the 25 arrivals allowed, painstakingly guided down by controllers glued to their radio sets.
A flight from Guwahati had to land as a passenger suffered a heart attack.
Sources said that the computer and air navigation system was being upgraded and that led to the glitch in the software.
“The automated computer system had failed due to which flight data processing was not possible,” said an Airports Authority of India (AAI) spokesman. AAI manages all civil air traffic in India.
“However, there were no problems with navigation and communication systems. We switched to another mode of control immediately and operations continued.”