Careless digging snaps cable, puts radars on blink

SIGNAL TROUBLE

V Ayyappan | TNN
May 13, 2009

Chennai: It was a careless move made by the driver of an earthmover that disrupted radars and delayed several aircraft for close to 12 hours from 5.15pm on Monday. The radars were restored only around 5am on Tuesday.
The cables got damaged when an earthmover in the apron area snapped an underground optical fibre cable at two places. Blips went off air traffic controllers’ screens and they were forced to switch to manual control procedures. The Airports Authority of India (AAI) is carrying out several airside development works, including readying the apron and construction of link taxiways, to ensure smooth handling of aircraft.
The optical fibre cables carry signals from radar equipment to the air traffic control (ATC) building. As the cables were severed, signals from the radars failed to reach ATC and caused a blackout. More than 200 flights suffered delays because the airport could only handle 16 flights per hour without radars.
“The first damage to a joint in the cable was rectified by midnight, while the second damage was repaired by early morning. It took a long time to locate the problem spots. Technicians had to brave snakes in the night to repair the fault,” an official said.
The cables could be repaired only after borrowing a cable laying and slicing machine from BSNL. “AAI does not have such equipment because “we do not lay or re-lay cable often and such incidents are never supposed to happen,” he added.
The AAI had provided a cable routing map to the contractors carrying out the works, but this was obviously not referred to.
Meanwhile, air traffic controllers had a tough time handling aircraft movements from 6pm until late into the night on Monday, including the peak period of 9-11pm when the airport handles up to 40 arrivals an hour. A majority of international flights arrive between 9.30pm and midnight.
Though radar shutdowns for maintenance are not uncommon at the airport, this is the first time in three years that both the radars went out of order without notice for such a long period.
Air traffic controllers have to make manual calculations when radars do not function. This slows down handling of aircraft and hikes the pressure during peak hours.