Freak link jam sparks aircraft fear

Glitches in the link between the air traffic control (ATC) of the city airport and an aircraft led to the collapse of communication with a series of flights, raising fears of mid-air collisions.
Quick switching of communication frequencies and safe distance between aircraft helped avert a disaster caused by a freak frequency jam. All channel frequencies — the Calcutta ATC has six — were back in operation only after the Jet Airways’s Bangkok-Calcutta flight that faced problems communicating with the airport had landed.
ATC officials blamed the crisis on snags in the communication gadget of the Jet flight, which was carrying 141 passengers, while the airline pointed a finger at the airport. Jet said had there been any problem with the aircraft, it could not have taken off smoothly for Bangkok at 11.55am. The airport authorities said a probe would be ordered to find out what had led to the temporary collapse in communication.
“The problem started around 9.45am when the pilot of the Jet flight was communicating with the ATC through the Area South frequency. Glitches in communication, that resulted in poor voice reception, led to the jamming of the links between the ATC and other flights operating in that frequency,” said an airport official.
The ATC then put the Jet pilot on Area East and then Area South frequencies, with the same result. The Jet flight had by then come within 50 nautical miles (92.6 km) of the aircraft and, following aviation norms, the pilot was put on the Approach frequency. “It was being tailed by seven other planes that were to land in the city. The jamming happened here, too, and the ATC was cut off from all seven flights. There could have been one or more collisions but for the safe distance between the flights,” said an airport official.
Finally, when the Jet aircraft was within 10 nautical miles (18.52 km) of the airport, the pilot was put on the Tower frequency. The seven other approaching aircraft were asked to hover till the Jet flight made a priority landing at 10.18am. “Once the flight touched down, the communication channels cleared and the seven flights landed safely, an official said.