The minimum visibility required for a flight to land has been increased from 1,500m to 5,000m in one of Calcutta airport’s four landing points because of a building in Kaikhali jutting out 11m more than the permissible limit, officials said.
The violation was detected in October 2020, but the restriction was imposed recently after one of the old navigational systems that helped pilots detect an airport from afar was replaced at Calcutta airport.
The minimum visibility requirement has been increased for the southern end of the secondary runway.
“The minimum visibility requirements for flights to land had to be increased because of a high-rise residential complex structure that has been built 11.16m more than the permissible height,” a senior official of Calcutta airport said.
“Notices have been served to the builder and the residents’ association of the building complex. However, the association has moved the court,” he said.
The building’s “illegal” portion has entered the airport’s funnel zone, a pathway used by aircraft to land and take off.
During the summer, aircraft approaching the airport from the southern end of the secondary runway face no problems. However, there could be problems during the monsoon when the visibility is lower,” said the official. “With 5,000m minimum visibility, landing could be a problem from this end of the secondary runway,” he pointed out.
“In April 2021, a notice was issued to the developer. The developer said the ownership of flats was handed over to the residents’ association,” said an airport official.
Till recently, flight operations took place with a minimum visibility requirement of 1,500m. The problem cropped up when the old navigational aid was replaced.
The Doppler very high frequency omni range or DVOR is a ground-based radio navigational aid that provides information to aircraft, increasing navigation accuracy, particularly in adverse weather conditions.
Airport officials said DVOR allows a pilot to detect an airport from a distance of 200 nautical miles or 370km.
The old DVOR has been replaced, which has been placed 50m from the earlier one at the northern end of the runway.
“The air traffic management of Calcutta airport detected problems in signalling system sent by the new DVOR. The source of the problem is the 11.16m portion of the Kaikhali building,” said an official.
The developer said he had obtained clearances for the height from the airport authorities before starting construction. “We had taken necessary clearance from the airport authorities more than 10 years back. The completion certificate was also taken from the Bidhannagar Municipal Corporation,” said Anil Kumar Loharuka, the developer.
“We had handed over the flats to the residents several years back, and their association has submitted a writ petition at Calcutta High Court against the airport’s notice.”
The airport has two runways and four landing and take-off points. The Category III instrument landing system, which allows flights to land at a minimum visibility of 50m is installed at the southern end of the main runway. The main runway’s northern end is now mostly closed as the instrument landing system is being upgraded from Category II to III.
“The work is expected to be complete by May,” said an airport official.
