An artistâs impression of the new air traffic control tower
April 6: A "technical" decision to reduce the proposed height of a new air traffic control tower at Calcutta airport by almost half is being reviewed after the state government wrote to the Airports Authority of India (AAI), seeking feedback on doubts raised by field crew.
The government's intervention is in response to a representation to chief minister Mamata Banerjee by the Air Traffic Controllers' Guild, which wants the height of the tower to be restored to the originally proposed 112 metres. The tender for the contract mentions a height of 57 metres.
"The airport has two runways and three of the four ends have an instrument landing system; so it won't be much of a problem to have a taller tower. The airport building is expanding too and the parking bays are moving further away. Taller the tower, better the visibility," said Kailash Pati Mandal, secretary of the ATC Guild's regional unit.
The guild had appended a technical study to its representation, explaining why a tower of the originally specified height was a better option.
An ATC tower is used to monitor and guide flights and the height of the structure enables a clear view of aircraft landing, taking off or taxiing. Several ATC personnel whom Metro spoke to said a 360-degree view of moving aircraft from a reasonable height was crucial to averting collisions in the technical area and also during take-off and landing.
Sanjay Jain, regional executive director (eastern region) of the AAI, said the "technical reasons" behind reducing the proposed height of the tower were being reconsidered. "Discussions are on at the Delhi headquarters. We are waiting for the decision. Although the tender has been floated, it is still possible to change the plan," he said.
Another AAI official said that if the tower were to 112 metres in height, it could obstruct a key navigational aid because of its proximity to the runways. The VHF Omnidirection Range navigational aid helps in knowing the position of an aircraft as well as during a "non-precision approach" for landing. The transmitter on the ground informs the ATC tower about the angle and distance of the aircraft from the airport, helping it guide the pilots in the absence of an instrument landing system.
The opposing view is that at 57 metres, the tower would not provide an unobstructed picture of the entire technical area and the parking bays that have shifted further away since the integrated terminal was built.
The AAI had first invited contract bids to build a new tower in 2008, fixing the height at 86 metres. This was taller than Mumbai airport's 83.8-metre tower but shorter than Delhi's 102-metre structure.
The tender was cancelled and there was a lull until 2016, when the AAI revised the proposed tower's height to 112 metres. The reduction in height to 57 metres is mentioned in the last tender floated this January.
On March 22, transport commissioner R. Maity wrote to Jain, forwarding the copy of the ATC Guild's representation. "I am directed to request you to send this department a feedback on the issue raised by the organisation (ATC Guild) at an early date for subsequent transmission of the same to the chief minister's office for information," states the letter.