The Airports Authority of India (AAI) has left it to pilots to “exercise caution” while landing at Calcutta airport as an inter-departmental stand-off has delayed the task of scraping dangerous rubber deposits off the primary runway.

“The 19 Left (northern side) runway touchdown zone’s friction effect has reduced. Pilots to exercise caution while landing, specially during the rains,” the AAI said in its advisory to all airlines.

A notice to airmen had been issued last week to remove the rubber from the main runway, but Air Traffic Control set some conditions for closing the strip for repairs. “It will take us some time to meet these conditions,” an official said on Monday.

Till such time, the onus is solely on pilots to ensure that passengers are safe. The advisory states that planes must land at speeds lower than normal and pilots should avoid “excessive braking”.

Metro had reported earlier this month (grab on left) that the roughness essential for plane tyres to grip the tarmac had diminished to below the recommended safety level because of rubber deposits and melting bitumen. The rubber comes from tyres that get heated on contact with the runway. The AAI had planned to close the primary runway for repairs and use the secondary one almost three weeks ago, but red tape came in the way.

Airlines are now being forced to change landing procedures to ensure safety. A large aircraft like an Airbus or a Boeing usually travels at around 250-260kmph while landing. “So, the practice is to rely on maximum braking to bring the aircraft to a halt at the earliest and vacate the runway,” a pilot said.

Reducing the speed means having to burn more fuel, too. “We have had to reduce the speed by raising the flap levels (on the wings of the aircraft) and burning extra fuel in the process,” the pilot said. The flaps regulate the speed of the aircraft while landing. To decrease the speed, an aircraft has to burn 25 to 40 kilolitres of extra fuel during each landing.

On why the runway wasn’t repaired before monsoon set in, an airport official said that wasn’t done because of full passenger load on most aircraft during the first half of the year. “They needed a longer runway for takeoffs and landings. Now, the load factor has declined and the secondary runway can be used comfortably.” Passenger load has been low since mid-May

Sources said it could take another month for repairs to begin.