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Grooving can prevent aircraft from slipping

Three flights were diverted and many delayed by hours at the Indira Gandhi International Airport on Thursday due to congestion after heavy rain. The heavy showers made the main runway so slippery that it had to be closed, adding to the chaos. Sidhartha Roy reports.

delhi Updated: Aug 21, 2010 01:19 IST
Sidhartha Roy

Three flights were diverted and many delayed by hours at the Indira Gandhi International Airport on Thursday due to congestion after heavy rain. The heavy showers made the main runway so slippery that it had to be closed, adding to the chaos.

The mayhem could have been avoided had the airport operator, Delhi International Airport Ltd (DIAL), followed a technique that makes the runway rain proof — grooving.

Pilots on Thursday complained the main runway 11/29 had become wet and slippery.

Rubber deposits on the runway made it slippery during the rain. The runway was closed between 9:30 a.m. and 11 a.m. to clear the deposits and again from 3:30 p.m. to 5 p.m. for regular maintenance, affecting flight operations.

Grooves on the runway increase the friction level and ensure aircraft don’t skid after landing. A runway usually becomes slippery after 3 mm of rain. The thin grooves, 6 mm deep, are engraved into the runway surface and allows water to dissipate. The water flows into the grooves. The peaks between the grooves remain in contact with the aircraft wheels.

Runway 29/11 does have grooves, but only on both ends and not at the middle, where aircraft actually land. Grooves were cut on the runways ends made of concrete but not at the middle section built with asphalt.

Earlier, the DIAL had said grooving on the asphalt section will be carried out later. But now the operator is saying grooving on the asphalt portion is not a "desirable practice".

In a statement, the DIAL said that such grooves tend to close very quickly, affecting the riding quality of the runway surface. This results in excessive wear of the aircraft tyres and causes water to fill in the grooves during the rainy season. The ultimate result: a steady deterioration of the entire runway, DIAL said.

Experts have a different take. "Grooved runways provide double the friction during landing than a normal runway," said air safety expert Captain A Ranganathan.

"Both concrete and asphalt runways can be completely grooved without any problem."