Flying blind: Weather radars fail, pilots look out for clouds

CHENNAI: Cruising at more than 30,000 feet at a speed of more than 700kmph in the middle of night a fortnight ago, the captain and first officer of an Air India's A320 aircraft took turns to look out for patches of clouds on the flight path as the plane's weather radar had conked off. And then, the captain spotted a white patch reflecting moonlight. They diverted the flight just in time to avoid a possible turbulence.

This scenario has been repeating in cockpits of a few Air India flights at night, as weather radars of almost 17 aircraft have been erratic for the last two months. Under pressure to maintain schedules, flight engineers run a test on the ground and clear the aircraft for service.

An Air India official said, "There were problems with weather radars on a few aircraft. Antennas were changed as and when pilots complained. The snag may also be due to change in weather radar technology. The equipment may not be compatible. Several of our old planes have been phased out. Air India will soon get 19 new A320 on dry lease." Director general of civil aviation Arun Mishra told TOI that the matter had not come to his notice.

The weather radar, located inside the nose cone of a plane, sends out microwave pulses to detect rainfall, wet hail, wet turbulence, ice crystals, dry ice and snow. Rain clouds and turbulent areas are displayed on the navigational display unit inside cockpit. Inputs from the radar are used by pilots along with weather reports from meteorological department to navigate.

An adverse weather operations note issued by Airbus says that "any return (of microwaves) at cruise altitude should be considered turbulent. In cruise, any cells (on navigational display in cockpit) with green or stronger return should be avoided by 20 nautical miles."

Experts said the weather radar is a crucial equipment for flights while flying at night to avoid areas of turbulence. Pilots can fly without the radar during the day, but it will be difficult to fly at night without one. "On most days, the sky is cloudy over the Bay of Bengal over which planes on the East Asian routes fly. Similar is the western side of the peninsula which affects flights to Mumbai and Middle East. Flying without a weather radar is tough," a pilot said.

Pilots have filed defect reports pointing out the faulty weather radar, and the airline carried out a few repairs, but the problem recurs. Most of these planes are based in Chennai and Kolkata, and are used on domestic and international routes. "These need to be phased out immediately. The flight engineer cannot run a test on the weather radar on the ground and declare it fit. We have found that equipment go blank on and off while airborne," said the pilot.

One such aircraft was grounded several times by a flight engineer of Singapore Airlines hired by Air India to certify aircraft in Changi airport. In spite of his warnings, Air India has repeatedly used the same plane on the India-Singapore route.

"It is also costing the airline in terms of money and delays because pilots tend to divert the plane on a circuitous route in order to be extra cautious to avoiding clouds. Once a plane had to be diverted way too far from its original route and had to be flown close to Port Blair en route to Kuala Lumpur. More than 15 minutes is lost due to such deviations. This affects turnaround time and may affect schedules," said a source.

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