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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