SpiceJet flight flew into squall while 3 others deviated left & right

MUMBAI: Even as the SpiceJet flight from Mumbai to Durgapur flew into severe turbulence on Sunday, injuring 17 onboard, at least three other flights that were routed to fly over the same region had deviated and opted for longer routings to avoid the violent squall line of ‘Kalbaisakhi’ thunderstorm cells, reports Manju V.

The SpiceJet accident was the third such pre-monsoon turbulence associated with Kalbaisakhi in the past few years that resulted in serious injuries to flyers. Others that deviated included IndiGo flights from Ahmedabad and Chandigarh — both bound for Kolkata — and a SpiceJet flight from Delhi to Hanoi, Vietnam. Satellite images show a line of thunderstorm cells tracing a C-shaped pattern from Gaya down to Ranchi and Jamshedpur.

A pre-monsoon weather phenomenon, Kalbaisakhi brings torrential rain or severe thunderstorm with dark clouds and gale-speed winds. Following Sunday’s incident where a SpiceJet Mumbai-Durgapur flight ran into turbulence, the airlines issued a statement saying, “The weather radar on this aircraft did not have issues. The aircraft had operated four sectors prior to this sector on May 1. This weather radar has a manual tilt setting to allow the pilot to set the tilt function as per the flight profile.

Pilots use manual tilt to check the weather above and below their flight path. This feature is common to all weather radars, including the latest models. Pilots are welltrained to use this function and do so regularly and effectively every day to avoid areas of bad weather (turbulence). They have been doing so for years. ”

However, a Honeywell document on next-generation weather radar states that manually-operated radar require pilots to undergo detailed training and gain experience to be effective. “These ‘tilt-based radar systems’ are labour-intensive, requiring the pilot to make complex geometric calculations… When the workload is heavy, it is possible to adjust the radar incorrectly or misinterpret the data. ”

Capt Amit Singh, an air safety expert, said, “No pilot would knowingly enter a thunderstorm cell, especially one associated with Kalbaisakh. ” Asource said, “A number of flights deviated to the left and right of this squall line. The SpiceJet flight from Delhi to Hanoi goes over Kolkata and that aircraft, too, deviated. Apparently, the pilots of that flight had informed pilots of the Durgapur SpiceJet flight that every other flight was deviating. ”

Pilots believe that the manually operated older generation weather radar on the SpiceJet Boeing 737-800 aircraft, VT-SLH, played a crucial role in sending the aircraft into turbulence. “About nine aircraft in the SpiceJet Boeing 737 fleet, including the one involved in the accident, are fitted with the old manual operating Honeywell weather radar,” said a source.