SQ321 passengers endured 62 seconds of turbulence, flight data shows

Granular flight data from flight tracking website Flightradar24 shows that the plane climbed and descended rapidly twice in 62 seconds. - Reuters

SINGAPORE: For one minute and two seconds, passengers of Singapore Airlines Flight SQ321 felt their plane rocked by sudden and extreme turbulence as they flew over the Irrawady Delta region of Myanmar on May 21.

Granular flight data from flight tracking website Flightradar24 shows that the Boeing 777-300ER climbed and descended rapidly twice in 62 seconds, starting from 3.49pm Singapore time, as the plane was nearing the end of a non-stop flight from London to Singapore.

During this time, the plane climbed from its cruise altitude 37,000 to 37,400 feet, and then dropped to 36,975 feet before settling back onto its cruise altitude.

This indicates that it was the rapid transition between the climb and descent caused by the turbulence – and not the actual change in altitude itself, which was relatively minor – that caused pandemonium in the cabin.

The Flightradar24 data – derived from a global network of ground-based receivers, satellites and radars that receive flight data from aircraft transponders – contradicts some earlier reports, which pinpointed the aircraft descending from 37,000 feet to 31,000 feet between 4.06 and 4.10pm as the cause of the injuries.

This latter transition, a commercial pilot told The Straits Times, appears to be the pilots carrying out a controlled descent, most likely to assess the situation before diverting to Bangkok.

The pilot, who has flown both civil and military multi-engine passenger aircraft for more than 20 years and spoke on condition of anonymity, added that the rapid climb would have introduced positive G-forces onto passengers, causing sitting passengers to feel like they have been pinned down in their seats.

The subsequent rapid descent would have resulted in negative G-forces, which would have sent unrestrained passengers and other loose items hurtling upwards onto the ceiling of the cabin, he added.

The embattled plane went through another cycle of rapid climb and descent, causing more damage and injuries, with some passengers and objects hitting the roof panels and overhead lockers then flung back down.

This is reflected in the testimonies of passengers on board SQ321, who reported being thrown onto the cabin roof, with Australian passenger Teandra Tukhunen recounting that she was abruptly woken up when she was thrown to the roof and then to the floor.

The G-forces data would have been captured by the quick access recorder fitted on board the aircraft. This is a flight data recorder designed to provide quick and easy access to raw flight data through means such as USB or mobile phone network.

The Flightradar24 data showed that the Boeing 777 first attained a climb rate of 1,664 feet per minute (fpm) – or 507 metres per minute, double the height of 52-storey Capital Tower – before descending at 1,536fpm six seconds later. It rapidly returned to a climb rate of 900fpm a mere three seconds later, and then descended at 1,536fpm after another 10 seconds.

Transport Minister Chee Hong Tat said on May 24 that investigators from Singapore’s Transport Safety Investigation Bureau are going through data from the cockpit voice recorder and the flight data recorder.

One of the 211 passengers and 18 crew members on board died, and dozens including a two-year-old were injured.

Asked what parents should do to keep their children safe during severe turbulence, the commercial pilot that ST spoke to simply said: “Keep their seatbelts buckled as much as possible.”

He conceded that it was difficult to keep restrained children happy, particularly on long-haul flights, but nevertheless, noted that all passengers needed to be belted in as much as possible throughout a flight.

Aviation experts advise that passengers keep their seatbelts on at all times when seated.

The United States’ National Safety Transportation Board’s data from 2009 to 2018 showed that passengers injured in turbulence-related accidents were most often using, waiting for or walking to or from the toilet. The second-most common group was passengers who were seated but not belted in. - The Straits Times/ANN

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