A Singapore Airlines flight hit by severe turbulence experienced a rapid change in gravitational force and a 54m (178ft) altitude drop in four seconds, an investigation has found.
It comes after a 73-year-old British man died from a suspected heart attack after the incident on 21 May on the London-Singapore flight.
Dozens more were injured after passengers described people being “launched into the ceiling” and overhead lockers – with 28 people still in Thai hospitals after making an emergency landing.
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The Transport Safety Investigation Bureau said: “The vertical acceleration changed from negative 1.5G to positive 1.5G within 4 seconds. This likely resulted in the occupants who were airborne to fall back down.”
It added: “The rapid changes in G over the 4.6 seconds duration resulted in an altitude drop of 178ft (54m), from 37,362 ft to 37,184ft. This sequence of events likely caused the injuries to the crew and passengers.”
Last week, Singapore Airlines said the pilot declared a medical emergency and landed in Bangkok after “sudden extreme turbulence over the Irrawaddy Basin at 37,000ft about 10 hours after departure”.
The 73-year-old who died during the incident was later named as Geoff Kitchen, from Thornbury near Bristol. He was on a six-week holiday with his wife to Singapore, Indonesia, and Australia at the time.
Passenger Dzafran Azmir, 28, described the chaos on board.
“Suddenly the aircraft starts tilting up and there was shaking so I started bracing for what was happening,” he said.
“And very suddenly there was a very dramatic drop so everyone seated and not wearing seatbelts was launched immediately into the ceiling.”
“Some people hit their heads on the baggage cabins overhead and dented it,” he added.
“They hit the places where lights and masks are and broke straight through it.”
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‘I remember waking up on the floor’
Hong Kong’s Greater Bay Airlines said on Wednesday it would require passengers to fasten their seatbelts at all times during flights, even when the seat belt sign is off, starting from Thursday.
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The company said it’s not a mandatory requirement but a precautionary measure for passenger safety.
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Singapore Airlines said it acknowledged the report and was cooperating fully with the investigation.