Extreme turbulence caused Singapore Airlines plane to plummet 54m in less than five seconds

The interior of the cabin is pictured after an emergency landing at Bangkok's Suvarnabhumi International Airport
The interior of the cabin after an emergency landing at Bangkok's Suvarnabhumi International Airport - Reuters

A Singapore Airlines plane that was forced to make an emergency landing after extreme turbulence last week plummeted 178ft (54 metres) in less than five seconds, an investigation has revealed.

Travellers who did not have their seatbelts fastened “became airborne” when Singapore Airlines flight SQ321 entered a “sudden extreme turbulence”.

The Boeing 777-300ER was travelling over Myanmar at 37,000ft when the incident happened, sending many of the 211 passengers and crew aboard it into the air - and slamming some into the plane’s ceiling.

British grandfather Geoffrey Kitchen, 73, died on the flight after suffering a heart attack.

From beginning to end, the incident lasted just 57 seconds, Singapore’s transport ministry said in a preliminary investigation report published on Wednesday.

Accident investigators said that an “uncommanded increase in aircraft altitude” followed by a sudden drop of tens of metres “likely resulted in the occupants who were not belted up to become airborne”.

The sudden climbs and descents caused immediate changes in gravitational force (G-force) felt by passengers, hurling them around the cabin.

“The rapid changes in G over the 4.6 seconds duration resulted in an altitude drop of 178 ft (54 m), from 37,362ft to 37,184ft. This sequence of events likely caused the injuries to the crew and passengers,” the report continued.

Unexpected vibrations, followed by further unexpected altitude and airspeed changes, were the first signs available to the pilots that they were encountering turbulence, the report said.

“While managing the airspeed ... it was heard that a pilot called out that the fasten seat belt sign had been switched on,” it continued.

“The aircraft experienced a rapid change in G as recorded vertical acceleration decreased from +ve 1.35G to negative (-ve) 1.5G, within 0.6 sec,” continued the ministry.

The forces involved meant a person weighing 84kg - just over 13 stone - would have briefly felt as if they weighed 113kg, or almost 18 stone.

“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,” said the ministry, citing information extracted from the Boeing’s flight data and cockpit voice recorders.

The pilots of the London to Singapore flight diverted to Bangkok, Thailand, in the immediate aftermath of the severe turbulence, landing 45 minutes after the incident.

The aircraft parked one day after an emergency landing at Suvarnabhumi International Airport in Thailand
The aircraft parked one day after an emergency landing at Suvarnabhumi International Airport in Thailand - RUNGROJ YONGRIT/EPA-EFE/Shutterstock

Adinun Kittiratanapaibool, director of Bangkok’s Samitivej Srinakarin Hospital, later said his staff were treating six people for skull and brain injuries, 22 for spinal injuries, and 13 for bone, muscle and other injuries.

“We have never treated people with these kinds of injuries caused by turbulence,” he told reporters.

Passengers described scenes of chaos in the minutes after the incident, with photos of the cabin showing dents in the overhead cabin panels, as well as oxygen masks and panels hanging from the ceiling.

Singapore Airlines said it acknowledged the report and was cooperating fully with the investigation.

The airline said on Wednesday that 42 people who were aboard the flight were still in Bangkok more than a week later, including 26 passengers receiving medical treatment in hospital.

Josh Silverstone, a 24-year-old Briton on his way to the Indonesian holiday island of Bali, told reporters: “I fell onto the floor, I didn’t realise what happened. I must have hit my head somewhere. Everyone was screaming on the plane. People were scared.”

The investigation team comprised Singaporean investigators together with representatives from aircraft maker Boeing, the US National Transportation Safety Board and the US Federal Aviation Administration.