Passengers and the air travel industry are likely to take a long time to recover from the shock caused by last week's Singapore Airlines flight, which experienced turbulence that caused one death and dozens of hospitalizations.
But most of the damage was caused in less than five seconds, according to a preliminary investigation by Singapore's Transport Safety Investigation Bureau.
A summary of the inquiry's initial findings, released this Wednesday, revealed that a severe change in gravitational force, which took just 4.6 seconds and resulted in a 55-meter loss of altitude, “probably caused the injuries to the crew and passengers”.
Singapore Airlines flight SQ321, which was traveling from London to Singapore on May 20 with 211 passengers and 18 crew members, was flying normally until it passed over southern Myanmar at an altitude of 37,000 feet and began to feel a “slight vibration”.
For about 19 seconds, according to Time magazine, while the plane encountered this initial turbulence, probably caused by a rising air current, it climbed “uncommanded” about 110 meters - a movement that the autopilot tried to correct by tilting the plane downwards.
At the same time, the pilots observed an “uncommanded” increase in air speed, to which they responded by extending the speed brakes. The report adds that, at this point, “a pilot was heard to say that the fasten seatbelt sign had been activated”.
About eight seconds later, the plane experienced a “rapid change” in gravitational force (G), as the recorded vertical acceleration decreased from +1.35G to -1.5G in the space of 0.6 seconds.
“This probably caused the occupants who were not wearing their seatbelts to be suspended in the air,” says the report.
Over the next 4 seconds, the gravitational force changed again from -1.5G to +1.5G, which, according to the report, “probably caused the occupants who were in the air to fall again”. At the end of the 4.6-second period of drastic G changes, the plane had fallen to an altitude of 11,000 meters.
The pilots tried to stabilize the plane, which continued to experience more turbulence, although less intense, by “disengaging the autopilot” and “controlling it manually” for 21 seconds, before the plane returned to its normal altitude, about a minute after the initial turbulence.
About 17 minutes later, after it was ascertained that there were injured people who needed medical attention, the pilots began descending the plane for an emergency landing at Thailand's Suvarnabhumi airport.
On Wednesday, 42 passengers who were on board the flight are still in Bangkok, including 26 who are still receiving hospital treatment, Singapore Airlines said in a statement.
Investigations are still ongoing.
In a separate statement, Singapore Airlines, which has previously announced that it is reviewing its in-flight seatbelt policy, said that it “acknowledges” the preliminary findings of the transport safety department and is “cooperating fully” with all relevant authorities.
In recent years, turbulence incidents have caused dozens of injuries - among others, on Air Canada, Hong Kong Airlines and Malaysia Airlines flights, and on a Mauritius-Madrid flight contracted by a tour operator.
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In February, Austrian startup Turbulence Solutions announced a Turbulence Cancellation system capable of reducing the waves of turbulence felt by passengers by more than 80%, could potentially eradicate all turbulence and bring smoother flights.
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