Passengers on Singapore Airlines flight experienced rapid g-force changes

The Singapore Airlines flight that encountered severe turbulence last week dropped 178ft in fewer than five seconds with passengers experiencing rapid changes in g-force, according to a preliminary investigation.

Changes in vertical acceleration, measured as gravitational force equivalent (g-force), over 4.6 seconds, “likely caused the injuries to the crew and passengers”, according to a chronology of events compiled by the investigations body of Singapore’s ministry of transport, the National Transportation Safety Board, the Federal Aviation Administration and Boeing.

One person died and dozens were hurt when Flight SQ321 from London to Singapore on May 20 experienced sudden extreme turbulence over the Irrawaddy basin in Myanmar. The flight was diverted to land in Bangkok, Thailand.

Some passengers suffered severe spinal and brain injuries and as of Tuesday, 26 were still receiving medical treatment in Bangkok.

The report, based on data from the aircraft’s black box flight recorder, said it had likely been flying over an area of developing thunderstorms at 37,000ft when the turbulence hit.

The flight underwent an “uncommanded” increase in altitude and airspeed while the autopilot was switched on, which the report said was most likely due to the aircraft being hit by a rapid upward movement of air, which lifted it more than 360ft.

In response, the autopilot pitched the aircraft back down towards the planned altitude of 37,000ft and the pilots applied the brakes, the report said.

Passengers on board would have felt a “rapid change in G [force]” as the vertical acceleration of the aircraft changed, likely throwing people not wearing seatbelts into the air and then back down again, the report said.

These abrupt changes over 4.6 seconds resulted in an altitude drop of 178ft.

Overall the incident lasted just over a minute before the flight returned to its planned altitude.

Singapore Airlines acknowledged the preliminary investigation findings and said it was “fully co-operating with the relevant authorities in the ongoing investigations”.  

The airline is covering passengers’ medical and hospital expenses, as well as any additional assistance.

Singapore’s ministry of transport said an investigation by the Transport Safety Investigation Bureau of Singapore was ongoing.

Turbulence is becoming more common as climate change affects weather patterns and the earth’s atmosphere. However, it is rarely severe enough to disrupt flights or injure passengers, and modern aircraft are designed to handle it without structural damage.

Incidents of severe clear-air turbulence in the north Atlantic, one of the world’s busiest flight paths, has increased 55 per cent since 1979, according to Paul Williams, a professor of atmospheric science at the University of Reading.

His forecasts show that this type of turbulence, which does not show up on weather radars and can hit without warning, will double or even triple in some parts of the atmosphere in the coming decades.

The Singapore Airlines incident was followed by another days later involving Qatar Airways. Twelve people were injured as a result of turbulence during a flight from Doha to Ireland on May 27.