Rapid gravitational changes caused 178-feet drop of Singapore Airlines jet that hit turbulence

The Boeing 777-300ER aircraft is parked after the SQ321 London-Singapore flight at Bankkok Airport

Rapid changes in the gravitational force led to a 178-feet altitude drop of a Singapore Airlines flight that left one passenger dead and many others who were not buckled up injured in extreme turbulence last week, a preliminary investigation by Singapore’s Transport Ministry said yesterday.

Singapore’s Transport Ministry said investigators, including those from the U.S. National Transportation Safety Board, Federal Aviation Administration and Boeing, had compiled a chronology of events based on the preliminary analysis of the flight’s data and cockpit voice recorders.

Early findings showed the aircraft was passing over the south of Myanmar at 37,000 feet when it began to experience vibration due to changes in the gravitational force, the ministry said. The plane then climbed to an altitude of up to 37,362 feet (11,387 meters) and increased speed possibly due to an updraft, it said. The plane’s autopilot then sought to pitch the jet downwards to its earlier altitude.

“The aircraft experienced a rapid change in G (gravitational force) … this likely resulted in the occupants who were not belted up to become airborne” before falling back down later as the plane rose and fell, the ministry said. “The rapid changes in G over the 4.6 second duration resulted in an altitude drop of 178 feet … this sequence of events likely caused the injuries to the crew and passengers.”

During the turbulence, it said a pilot was heard calling out saying the fasten seat belt sign had been switched on. It said recorded data indicated the pilots manually controlled the plane for 21 seconds to stabilize it before reengaging the autopilot.

The plane made a normal, controlled descent and didn’t encounter further turbulence until it landed in Bangkok almost an hour later, the ministry said, adding that investigations are ongoing.

Passengers have described the “sheer terror” of the aircraft shuddering, loose items flying and injured people lying paralyzed on the floor of the plane.

Twenty-six people remained hospitalized in Bangkok yesterday. MDT/AP