Gravitational changes, 178-feet drop caused injuries on Singapore Airlines jet that hit turbulence

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 injured in extreme turbulence last week, a preliminary investigation has found

Rapid changes in the gravitational force led to a 178-feet (54-meter) 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 on May 29.

A 73-year-old British man died of a suspected heart attack and dozens were injured after the Boeing 777, which was flying from London’s Heathrow airport to Singapore on May 21, ran into turbulence that hurled people and items around the cabin. The plane, with 211 passengers and 18 crew members, made an emergency landing in Bangkok.

Also read: Why was Singapore flight turbulence severe? | Explained

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 (11,277 meters) 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.