Singapore turbulence flight investigation finds sharp altitude drop caused injuries

Singapore: Preliminary findings of an investigation into a Singapore Airlines flight hit by severe turbulence last week showed a rapid change in gravitational force and a 54 metre altitude drop caused injuries, Singapore's transport ministry said on Wednesday.

One passenger died of a suspected heart attack and dozens were injured after Singapore Airline Flight SQ321, flying from London to Singapore, encountered what the airline described as sudden, extreme turbulence while flying over Myanmar. The ministry said the investigation was ongoing.

The SQ321 London-Singapore flight on a Boeing 777-300ER plane carrying 211 passengers and 18 crew diverted to Bangkok for an emergency landing after the plane was buffeted by turbulence that flung passengers and crew around the cabin, slamming some into the ceiling.

"The aircraft experienced a rapid change in G (gravitational force) ... This likely resulted in the occupants who were not belted up to become airborne," the ministry said in a statement, citing a report by the Transport Safety Investigation Bureau of Singapore.

"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.

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

The report also said a pilot was heard calling out that the fasten seat belt sign had been switched on.