SQ321 turbulence: 'Rapid' G-force changes, altitude drop likely caused injuries to unbelted passengers, crew

Preliminary investigations into the severe turbulence on Singapore Airlines flight SQ321 have showed that "rapid" changes in gravitational force (G) - up to three times that of Earth's - and an altitude drop of around 54m likely caused injuries to passengers and crew who were not belted up.

The aircraft then experienced a rapid change in G, 19s after the initial vibrations, as recorded vertical acceleration decreased from positive 1.35G to negative 1.5G, within 0.6s.

“This likely resulted in the occupants who were not belted up to become airborne,” said MOT. 

Just one second later, the vertical acceleration changed from negative 1.5G to positive 1.5G, within 4s. “This likely resulted in the occupants who were airborne to fall back down,” said MOT. 

The rapid changes in G over the 4.6 sec duration resulted in an altitude drop of 178 ft, from 37,362 ft to 37,184 ft.

“This sequence of events likely caused the injuries to the crew and passengers,” said MOT. 

In the midst of the sequence of rapid changes in G, recorded data “indicated that the pilots initiated control inputs to stabilise the aircraft, disengaging the autopilot in this process”. 

Info courtesy CNA https://www.channelnewsasia.com/singapore/sq321-turbulence-investigation-findings-g-force-4370916?cid=internal_sharetool_androidphone_29052024_cna