One person is dead and dozens have been injured after Singapore Airlines flight SQ321 experienced severe turbulence over Myanmar. The Boeing 777-300ER was operating from London to Singapore when it encountered turbulence at approximately 07:49 UTC on 21 May (14:19 local time). There were thunderstorms, some severe, in the area at the time.
The flight departed London at 21:38 UTC (22:38 local time) on 20 May proceeding southeast toward Singapore. Based on ADS-B data sent directly from the aircraft, at approximately 07:49 UTC on 21 May, the flight encountered a rapid change in vertical rate, consistent with a sudden turbulence event. At 08:03 UTC the aircraft changed course and began a diversion to Bangkok. SQ321 landed in Bangkok at 08:45 UTC (15:15 local time), where it was met by medical personnel.
Flightradar24 data
After processing the high-frequency ADS-B data for SQ321 and correlating the possible event time with media reports, we believe the turbulence event occurred at 07:49 UTC. In normal flight, some small variation in vertical rate is expected, however, at 07:49:24Z.824 the first ADS-B frame with an increased vertical rate is received by our network. There are unexpected changes to the vertical rate for nearly one minute before returning to 0 feet per minute.
Some media reports have erroneously reported the pilots’ initial descent toward Bangkok from 37,000 feet to 31,000 feet as the turbulence event. While the aircraft may have continued to experience turbulence during that descent, it was a standard descent to a new flight level controlled by altitude selection in the aircraft’s autopilot.
Data available for download
Three separate files are available for download. The standard format CSV and KML files each contain data for the entire flight at our standard reporting frequencies. The granular CSV contains all network processed data from 07:00 UTC until the aircraft turned off its transponder in Bangkok.
Aircraft information
Flight SQ321 was operated by a Boeing 777-300ER registered 9V-SWM (MSN 34578). It is powered by two GE90-115B engines. The aircraft was delivered new to Singapore Airlines in February 2008.
Investigative updates
Singapore’s Transport Safety Investigation Bureau has released its preliminary report on Singapore Airlines flight SQ321. The TSIB has completed processing of the data from the aircraft’s flight data recorder. Investigators found that the aircraft experienced an uncommanded increase in altitude and “an uncommanded increase in airspeed which [the pilots] arrested by extending the speed brakes.”
Further, “At 07:49:40 hr, the aircraft experienced a rapid change in G as recorded vertical acceleration decreased from +ve 1.35G to negative (-ve) 1.5G, within 0.6 sec. This likely resulted in the occupants who were not belted up to become airborne.”
One second later, “the vertical acceleration changed from -ve 1.5G to +ve 1.5G within 4 sec. This likely resulted in the occupants who were airborne to fall back down.”
The aircraft’s altitude was restabilized at 37,000 ft at 07:50:23.
