On 21st May 2024, Singapore Airlines (SIA) flight SQ321 from London Heathrow Airport (LHR) to Singapore Changi Airport (SIN) encountered extreme turbulence. This resulted in several injuries and the death of one man. The Transport Safety Beureau of Singapore has released its initial findings. I take a look at what they found.
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The Transport Safety Investigation Beureau of Singapore (TSIB) extracted the flight data recorder and cockpit voice recorder from the aircraft and released their preliminary analysis but they state that investigations are ongoing. It is worth noting that the TSIB is working alongside United States representatives for the FAA, the NTSB and Boeing.
The data confirms that SQ321 was a normal flight prior to encountering the turbulace.
At 07:49:21 UTC on 21st May 2024, the aircraft was flying at 37,000 feet over the south of Myanmar. The preliminary analysis states that the graviatational force was recorded as fluctuating between positive 0.44G and positive 1.57G for 19 seconds with the report stating that this would have caused the aircraft to experience slight vibrations.
However at the same time, an uncommanded increase in the aircraft altitude was recorded, reaching a maximum height of 37,362 feet. In response, the autopilot pitched the nose of the aircraft down in order to descend to the selected altitude of 37,000 feet. The report states that the pilots noticed an uncommanded increase in airspeed and extended the speed brakes. The report suggests that the increase in altitude and airspeed was likely due to the aircraft being acted on by the upward movement of air.
The report continues and states that at 07:49:40 UTC, the aircraft experienced "a rapid change in G" with recorded vertical acceleration changing from positive 1.35G to negative 1.5G in 0.6 seconds. The reports suggests that "This likely resulted in the occupants who were not belted up to become airborne."
The report states that at 07:49:41 UTC the vertical acceleration of the aircraft changed from negative 1.5G to positive 1.5G in 4 seconds with the analysis concludng that this would have resulted in airborne passengers falling down.
During this rapid change in G force over the 4.6 seconds, the report states that the aircraft dropped 178 feet from 37,362 feet to 37,184 feet with this period of time likely causing injuries to crew and passegers.
The data indicates that the pilots, in an attempt to stabilise the aircraft, disengaged the autopilot and manually controlled the aircraft for 21 seconds.
The report states that the vertical acceleration fluctuated over the next 24 seconds from positive 0.9G to positive 1.1G before the aircraft returned to 37,000 feet at 07:50:23 UTC.
The analysis states that the pilots were informed by cabin crew of injured passengers and decided to divert to Bangkok Suvarnabhumi Airport in Thailand, requesting medical services to meet the aircraft on arrival. The data shows that around 17 minutes after experiencing turbulance the pilots decended to 31,000 feet and touched down at BKK at 08:45:12 UTC.
Date and Time (UTC) | Event |
20 May 2024, 21:38 | Flight SQ321 departed LHR |
21 May 2024, 07:49:21 | The aircraft was passing over the south of Myanmar at 37,000 feet. The G force fluctuated between +0.44G and +1.57G for 19 seconds. At the same time as the start of the vibrations the aircraft altitude increased to 37,362 feet. The autopilot pitched the nose of the aircraft down to descend to 37,000 feet. The pilots noticed an increase in airspeed and extended the speed brakes. |
07:49:32 | Pilot called out that the fasten seatbelt sign had been switched on. |
07:49:40 | The aircraft experienced a rapid change in G force from +1.35G to -1.5G within 0.6 seconds |
07:49:41 | Vertical acceleration changed from -1.5G to +1.5G within 4 seconds |
07:50:05 | The pilot reengages the autopilot after having manually controlled the aircraft for 21 seconds |
07:50:23 | The aircraft returned to 37,000 feet after experiencing fluctuations from +0.9 G to +1.1 G for 24 seconds |
08:06:51 | The pilots initiate a normal descent from 37,000 feet to 31,000 feet |
08:10:00 | The aircraft reached 31,000 feet |
08:45:12 | The aircraft touched down at BKK, Thailand |
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