Singapore Airlines Flight 321

Singapore Airlines Flight 321

9V-SWM, the aircraft involved in the accident, photographed on 1 February 2021
Accident
Date	21 May 2024 (2024-05-21)
Summary	In-flight turbulence, under investigation
Site	Over Myaungmya District, Myanmar
Aircraft
Aircraft type	Boeing 777-312ER
Operator	Singapore Airlines
IATA flight No.	SQ321
ICAO flight No.	SIA321
Call sign	SINGAPORE 321
Registration	9V-SWM
Flight origin	Heathrow Airport, London, United Kingdom
Destination	Changi Airport, Singapore
Occupants	229
Passengers	211
Crew	18
Fatalities	1
Injuries	104
Survivors	228

On 21 May 2024, a Singapore Airlines Boeing 777-300ER operating as Flight 321, flying a scheduled passenger flight from London Heathrow Airport to Singapore Changi Airport carrying 229 occupants on board, encountered severe turbulence over Myanmar, resulting in 1 death and 104 injuries. The aircraft diverted to Suvarnabhumi Airport in Bangkok, Thailand. The accident was Singapore Airlines' first fatal aviation accident since the crash of Flight 006 in 2000 and the first fatal accident involving the 777-300 series airliner since Emirates Flight 521 in 2016.

Aircraft

The aircraft involved was a 16-year-old Boeing 777-312ER, registered as 9V-SWM, with manufacturer serial number 34578 and line number 701. It was equipped with two General Electric GE90-115B engines and was delivered to Singapore Airlines in February 2008. It was one of two Singapore Airlines Boeing 777-300ERs to be temporarily converted into freighters in 2020, as the airline had tapped into freight as an alternative revenue stream amid depressed passenger demand during the COVID-19 pandemic.

Accident

Route map

The Boeing 777-312ER encountered severe turbulence at around 07:49 UTC on 21 May 2024 (14:19 local time) over the Irrawaddy Basin in Myanmar, around 360 nautical miles (667 km; 414 mi) from Bangkok. Cabin crew members were in the midst of serving breakfast when the turbulence became sufficiently severe for unsecured passengers and objects to become airborne inside the cabin. Some passengers said the "fasten seat belt" sign was turned on too late to prevent injuries. Tracking data showed that the aircraft was at an altitude of 37,000 feet (11,278 m) at the time of the encounter.

One passenger died and 104 others were injured, with 20 of them in intensive care. The sole fatality was a 73-year-old British man travelling with his wife, who was hospitalised. The man was suffering from a heart condition and died from a suspected heart attack. At least five medical personnel, a doctor, a nurse and 3 first aiders, were on board as passengers and tended to the injured despite sustaining injuries during the turbulence. Fifteen Britons, twelve Australians, nine Malaysians, five Filipinos, four New Zealanders, two Singaporeans, and one Hong Konger were also injured. The oldest person to receive treatment was an 83-year old. Most victims were treated for fractures including to the vertebrae and skull, as well as internal damage to the brain, spinal cord and other organs. Images show that the oxygen masks were hanging after parts of the aircraft's interior were damaged.

Preliminary investigations suggested the flight experienced rapid vertical force changes and an altitude drop of around 177 ft (54 m) The flight was then diverted to Bangkok, where it made an emergency landing at 15:45 local time. Singapore Airlines dispatched a relief flight which carried 131 passengers and 12 crew members to Singapore the next morning.

Investigation

Data from both the flight data recorder (FDR) and cockpit voice recorder (CVR) were subsequently obtained by investigators from the Transport Safety Investigation Bureau (TSIB), a department within the Ministry of Transport of Singapore, who arrived in Bangkok on the night of the accident.

The US National Transportation Safety Board was also reported to be sending an accredited representative and four technical advisers to support the investigation process as the accident involved an American-built aircraft.

Preliminary investigations released by TSIB on 29 May 2024 are based on preliminary analysis of the FDR and CVR. These revealed that the turbulence was first encountered at 07:49:21 UTC, the aircraft experienced positive vertical forces fluctuating between 0.44G and 1.57G for about 19 seconds, with an uncommanded increase of aircraft altitude to 37,362 feet (11,388 m). The turbulence caused the plane to vibrate. The autopilot, being engaged, pitched the plane downwards to return to 37,000 feet (11,278 m). There was also an uncommanded increase in airspeed, which the pilots extended the speed brakes to counteract for. At 07:49:32 UTC, one of the pilots called out that the fasten seatbelt signs had been turned on. At 07:49:40 UTC the aircraft experienced a drop in vertical acceleration from +1.35G to -1.5G within 0.6 seconds, which likely caused unrestrained passengers to become airborne. At 07:49:41 UTC the vertical acceleration changed from -1.5G to +1.5G in 4 seconds, which would have caused airborne occupants to fall.

Through this 4.6 second sequence, the aircraft was recorded as dropping from 37,362 feet (11,388 m) to 37,184 feet (11,334 m), a fall of 178 feet (54.3 m). The pilots manually controlled the aircraft for 21 seconds to stabilise the aircraft and re-engaged the autopilot at 07:50:05 UTC. The aircraft returned to its selected altitude of 37,000 feet at 07:50:23 UTC. The uncommanded increase in airspeed and altitude was likely due to an updraft. No further severe turbulence was encountered for the remaining flight to Bangkok.

Aftermath

After the accident, Singapore Airlines announced it would modify its cabin service routines. In addition to the suspension of hot beverage service when the seat belt sign was on, the meal service would also be suspended. The current policy of crew members securing all loose items and equipment in the cabin during poor weather conditions would continue. The airline offered compensation payments of $10,000 to victims with minor injuries and an "advance payment" of $25,000 for those seriously injured as well as further discussions to meet "their specific circumstances". It also offered a full fare refund and S$1,000 to all passengers on board to cover immediate expenses and arrangements for relatives to fly to Bangkok where requested.

On 22 May 2024, the CEO of Singapore Airlines Goh Choon Phong apologized for what happened on Flight SQ321 and expressed condolences while pledging full cooperation with the ongoing investigation. Condolences were also issued by Singaporean Prime Minister Lawrence Wong and President Tharman Shanmugaratnam.

The accident aircraft was subsequently cleared to continue flying, and returned to Singapore on 26 May. It subsequently completed a functional flight check on 23 July in preparation for a return to service. On 27 July, the aircraft returned to service and resumed operations, flying from Singapore to Shanghai as SQ830. A Singapore Airlines spokesperson stated that the aircraft also "met the safety requirements set by the aircraft manufacturer, passed stringent safety checks by SIA’s engineering and flight operations teams, and successfully completed a functional check flight before its return to service."

See also

• China Eastern Airlines Flight 583 (1993)
• United Airlines Flight 826 (1997)
• LATAM Airlines Flight 800 (2024)