British Airways B773 near Singapore on Jun 16th 2023, turbulence causes injuries

Last Update: January 11, 2024 / 16:43:25 GMT/Zulu time

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Photo of British Airways G-STBL, Boeing 777-300 — British Airways G-STBL, Boeing 777-300 (Photo credit: HawkeyeUK / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Jun 16, 2023

Classification
Accident

Airline
British Airways

Flight number
BA-12

Departure
Singapore, Singapore

Destination
London Heathrow, United Kingdom

Aircraft Registration
G-STBL

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

A British Airways Boeing 777-300, registration G-STBL performing flight BA-12 (dep Jun 15th) from Singapore (Singapore) to London Heathrow,EN (UK) with 244 passengers and 17 crew, was enroute over the Bay of Bengal at FL300 about 950nm northwest of Singapore when the aircraft encountered turbulence causing injuries to a number of occupants. The crew decided to turn around and return to Singapore where the aircraft landed safely about 2.5 hours later. Two cabin crew received serious, 3 other cabin crew minor injuries.

3 flight attendants received injuries, one head injures when a trolley hit the head, a second received fractures to the ankle, a third serious bruises to her hip.

Passengers reported that food trays and everything loose hit the cabin ceiling and came down again.

The aircraft remained on the ground for about 44 hours, then departed as flight BA-12D.

On Jan 11th 2024 released their final bulletin into this (as well as a second simuliar) occurrence rated an accident concluding the probable cause of the accident was:

Although the pilots of both aircraft were taking action to avoid weather, each aircraft suffered a turbulence event of sufficient severity to cause injuries amongst the unsecured cabin crew. Route weather forecasts give a general prediction that turbulence is likely but often cannot reflect actual conditions in sufficient detail to enable pilots to avoid specific instances of turbulence. G-YMML was approaching its planned destination and so landed there. G-STBL returned to its airfield of departure on receipt of medical advice. The safety of the aircraft was not jeopardised.

The AAIB summarized the sequence of events:

The flight crew had access to a draft version of the flight briefing approximately four hours before they were due to be collected from their hotel in Singapore. The commander stated this allowed all of the pilots to examine the weather forecast at leisure. The crew noted warnings of cumulonimbus cloud (CB) and thunderstorms for the Bay of Bengal.

On the crew transport to the airport the operating co-pilot briefed the crew on the flight and included the weather warnings for the Bay of Bengal. The commander reiterated the forecast of thunderstorms for the first three hours of the flight and said he would turn the seatbelt signs on if necessary. He also stated that if at any time the cabin crew were uncomfortable with the situation in the cabin they should call the flight deck to ask for the seatbelt signs to be illuminated.

The crew arrived at the airport 1 hour and 20 minutes before departure and the pre-flight process was conducted without incident. After departure, the aircraft climbed to a cruise altitude of FL300.

As the aircraft approached the Bay of Bengal, the crew were cognisant of the threat of CB, as forecast in their weather briefing, and were aware that track deviations would probably be required to avoid hazardous weather. Soon after the aircraft entered Chennai airspace the crew heard a company aircraft ahead ask for a deviation of 20 nm left of track. ATC cleared that aircraft to manoeuvre up to 20 nm either side of track. At this point, although the incident aircraft was experiencing only “light chop” (turbulence) and only low intensity returns were visible on the weather radar, the commander switched on the cabin seatbelt signs as a precaution.

It was night and the crew could see flashes of lightning to the left of the aircraft’s track. The aircraft weather radar has the facility to check returns at selected flight levels and the crew did this to assess the risk posed by the weather. Nothing significant was seen. When the crew heard another aircraft ahead request a deviation off track they decided it would be prudent to do the same and requested permission to deviate 20 nm right of track, which was approved by ATC.

The intensity and frequency of the turbulence increased slightly so the commander decided to contact the senior cabin crew member (SCCM). The commander called Door 2L but was told the SCCM was further aft. He stated that he told the cabin crew that it “could be worth sitting down in a few minutes as it could get bumpy.” He then called Door 5L, at the rear of the aircraft, where he found the second most senior cabin crew member. He asked them to pass the message of the bumpy conditions to the SCCM.

Less than two minutes later, at approximately 1730 hrs and with nothing significant visible on the weather radar, the aircraft experienced a severe turbulence episode lasting around 12 seconds. The commander described the situation by saying “There was just too much noise and vibration to take anything in. All I could do for a few seconds was check that the nose was at a safe attitude just above the horizon with wings level and that the engine power was reasonable”. There was a significant display of St Elmos Fire around the cockpit windshields and the stall warning stick shaker was briefly triggered.

At the time of the event the SCCM was in the aircraft’s business class galley and recalled that perhaps only one minute elapsed between the seat belt signs illuminating and the severe turbulence beginning. He saw a crew member across the galley leave the floor and hit the cabin ceiling. The SCCM went across to protect the other crew member from galley carts, which were insecure. The turbulence quickly subsided but the SCCM soon received phone calls from Door 5 to say that there were injuries among the crew. The SCCM informed the pilots of the situation and then went aft to Door 5 and found two crew injured on the galley floor. The crew enacted their medical action plan and were assisted by two doctors from among the passengers who volunteered their support. The doctors were able to use the comprehensive (professional use only) medical kit carried on board the aircraft and administer intravenous pain relief.

The SCCM went to the flight deck and took part in a conference call with the pilots, the contracted medical provider, and the operator’s maintenance control and operations department. The medical provider recommended a diversion on medical grounds and, following discussion, it was decided to return to Singapore. The return to Singapore would be through the same airspace as the outbound flight and so the commander made a public address (PA) to reassure the passengers, but only light turbulence was encountered during the return.

After this decision to return to Singapore was made, the SCCM returned to the cabin. One cabin crew member was seriously injured with an evident fracture of a leg and three others had less significant injuries. The able crew members were redistributed to look after the injured crew and the passengers. At 1920 hrs the crew member who had hit the cabin ceiling began to exhibit symptoms described as a possible concussion by the SCCM. They were given oxygen and another crew member was assigned to look after them. As the planned sector was long there were relief pilots on board and one assisted the cabin crew by manning an exit door for landing. The most seriously injured crew member remained on the floor near the rear of the cabin to avoid moving them to a seat and aggravating their injuries. The aircraft landed in Singapore at 2003 hrs and was met by paramedics and police. The injured crew were taken off the aircraft and transferred to hospital. One crew member was detained in hospital with a fracture to their lower leg. The others were released from hospital but on return to the UK a crew member still suffering issues with a leg injury attended hospital and was also diagnosed with a fracture. Both of the crew members that sustained fractures had been in the vicinity of Door 5 at the rear of the aircraft during the turbulence event.

The AAIB analysed:

The weather forecast provided to the crew indicated the presence of CB in the area of the event and hence, implicitly, the likelihood of moderate to severe turbulence. The aircraft weather radar did not display to the pilots any significant weather returns. However, the pilots could see lighting flashes to the left of the aircraft’s track and heard another aircraft ahead divert to the right of track. At this point, although the turbulence was light the commander switched on the fasten seat belt signs. The commander also decided to divert to the right of track as a pre-emptive measure to avoid the visible weather.

As the intensity of the turbulence increased, the commander called the cabin to tell the cabin crew it “could be worth sitting down in a few minutes as it could get bumpy”. Shortly after this call and with no weather in the vicinity visible on radar, the aircraft experienced a severe turbulence event lasting approximately 10 seconds during which the normal acceleration dipped to 0.7 g and increased to 2.3 g in less than one second. The aircraft stall warner was triggered. The commander described levels of noise and vibration that overwhelmed his senses and left him with limited capacity to control the aircraft. His focus was on maintaining the wings level, keeping the aircraft nose just above the horizon and maintaining a reasonable power setting. The commander’s description of the event is consistent with the descriptor for severe turbulence. The cabin crew were not secure when the event occurred and a number of them were thrown from their feet by the violent motion. The most serious injuries occurred near the rear of the aircraft. The B777 is a long aircraft and motion is more pronounced toward the rear.

The weather information supplied to the crew did indicate an area of CB with the concomitant warning of moderate to severe turbulence. However, the forecast covered a vast area and only forecast isolated thunderstorms.

After the event and with the severity of the injuries evident, the crew consulted with the operator and the operator’s medical provider on options for a diversion and it was decided to return to Singapore.