Introduction
The UK Air Accidents Investigation Branch (AAIB) reported two turbulence events involving Boeing 777 aircraft in June 2023. Both flights encountered unexpected turbulence that resulted in injuries to cabin crew, despite pilots taking measures to avoid adverse weather.
Incident 1: G-STBL
On 15 June 2023, a Boeing 777-336ER (registration G-STBL) departed Singapore en route to London. The aircraft, powered by two General Electric GE90-115B turbofan engines, had 17 crew and 244 passengers on board. The commander, aged 49, had 17,678 total flying hours including 1,662 on type.
Approximately 1 hour 50 minutes after departure, while entering the Bay of Bengal at night, the crew were aware of forecast thunderstorms. They observed lightning flashes and saw low-intensity returns on the weather radar. After hearing other aircraft request deviations, they obtained clearance to deviate 20 nm right of track. The seatbelt signs were switched on as a precaution due to light chop.
Less than two minutes after a cabin crew briefing about bumpy conditions, the aircraft encountered severe turbulence lasting about 12 seconds. The commander described intense noise and vibration; the stall warning stick shaker was briefly triggered, and St Elmo's Fire was visible on the cockpit windshields. Unsecured cabin crew were thrown around; one crew member hit the cabin ceiling. Two crew members sustained serious injuries (fractured legs), and three had minor injuries. Doctors among the passengers assisted with medical care, including intravenous pain relief.
The crew decided to return to Singapore, where the aircraft landed at 2003 UTC. Paramedics met the aircraft and the injured were taken to hospital. One crew member was hospitalized with a lower leg fracture; another was later diagnosed with a fracture after returning to the UK.
Incident 2: G-YMML
On 28 June 2023, a Boeing 777-236 (registration G-YMML) was approaching Beijing Daxing International Airport. The aircraft, powered by two Rolls-Royce RB211 Trent 895-17 turbofan engines, had 13 crew and 239 passengers. The commander, aged 59, had 19,682 total flying hours including 9,902 on type.
About 25 minutes before landing, the commander switched on the fasten seatbelt signs due to convective weather on the radar. A public address was made 20 minutes before landing. The aircraft encountered occasional light turbulence, which became continuous during descent. Air traffic control provided radar vectors to avoid weather, resulting in a longer arrival. The commander described the turbulence as occasional moderate chop.
After landing, the senior cabin crew member informed the commander that one crew member had injured an ankle during the turbulence. The injury occurred when the crew member fell in a passenger aisle. The injured crew member was relocated to a passenger seat, and another crew member took over their door duties. Many passengers were sick during the approach. Paramedics met the aircraft at the gate and immobilized the injured ankle.
Aftermath
Both incidents highlight that despite flight crew awareness of weather forecasts and proactive measures such as seatbelt sign activation and track deviations, turbulence of sufficient severity to injure unsecured cabin crew can still occur. The AAIB report noted that when route weather forecasts cover large areas with general turbulence predictions, pilots may not be able to identify specific areas where turbulence will be encountered.