What happened
On 14 May 2006, a Boeing 777-236, registration G-VIIP, was operating a scheduled passenger flight from Atlanta to London Gatwick. While cruising at FL370, the aircraft encountered a period of unforecast, severe turbulence. At the time of the encounter, the cabin crew were mid-service, and the seat belt signs had only just been activated.
As the aircraft entered a cloud bank, the sudden turbulence caused several occupants to be thrown from their positions. Two cabin crew members were jolted into the air along with a service trolley, and a female passenger, who was unable to reach her seat in time, was also thrown. While the passenger appeared uninjured, the baby she was carrying sustained a broken leg. Following the encounter, the pilots performed an avoiding turn and maintained recommended turbulence penetration speeds. The flight continued to its destination without further incident.
The investigation
The investigation examined the aircraft's flight data recorder and weather information. It was established that there were no prior warnings of turbulence via the Washington World Area Forecast Centre or radio transmissions from other aircraft on the route. The investigation also reviewed the aircraft's radar settings and the physical impact of the turbulence on the airframe and occupants.
Findings
- The aircraft experienced a maximum vertical acceleration of 1.633g and a minimum of -0.023g during the event.
- The turbulence was unforecast and encountered at short range after the aircraft entered a cloud.
- The flight data recorder showed an uncommanded autothrottle disconnection during the period of instability.
- The injuries, which included one broken leg and two minor injuries to crew, were assessed as minor by medical professionals.