Event Details
A flight attendant sustained serious injuries when an airplane encountered convectively induced severe turbulence during cruise flight at 38,000 feet. The operator's meteorology department had properly forecast convective activity in the vicinity of the accident site, and the flight crew indicated awareness of the forecast thunderstorm activity.
Flight Crew Actions
About 19 minutes before the event, the flight received clearance to deviate around an area of scattered thunderstorms. The monitoring pilot then called the lead flight attendant (LFA) on the interphone and advised her to ensure all flight attendants took their seats and remained seated until further notice, as the flight deviated around some weather areas and the deviation should last no longer than 15 minutes. The pilots later reported being back on course and believed they were clear of any weather. They were discussing allowing flight attendants to resume their duties when they encountered a brief area of severe turbulence without warning. Both pilots indicated they were clear of any clouds and well clear of any echoes when the turbulence occurred.
Cabin Crew Communication
The LFA reported that although it had been “bumpy” for most of the flight, when she received the call from the flight deck, it was smooth and the seat belt sign was on. She walked to both galleys and told the flight attendants to be seated for the next 15 minutes. According to the LFA, about 12 to 13 minutes later, the turbulence encounter occurred.
Injuries
The two flight attendants in the aft galley misunderstood the LFA's instructions and believed they had 15 minutes before they were to be seated. Both were standing, completing preparation of their crew meals, and were knocked to the floor during the event. One sustained serious injuries and the other minor injuries.
Turbulence Data
Flight data recorder data indicates that the airplane experienced a vertical acceleration of -0.4 G to +1.8 G, or 2.2 G total change, which corresponds to severe to extreme turbulence.