Incident Overview
A captain reported that approximately 20 minutes into a smooth flight, and about 10 minutes before landing, he felt some light chop and turned on the seat belt sign. Shortly thereafter, the aircraft encountered sudden and violent severe turbulence, which seriously injured a flight attendant.
Crew Actions
At the time of the turbulence, the flight attendant had completed her service and was about to acknowledge the seat belt sign over the public-address system prior to being seated for landing. The captain had activated the sign in response to the light chop.
Weather Information
According to the crew, no valid SIGMET was issued, and no AIRMET or PIREPS were available regarding the turbulence encountered.
