Incident Overview
An airplane, while descending from FL410, received an amended ATC clearance to FL270 for a better ride. After leveling off at FL270, approximately 25 nautical miles east of Grand Rapids, Michigan, the aircraft experienced sudden moderate turbulence. A passenger who was exiting the lavatory at that time fell and sustained serious injuries.
Flight Crew Actions
The flight crew reported that the weather radar did not display any weather on the 80-mile scan. The seat belt sign had been illuminated about five minutes before the turbulence encounter, and the captain made an announcement for passengers to expect "bumps" on the approach.
Lavatory Equipment
The airplane's lavatories are equipped with a public address speaker, a flight attendant call button, and a "return to seat" sign that illuminates when the cabin seat belt sign is activated.
Weather Information
Company dispatch/weather department data indicated that the airplane had been flying in an area of 3/10ths coverage of level three and four thunderstorms.