On March 3, 1999, about 1530 Eastern Standard Time, a flight attendant was seriously injured when a Saab 340A, N343BE, operating as Business Express flight 6277, encountered turbulence about 40 nautical miles northeast of Atlantic City, New Jersey. The airplane was not damaged, and the 2 pilots and 30 passengers were uninjured. Instrument meteorological conditions prevailed at the time of the accident. An instrument flight rules flight plan was filed for the flight between General Edward Lawrence Logan International Airport (BOS), Boston, Massachusetts, and Philadelphia International Airport (PHL), Philadelphia, Pennsylvania. The scheduled passenger flight was conducted under 14 CFR Part 121. According to a Business Express accident/incident irregularity report, the seat belt sign was turned on, the flight attendant had returned to her jumpseat after conducting a walk-through, and she was "waiting for the 10 out call." She was not belted in at the time. The airplane encountered turbulence, and the flight attendant was thrown from her seat. Her head hit the ceiling of the airplane, and when she came down, she hit her back on the jumpseat, which had retracted. She remained on the deck until after the airplane's arrival at the gate, when she was evacuated by emergency medical personnel. The captain stated that the severe turbulence was unexpected, and that the weather radar was on and operating normally. There were no reports of turbulence along the route of flight, and the flight had been smooth both before and after the turbulence event. According to the Safety Board Flight Data Recorder Factual Report, the accident occurred over a period of 20 seconds, while the airplane "was descending through approximately 8,000 feet and apparently in a turn from 260 degrees to 245 degrees." During the event, pitch oscillated between nose down 0.18 degrees and nose down 3.34 degrees, and left roll reached a maximum 16.17 degrees. Propeller speeds also oscillated during that timeframe. Vertical, lateral and longitudinal acceleration parameters for the recorder were not operating properly.