Incident
On March 3, 2012, at approximately 1720 eastern standard time, Air Wisconsin flight 3733, a Bombardier CL-600-2B19 (registration N453AW), encountered severe clear air turbulence while descending into Philadelphia International Airport (PHL) in Philadelphia, Pennsylvania. The flight was operating under 14 CFR Part 121 as a regularly scheduled passenger service from Cleveland Hopkins International Airport (CLE) to PHL, carrying 50 passengers and crew.
Sequence of Events
According to the flight crew, as the aircraft descended through about 17,000 feet, it initially experienced light turbulence, prompting the crew to turn on the seatbelt sign. Shortly thereafter, the aircraft encountered severe clear air turbulence that caused it to drop at least 300 feet.
Injuries and Response
At the time of the turbulence, a flight attendant was in the galley securing the beverage cart. The violent motion threw her to the ceiling and then to the floor, injuring her back. A passenger assisted the flight attendant into her jumpseat. The flight crew declared an emergency with air traffic control and requested that emergency personnel meet the aircraft at the gate. After landing, the flight attendant was transported to a hospital and diagnosed with a fracture of her L-1 vertebrae. The aircraft was not damaged.