NTSB Factual Report

On November 30, 2010, about 0935 central standard time, an Embraer EMB-135LR, N12530, operated by Chautauqua Airlines Inc., as flight 1146, encountered turbulence while in cruise about 60 miles south of Milwaukee, Wisconsin. The 2 pilots and 17 passengers were uninjured. The flight attendant sustained a serious injury and nine passengers sustained minor injuries. The airplane sustained no damage. The scheduled domestic passenger flight was conducted under 14 Code of Federal Regulations Part 121. Instrument meteorological conditions prevailed and an activated instrument flight rules flight plan was on file. The flight departed from the Lambert-St Louis International Airport (STL), near St Louis, Missouri, about 0902, and landed at the General Mitchell International Airport, near Milwaukee, Wisconsin, about 1002.

Flight 1146's dispatch package included remarks for significant meteorological information (SIGMET) VICTOR 1, valid until 1130 on November 30, 2010, to include parts of Iowa, Wisconsin, Michigan, Illinois, and Indiana bounded by a line from Marquette, Michigan, to 40 miles south southwest of Sault Ste Marie, Michigan, to Fort Wayne, Indiana, to 50 miles east of St Louis, Missouri, to Quincy, Illinois, to Iowa City, Iowa, to Marquette, Michigan, for occasional severe turbulence between 14,000 feet above mean sea level (MSL) and 24,000 feet. The SIGMET indicated that turbulence was reported by other flightcrews. Remarks indicated that turbulence conditions would continue beyond 1130. The dispatcher issued the dispatch for this flight with a cruise altitude of 13,000 feet MSL and a remark of LOWER [FLIGHT] LEVEL DUE TO TURBURLENCE.

According to the operator, air traffic control (ATC) in STL discussed the potential of turbulence with the flightcrew and stated that an altitude of 15,000 feet MSL would a better option to avoid turbulence than 13,000 feet MSL. ATC briefed that there still could be some turbulence at 15,000 feet MSL. The captain changed the flight's cruise altitude to 15,000 feet MSL. The crew announced the seat belt sign would remain on during the flight due to any potential encounter of turbulence. The seat belt sign was illuminated during the entire flight. During the beginning of the flight attendant's service, the aircraft experienced light turbulence. Halfway through the service, the aircraft experienced moderate turbulence. The flight attendant locked the cart and took a seat. The moderate turbulence dissipated after about one minute and the flight attendant completed the service. Following the completed service, the flight attendant was standing by the forward wardrobe closet and was thrown up into the ceiling and back to the floor. She broke her nose and fractured her left wrist. After that turbulence encounter, the flightcrew called the flight attendant and asked her about her condition and the passenger's condition. She informed the flightcrew of three passengers whom had bumped their heads on the overhead passenger service units and advised the flightcrew of her injuries. Medical personnel were requested who later met the aircraft at the gate.

According to flight data recorder data, approximately 0935, while cruising at a pressure altitude of approximately 15,230 feet and with an indicated airspeed of 317 knots, the airplane's vertical acceleration increased from 1 g to 1.3 g's. The closest recorded latitude and longitude at that time of the upset was 41 degrees 55 minutes 05 seconds north and 088 degrees 18 minutes 46 seconds west. About 0.25 seconds later, the vertical acceleration decreased to -1.2 g's. About 0.63 seconds later, the vertical acceleration increased to 1.8 g's. About one second later, the vertical acceleration decreased to 0.4 g's. During the upset, the pressure altitude increased to a maximum of 15,407 feet and the indicated airspeed increased to 329 knots. Approximately 15 seconds later, the vertical acceleration settled back to 1 g.

A Federal Aviation Administration (FAA) inspector confirmed that all passenger seat belts were fastened. A seated five foot nine inch passenger was observed to have a six-inch gap between the overhead passenger service unit and the passenger's head. Three of the passenger service units sustained damage consistent with the passenger's head impacting the units. None of the passenger lap belt restraints had failed. According to the operator, nine passengers reported minor injuries.

Subsequent to the accident, the operator published an article on turbulence in the airline's quarterly safety newsletter for all employees. In reference to the accident, the operator produced a memorandum on turbulence and the accident event, which was focused on their flight operations personnel.

NTSB Probable Cause

An in-flight encounter with turbulence during cruise flight, which resulted in a serious injury to a flight attendant.