HISTORY OF FLIGHTOn September 29, 2013, at 0922 Pacific daylight time, a Bombardier DHC-8-402, N449QX, encountered moderate to severe turbulence while on descent for landing to Reno/Tahoe International Airport, Reno, Nevada. The airplane was not damaged. The airline transport pilot, commercial pilot, a cabin attendant and 55 passengers were not injured. One flight attendant was seriously injured, and two passengers received minor injuries. The airplane was registered to and operated by Horizon Air as flight 2441 under the provisions of 14 Code of Federal Regulations Part 121 as a scheduled commercial flight. Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed. The flight originated from Seattle, Washington at 0747.

The flight crew reported that they were aware of strong winds from the west as they were approaching Reno. Air traffic control started the flight's descent earlier than the crew expected; the aircraft was at 25,000 feet. The captain made an announcement to the cabin crew that they needed to be seated as they had already started their descent and that the likelihood of encountering turbulence during the descent was high. This call occurred when the flight was at approximately 22,000 feet. The first officer, non-flying pilot, was communicating with air traffic control who was advising of moderate turbulence in the area below 12,000 feet. The first officer was doing the approach checklist and made a mental note to chime the cabin crew at 14,000 feet for landing. As the flight passed below 12,000 feet the flight had not encountered much turbulence. Then around 10,000 feet as the flight was leveling out, they encountered a series of escalating turbulent jolts, each one lasting a second or two with the strongest categorized as severe. The severe turbulence disconnected the autopilot and the captain took control of the aircraft. The flight crew then called back to the cabin crew to make sure everyone was ok. At this time the flight crew was informed that one flight attendant and 2 passengers needed medical attention. After the severe encounter, the flight continued to encounter occasional moderate turbulence for the remainder of the flight.

The cabin crew consisted of a forward flight attendant A, and aft flight attendant B, who reported that they had finished up with cabin service and were cleaning up the cabin in preparation for descent when they received the landing chime about 15,000 feet.

Flight attendant A was picking up the last of the service items and went to check on the passenger in seat 11B who had already been told twice to buckle his seat belt. She was at row 9 or 10 when the severe turbulence hit. She tried to get to an open seat, but was thrown to the ceiling and hit the overhead bin. The passenger in 11B flew out of his seat and landed on the armrest of 11D which was occupied by a female passenger. Flight attendant A made sure the passenger in 11B got back in his seat then made her way to her jump seat.

Flight attendant B reported that she was in the aft galley and was making the final approach public announcement. As she was getting herself seated and buckling herself into the jump seat, the first of the hard turbulence hit. The turbulence knocked her out of the jump seat onto the floor. At this time the second severe turbulence hit before she was able to get back into her seat. She was thrown up to the ceiling then back down to the floor. A passenger removed himself from his seat and assisted flight attendant B, who was seriously injured, to her seat before he reseated himself. METEOROLOGICAL INFORMATIONA National Transportation Safety Board specialist reviewed the weather conditions for the time of the accident. The conditions indicated a mountain wave event at 10,000 feet mean sea level and for several layers above that. Satellite imagery identified "wavy" clouds; an indication of mountain wave activity and the upper air sounding identified an inversion at 10,000 feet. SIGMET Yankee series was in effect at the time and was issued for severe turbulence the entire day. See docket for additional weather information.

The surface weather report from Reno at 0855 reported the wind from 210 degrees at 19 knots, gusting to 24 knots with few clouds at 8,000 feet, scattered clouds at 10,000 feet and broken clouds at 15,000 feet. An Airmet for turbulence throughout the state of Nevada indicated turbulence, strong winds and low level wind shear that was valid through 0900. Moderate turbulence was indicated between 18,000 feet and 41,000 feet continuing beyond 0900 through 1500.