AIRBUS INDUSTRIE A319-132US AIRWAYS INC

On 15 April 2012, at approximately 0549 coordinated universal time, US Airways flight 496, an Airbus A319-132, N808AW, encountered severe mountain wave turbulence at flight level 320 in the vicinity of Buena Vista, Colorado. Of the 98 passengers and crew onboard, two flight attendants received serious injuries and one passenger received minor injuries during the encounter. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight between Phoenix Sky Harbor International Airport (KPHX), Phoenix, Arizona, and Denver International Airport (KDEN), Denver, Colorado. According to the operator, the captain was the pilot monitoring, and the first officer (FO) was the pilot flying. The flight was cleared to descend from FL390 to 17,000 feet. The seatbelt sign was on during the descent and there were no pilot reports of turbulence in the area.   The captain turned on the weather radar and noted no returns present between the airplane and the airport. As the airplane passed through about FL320, the captain noticed the airspeed rapidly increasing.  He disconnected the autopilot while simultaneously notifying the FO of the overspeed and began to apply a nose-up input. The FO also began to command a nose-up input at that time and so the captain released his pitch up input. The crew received an overspeed warning and then encountered severe turbulence. The flight crew stated the encounter lasted about 10 – 15 seconds. After the encounter, both Elevator and Aileron Computers (ELAC) faults were displayed. The FO resumed pilot flying duties while the Captain performed the appropriate actions to reset ELAC 1 and 2, report the encounter to air traffic control and dispatch, and contacted the flight attendants. The A flight attendant (A-FA) was in the forward jumpseat and the B flight attendant (B-FA) and C flight attendant (C-FA) were in the aft galley sitting in their jumpseats without their seatbelts on. During the turbulence encounter, both aft flight attendants struck the overhead ceiling,  panels before landing on the floor. Two passengers who were also not wearing their seatbelts were lifted out of their seats and struck the ceiling panels during the encounter. Oxygen masks in several rows of seats were also released as a result of the turbulence. Two onboard medical personnel tended to the B-FA and C-FA with the assistance of the A-FA. The captain declared a medical emergency and arranged for emergency personnel to meet the flight on arrival. At the gate, paramedics transported the two injured flight attendants and one of the injured passengers to the hospital.