DCA19CA081

On February 13, 2019 about 1232 PST, Compass Airlines flight 5763, an Embraer ERJ 175, N613CZ, encountered turbulence while in cruise flight at flight level (FL) 340 and subsequently diverted to Reno-Tahoe International Airport (KRNO), Reno, Nevada. Of the 75 passengers and crew onboard, one flight attendant sustained serious injuries while two flight attendants and two passengers received minor injuries. The airplane sustained minor damage. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from the John Wayne-Orange County Airport (KSNA), Santa Ana, California to Seattle-Tacoma International Airport (KSEA), Seattle, Washington. According to the flight crew, about 40 minutes into the flight when the airplane was in smooth air and “between cloud layers”, the captain informed the flight attendants that they could begin cabin service but left the seatbelt sign illuminated for passengers because there was a report of ”occasional light chop”. About 20 minutes later, the flight encountered an area of severe turbulence that lasted about 8 seconds and caused the airplane to rapidly gain altitude and the traffic collision avoidance system (TCAS) to issue a resolution advisory (RA) for opposite-direction traffic 1,000 ft above them. The first officer (FO) , who was the flying pilot, disengaged the autopilot and applied forward control pressure to comply with the RA. The FO could not obtain the target flight path vector directed by the TCAS, so the captain assisted on the controls to obtain the desired pitch attitude. After the airplane descended back to its assigned altitude, the TCAS RA cleared, and the captain informed air traffic control of the turbulence and TCAS RA. According to the flight attendants (FA), the turbulence was encountered as they were beginning the beverage service. Two of the FAs impacted the ceiling before falling to the floor and one passenger, who had been in the lavatory at the time of the encounter had a small head laceration. As a result of the injuries, the captain declared an emergency and the flight diverted to KRNO. The FA in the aft galley was assisted by a medically qualified passenger and remained on the floor until landing due to her injuries. She was transported to the hospital and diagnosed with a broken arm. Post accident examination of the weather satellite data depicted cloud patterns aloft consistent with the presence of a convective updraft coincident with the flight’s location at the time of the turbulence encounter. The convection appeared to be “embedded” with stratiform clouds and may not have been visually identifiable by the flight crew.