Airbus A320 232 N632JB incident near Wood, South Dakota

Probable cause

an inadvertent encounter with convective turbulence while in cruise flight.

NTSB analysis

The scheduled passenger flight was enroute at a cruise altitude of flight level 320 (FL320), when the airplane encountered severe turbulence. Of the 2 pilots, 3 flight attendants, and 146 passengers onboard, all three flight attendants and 28 passengers sustained minor injuries. The pilots subsequently diverted to a nearby airport and landed without further incident.

The pilots reported that the onboard weather radar depicted some precipitation along the route, and the captain informed the flight attendants to remain seated and turned the seatbelt sign on. After the flight exited some of the light precipitation, the crew observed cumulonimbus clouds ahead and subsequently requested and were granted a deviation around the clouds; however, the airplane encountered turbulence as it flew through the edge of the clouds. The first officer stated that it "felt like they went up and then dropped," and the captain described the encounter as "very violent and very quick."

The flight attendants reported that the flight had been experiencing light turbulence when the captain called to state that it would continue for the next 30 to 45 minutes. One of the flight attendants made a public address announcement to the passengers to remain seated with their seatbelts on; at this time, all three of the flight attendants were seated in their jumpseats. The turbulence continued for about 10 minutes before it smoothed out, and all three flight attendants got up from their seats to conduct various tasks throughout the cabin. The airplane subsequently encountered what they described as "extreme," "violent" turbulence, and all three sustained injuries.

A review of the flight plan showed convective SIGMETs and thunderstorms that were forecasted and valid on or near the route of flight. The pilots reported that they only saw areas of green returns on their onboard radar and did not see any indication of severe weather. Additionally, there were no pilot reports (PIREPs) to indicate that other aircraft were encountering severe turbulence, nor did air traffic control provide any information to indicate that they might encounter such turbulence.

Text from the NTSB. Open the NTSB docket for DCA16IA215 for the full record.