Flight Information
United Airlines flight 1676, a Boeing 737-724 registered as N23708, was operating as a regularly scheduled passenger flight under 14 Code of Federal Regulations Part 121. The flight departed from Denver International Airport, Colorado, en route to Billings Logan International Airport, Montana, with 120 passengers and crew aboard.
Events Before Turbulence
After a normal departure, the aircraft climbed to a cruising altitude of flight level 380 (FL380). The flight encountered light turbulence, and the crew requested and received clearance to descend first to FL360 and then to FL340. Once the ride smoothed out, the flight crew turned off the seat belt sign.
Turbulence Encounter
At about 1254 mountain standard time, near Kaycee, Wyoming, the aircraft was cruising at approximately FL340 when it entered an area of severe turbulence lasting about 55 seconds. The most intense portion, lasting about 10 seconds, involved vertical accelerations ranging from -1.23 g to +2.05 g, lateral accelerations from -0.27 g to +0.23 g, pitch changes from +5.8° (nose up) to -1.8° (nose down), and roll variations between 14° left and 20° right. Flight data recorder data documented these parameters.
Injuries and Response
During the turbulence, two flight attendants in the forward galley and one in the aft galley were injured. The aft flight attendant lost consciousness and was attended to by passengers with medical training until landing. After being notified of the serious injuries, the flight crew declared an emergency with air traffic control and arranged for medical personnel to meet the aircraft upon arrival at Billings. The three flight attendants were transported to a hospital. One was diagnosed with a fractured fibula; another sustained fractures of the scapula, a rib, cervical vertebrae, and thoracic vertebrae; the third was treated and released with minor injuries. The aircraft sustained no damage.