What happened
While operating in the cruise phase of flight, the aircraft encountered severe turbulence. At the time of the encounter, the seat belt signs were not illuminated, and the onboard weather avoidance radar showed no significant weather or convective activity in the immediate area.
Following the turbulence, the captain was notified that passengers had sustained injuries. After assessing the situation, the crew notified Air Traffic Control (ATC) and requested a diversion to an alternate airport. The aircraft subsequently landed at the diversion airport without further incident.
The investigation
A review of the digital flight data recorder (DFDR) was conducted to analyze the flight dynamics during the event. The data revealed that the airplane was subjected to severe acceleration oscillations. Specifically, the vertical acceleration reached peaks of 1.81 g's, -1.38 g's, and 1.99 g's. These oscillations persisted for a duration of 28 seconds.
Additionally, an examination of meteorological data confirmed that there was no area of significant convection present in the vicinity during the period of turbulence.