Flight Attendant Injured by Turbulence During Descent (N650UA)

What happened

The aircraft was operating at flight level 210 when the crew identified thunderstorm cell activity on the onboard weather radar. Air traffic control subsequently issued clearance for the flight to descend to an altitude of 11,000 feet. During this descent phase, the aircraft entered a region characterized by moderate turbulence. The turbulent conditions persisted for approximately 20 to 30 seconds. As a direct result of these aerodynamic forces, a flight attendant lost her balance and fell. She sustained an injury to her ankle from the fall.

Findings

The primary contributing factor was the encounter with moderate turbulence during the descent. The weather radar provided advance warning of convective activity, but the aircraft still penetrated an area of significant vertical wind shear or updrafts/downdrafts associated with the storm cells. This unexpected mechanical stress on the airframe caused unsecured personnel to be thrown from their position, leading to physical injury.