Incident Overview
A commercial flight experienced unforecasted clear air turbulence while flight attendants were providing meal service to passengers. The turbulence caused several flight attendants to be thrown to the floor. One flight attendant operating in the rear of the aircraft sustained a fractured left shoulder.
Pilot Reports
The autopilot was engaged at the time of the event, and there were no pilot inputs during the turbulence encounter. According to statements from the captain, who was the flying pilot, and the first officer, the clear air turbulence lasted 3 to 4 seconds. The captain characterized the turbulence as "moderate" and noted that it felt similar to a wake turbulence encounter due to its extremely short duration.
Environmental Conditions
The captain indicated that there were no aircraft ahead of them and that the nearest thunderstorms were greater than 20 miles to the northwest. The first officer added that they had received no turbulence warnings from other aircraft and that they were clear of all weather.