What happened
An Air Wisconsin aircraft operating as United Express Flight 684 was executing the Thompson One Arrival procedure into Denver. The flight crew had received clearance to descend from flight level 190 down to an altitude of 13,000 feet. During this descent phase, the airplane passed through 14,000 feet when it unexpectedly encountered clear air turbulence that was neither reported by other aircraft nor anticipated by the crew.
The sudden and unanticipated nature of the turbulence caused significant disruption within the cabin. At the time of the incident, two flight attendants were performing their standard pre-landing safety checks. The violent motion associated with the turbulence resulted in serious injuries to both crew members involved in the cabin inspection.
Findings
The investigation into the incident focused on the mechanical integrity of the aircraft and the circumstances surrounding the turbulence encounter. Key findings included:
- Clear air turbulence: The primary factor was the encounter with unreported clear air turbulence at 14,000 feet during descent.
- Injury severity: One flight attendant suffered fractures to her pelvis, collarbone, and two ribs. The second flight attendant sustained a fractured ankle.
- Operational context: The injuries occurred while crew members were conducting routine pre-landing cabin checks, highlighting the risks associated with turbulence in unsecured or partially secured areas.