What happened
On August 21, 2012, an Asiana Airlines Airbus A330-300, registered HL8258, was operating a scheduled flight from Honolulu to Incheon. While cruising at approximately 40,000 feet over Matsue City, Japan, the aircraft encountered sudden and violent atmospheric disturbances.
Data from the flight recorders indicates that the aircraft experienced rapid changes in wind direction and speed, accompanied by strong updrafts. During the event, the aircraft's speed exceeded its maximum operating limit, triggering an overspeed warning. The pilot in command disengaged the autopilot to manually stabilize the aircraft, during which time the plane underwent significant vertical and lateral oscillations.
As a result of the intense shaking, one passenger walking in the rear aisle sustained serious injuries. A second passenger, who had unfastened their seatbelt to assist the injured individual, also suffered serious injuries when a second bout of severe shaking occurred. One additional passenger sustained minor injuries. The aircraft itself sustained no structural damage.
The investigation
The Japan Transport Safety Board (JTSB) examined flight data from the Digital Flight Data Recorder (DFDR) and Cockpit Voice Recorder (CVR), alongside air traffic control communications and interviews with crew and passengers. The investigation focused on the meteorological conditions, the flight crew's response to the turbulence, and the operational status of the aircraft's onboard systems.
Findings
- The primary cause of the passenger injuries was the severe shaking of the aircraft while passengers were unseated or attempting to assist others.
- The initial turbulence was likely caused by the aircraft passing through or near cumulonimbus clouds, characterized by intense wind shear and vertical acceleration.
- The flight crew failed to notice that the weather radar was turned off, which prevented them from detecting the convective activity ahead.
- Monitoring of weather conditions and cockpit instruments by the pilots was insufficient.
- The pilot's use of non-standard terminology—reporting "Big Turbulence" instead of "Severe Turbulence"—to Tokyo Air Traffic Control may have hindered the timely dissemination of safety information to following aircraft.