Flight Details
On Tuesday, August 21, 2012, an Airbus A330-300, registered HL8258, operated by Asiana Airlines Inc., departed from Honolulu International Airport for Incheon International Airport as scheduled flight 231. The aircraft carried 221 people: a pilot in command (PIC), 14 other crew members, and 206 passengers. At the time of the incident, the PIC was in the left seat as pilot monitoring, and the Route Captain (R Captain) was in the right seat as pilot flying.
Sequence of Events
According to the Digital Flight Data Recorder (DFDR) and Cockpit Voice Recorder (CVR), the aircraft was cruising at FL400 under autopilot. At approximately 15:16:14 JST, a small change in vertical acceleration began. At 15:16:24, the FCU speed selector was set to M0.78. Around 15:16:30, the wind, previously from the right rear at 16 kt, began to shift counter-clockwise. Shortly after, the aircraft encountered significant atmospheric disturbances.
At 15:16:38, the wind speed reached 34 kt, and the aircraft's speed temporarily exceeded M0.86 (MMO), triggering an overspeed warning. The altitude increased. At 15:16:40, the static air temperature rose rapidly by 4°C, and vertical acceleration peaked at 1.88G. The wind then became a crosswind from the left, with vertical acceleration dropping to 0.04G at 15:16:42—the greatest change during the flight.
Cabin attendants made a passenger address regarding shaking and seat belt fastening from 15:16:44 to 15:17:07. At 15:16:48, the PIC disengaged the autopilot. The sidestick was pushed forward at 15:16:54, causing a rapid pitch change to -6.3° and vertical acceleration of -0.09G. The wind became a tailwind and increased to 52 kt at 15:16:55. The roll angle varied between 30.2° right and 17.9° left, and pitch angle reached +14.8°.
Injuries and Damage
Two passengers sustained serious injuries, and one passenger sustained slight injuries. The aircraft was not damaged.
Probable Cause
It is highly probable that in this accident, serious injury was sustained by a passenger walking in the rear aisle due to the severe shaking of the Aircraft, and that serious injury was sustained by another passenger seated nearby when the passenger removed the seat belt in order to help the injured passenger, the Aircraft shook severely again at that moment. It is probable that the initial severe shaking of the Aircraft was a result of the Aircraft passing through or nearby cumulonimbus, due to the PIC and the R Captain failing to notice that the weather radar was off, and encountering atmospheric disturbances with severe changes in wind direction and speed coupled with strong updrafts. It is possible that the next shaking of the Aircraft may have been influenced by the PIC’s control operations after disengaging the A/P to stabilize the aircraft. It is probable that the reason for the PIC and the R Captain failing to notice that the weather radar was off was that their monitoring of the weather conditions and instruments was insufficient.