What happened
On 6 May 2016, a Hong Kong Airlines Airbus A330-223, registration B-LNE, was operating a scheduled passenger flight from Bali, Indonesia, to Hong Kong. During the flight, the crew observed lightning near their path and elected to climb to Flight Level 410 to avoid deteriorating weather. While navigating between two large cloud cells, the aircraft encountered light turbulence, and the weather radar began displaying magenta-colored areas approximately 5 nautical miles ahead.
At 18:34 UTC, the aircraft entered a zone of severe turbulence that lasted for approximately one minute. The sudden, intense vertical movement caused the autopilot to disengage due to a significant Angle of Attack excursion. In the aft galley, the turbulence was violent enough to lift food carts and strike the ceiling. The incident resulted in 15 injuries, involving 3 flight attendants and 12 passengers. The aircraft subsequently returned to Bali, where medical assistance was waiting for the injured occupants.
The investigation
The KNKT investigation focused on the meteorological conditions, the aircraft's radar performance, and the crew's response. Investigators analyzed flight data recorder (FDR) and cockpit voice recorder (CVR) information, noting that the aircraft was flying within identified cumulonimbus clouds during the encounter. The investigation also examined the physical damage to the passenger service units and the aft galley ceiling, as well as the cabin crew's ability to warn passengers during the sudden onset of turbulence.
Findings
- The weather radar likely over-scanned the storm cell due to the selected tilt angle, which caused the pilots to underestimate the intensity of the turbulence associated with the approaching weather.
- Because there was no specific warning of the impending severe turbulence, flight attendants had not yet secured the galley carts or seated themselves with seatbelts fastened.
- The severity of the injuries to passengers was increased because several seatbelts were not properly fastened, despite the crew having previously instructed passengers to remain buckled.