What happened
On January 7, 2023, a Japan Airlines Boeing 737-800, registration JA307J, was operating a scheduled flight from Tokyo International Airport to Miyazaki Airport. During the approach phase, the pilot in command noted reports of other aircraft encountering turbulence in the area. In a precautionary measure, the pilot activated the seat belt sign before the aircraft reached the cloud layer.
As the aircraft descended through a layer of cumulus clouds at approximately 11,000 feet, it encountered sudden and intense shaking. Flight data from the Quick Access Recorder (QAR) indicated that the aircraft's heading shifted 4 degrees to the left, accompanied by fluctuating lateral acceleration. During this period of instability, a passenger seated in the rear of the cabin was thrown against the seat armrest. While the passenger did not report pain immediately upon landing, subsequent medical examination revealed fractures to the left eighth and ninth ribs.
The investigation
The Japan Transport Safety Board (JTSB) examined meteorological data, aircraft flight records, and the physical mechanics of the impact. Investigators analyzed the aircraft's movement using QAR data, which showed a momentary yawing motion and lateral acceleration changes. The investigation also focused on the passenger's position, noting that the individual was seated in seat 39H, approximately 12 meters from the aircraft's center of gravity.
Findings
Investigators determined that the turbulence was caused by convective activity within the cumulus clouds the aircraft was skimming. The investigation established that the aircraft experienced a significant yawing motion, causing the tail section to rotate. Due to the laws of inertia, while the aircraft's body moved laterally, the passenger's upper body swung to the left. This motion caused the passenger's left side to strike the metallic and plastic armrest with enough force to cause the bone fractures.
Safety action
Following the incident, Japan Airlines shared the details of the accident with all employees and integrated the case into departmental safety meetings. The airline has focused on disseminating safety protocols to prevent similar injuries resulting from aircraft shaking.