What happened
On October 3, 2022, a Boeing 737-800, registration JA07RK, operated by Japan Transocean Air Co., Ltd., was performing a scheduled flight from Naha Airport to Komostu Airport. While cruising at 41,000 feet, the aircraft encountered an initial period of significant shaking. In response, the pilot in command initiated a descent to 39,000 feet, and subsequently to 37,000 feet, to mitigate the turbulence.
At approximately 12:54 JST, once the aircraft reached a stable condition at 37,000 feet, the pilot turned off the seat belt sign to allow passengers to use the lavatories. As a cabin crew member moved into the aisle to attend to passengers, the aircraft encountered a second, intense period of lateral shaking. The force of the movement caused the crew member to strike the left side of the aisle wall. To prevent being thrown toward the right side of the cabin, the crew member braced by grabbing a passenger seat headrest and stepping firmly with their right foot. This sudden impact resulted in a right pollex pedis sesamoid fracture.
The investigation
The Japan Transport Safety Board (JTSB) examined flight records from the Quick Access Recorder (QAR) and interviewed the crew. The investigation focused on the meteorological conditions and the physical mechanics of the injury. Analysis of the QAR data revealed that during the second shaking event, wind velocity fluctuated significantly, dropping from 56 knots to 46 knots before increasing back to 65 knots. This coincided with changes in the aircraft's bank angle and heading.
Investigators also reviewed weather forecasts and radar data. Prior to the flight, no significant weather phenomena or turbulence were forecasted along the route, and the aircraft was flying in clear air without visible clouds. Furthermore, no other aircraft had reported turbulence in the vicinity, and the onboard weather radar showed no signs of impending instability.
Findings
- The injury was caused by a heavy load placed on the sole of the crew member's right foot, resulting from the combination of vertical and lateral acceleration during the sudden movement.
- The lateral shaking was particularly pronounced in the aft section of the cabin due to the aircraft's yaw movements.
- The fluctuation in wind velocity was the primary driver of the unexpected shaking.
- The crew member's ability to avoid a more serious fall was attributed to effective company training regarding how to brace during unexpected turbulence.
Safety action
Following the incident, the operator reinforced its injury prevention campaigns, issuing safety alerts to all cabin crew members. The company also updated its training protocols to ensure all crew members receive practical instruction on body positioning and bracing techniques during initial and regular training sessions.