What happened
On June 15, 2023, at approximately 13:30 JST, an Aerospatiale AS332L1 helicopter, registration JA9678, was conducting external cargo sling operations in Nantan City, Kyoto Prefecture. The mission involved transporting materials for power line replacement work from a loading site to an unloading site.
The aircraft was lifting three cargo nets simultaneously. As the helicopter began its climb, one of the nets (Cargo net 1) became snagged on a rootstock. In an attempt to clear the obstruction, a ground operator moved toward the load to perform support work. While the operator was engaged in this task, a second cargo net (Cargo net 2) began to swing in a counter-clockwise direction as the tension on the sling wires increased. This swinging net struck the ground operator's arm, resulting in serious injury characterized by extensive skin exfoliation.
The investigation
The JTSB investigation examined the roles and communications of the flight crew and ground personnel. The investigation focused on the movement of the ground operators, the monitoring duties of the onboard mechanic, and the signaling procedures between the ground team and the cockpit. The investigators also reviewed the company's safety regulations regarding ground operations and the specific sequence of events leading to the contact between the cargo and the personnel.
Findings
- The ground operator failed to move to a designated safe position after hooking the cargo, choosing instead to perform manual support work to clear a snagged net.
- The ground operator did not notify the onboard mechanic or the signaling ground operator of their intention to approach the cargo.
- The signaling ground operator did not notice the movement of the first operator toward the load.
- The onboard mechanic observed the ground operator performing support work but continued to guide the helicopter's climb, assuming there was no danger because no specific signal was received from the signaling operator.
- Inadequate communication between the ground operators and the onboard mechanic contributed to the failure to halt the ascent.