What happened
On July 2, 2025, an Aerospatiale AS332L1 helicopter, registration JA6686, was performing an underslung cargo transport mission in Hamamatsu City, Shizuoka Prefecture. The aircraft was moving approximately 800 kg of steel pipes from a loading site near a steel tower to an operational site. During the flight, while traveling at an airspeed of roughly 40 knots at an altitude of 500 feet, the captain observed through the cargo mirror that part of the lashing material was trailing and falling from the load.
Upon notification, a crew member inspected the cargo from the cabin door and confirmed that one end of the lashing material—which included a ton bag, netting, and binding wire—had detached. The remaining end of the lashing was flapping violently in the wind and appeared at risk of further detachment. To mitigate the risk, the pilot reduced the aircraft's speed to a near-hover state before landing at the destination. Post-flight inspection revealed that approximately 4 kg of lashing materials had been lost during the flight. There were no injuries to the three crew members on board.
The investigation
The JTSB investigation focused on the integrity of the cargo packaging and the adherence to safety protocols. Investigators examined the packing methods used by the ground crew, specifically looking at the use of "ton packs" (large flexible containers) to secure the ends of the steel pipes. The investigation also reviewed the safety education provided to the workers involved in the loading process and the oversight provided by the prime contractor.
Findings
Investigation findings revealed that the cargo was not secured according to the established safety text. Specifically, the procedure to tie the ton packs together at both ends to prevent wind-induced movement was omitted, reportedly because there was an insufficient supply of rope at the time of packing. Furthermore, the required "Adamaki" winding method, intended to further secure the ends, was not utilized. Instead, the binding wire was wound directly around the pipes.
It was determined that the wind pressure acting on the bag-shaped ton packs during forward flight caused the lashing material to detach. Additionally, the investigation found that some ground workers involved in the operation had not received the required safety education. While the pilot's decision to slow the aircraft was an appropriate response to prevent further loss, the fundamental failure lay in the improper securing of the load.
Safety action
Following the incident, the operator implemented several changes, including a general prohibition on using ton packs for such loads in principle, favoring soft sling methods instead. The company also established new safety education regulations and created a manual for instructors. To ensure compliance, the company now requires sales representatives to verify packing conditions via photographs before operations begin, and flight mechanics have been instructed to refuse any load that does not meet safety standards.