MIHAMA, Fukui -- The government is investigating how a helicopter dropped an 800-kilogram wooden box on a mountain in this town hosting Kansai Electric Power Co.'s Mihama Nuclear Power Plant on March 1.
No injuries were reported.
The chopper, operated by Tokyo-based Aero Asahi Corp., was flying at an altitude of about 100 meters in a mountainous area of Mihama, Fukui Prefecture, at around 10:08 a.m. The wooden box was holding power line pylon insulators bound for a construction site. The pylons support power cables running from the Mihama plant to an electrical substation.
The Ministry of Land, Infrastructure, Transport and Tourism determined that the case constituted a "serious incident," prompting the ministry's Japan Transport Safety Board to dispatch two aircraft accident investigators to the site later that day.
According to Kansai Electric, which placed the shipment order, the helicopter took off from a heliport in Mihama and was en route to the construction site about 2.1 kilometers away. However, the aircraft dropped the box along with the net holding it after traveling about 700 meters. It emerged that one end of a wire rope that was holding the netted box had come free of one of the hooks on the bottom of the chopper.