Accident Summary
On Friday, March 6, 2015, at approximately 10:51 Japan Standard Time, an Aerospatiale AS332L1 helicopter, registered JA6741, operated by Shin Nihon Helicopter Co., Ltd., crashed after colliding with power transmission lines. The helicopter was engaged in external load transportation and had just departed from a hover at a forward base loading site in Kii-Nagashima temporary helipad area. The aircraft struck the wires, resulting in destruction and a post-impact fire.
Flight History
The helicopter had taken off from Nagoya Airfield earlier that morning at 08:09 with the captain (right seat) and an on-board mechanic (monitor seat). After a preliminary survey flight to confirm sling length and obstacle locations, it landed at the helipad at 08:58. Following a task briefing, it departed again at 10:05 for load transport operations between a forward base and a valley site. During the second sortie, after depositing steel frames at the forward base, the helicopter began climbing from a hover at an altitude of about 12–13 m. Witnesses reported hearing an explosive sound as the helicopter struck the power lines. The tail boom separated, main rotor blades broke, and the fuselage fell to the ground engulfed in flames.
Injuries and Damage
Both crew members—the captain, aged 53, and the on-board mechanic—were fatally injured. The helicopter was destroyed by impact and fire. The tail boom, main rotor blades, and tail rotor blades were broken or ruptured; the engines and fuselage were burned. Two power transmission lines were cut, causing a four-minute power outage affecting approximately 18,700 households.
Probable Cause
The Japan Transport Safety Board determined that it is highly probable the helicopter did not maintain sufficient separation from the power transmission lines during its climb from the hover, leading to the collision. It is somewhat likely that the captain either did not visually acquire the wires in time or misjudged the distance to them.