Accident Overview
On Sunday, September 26, 2010, at about 07:50 local time, an Aerospatiale AS332L helicopter, registered JA9635 and operated by Aero Asahi Corporation, crashed into a mountain slope near the Kigensugi cedar tree in Yakushima-Town, Kumage-Gun, Kagoshima Prefecture. The helicopter was engaged in sling load cargo transport of construction materials for mountain trail maintenance, shuttling between Yakusugi Land temporary helipad and unloading sites near Yodogawa Mountain Hut.
Flight History
The helicopter had performed five previous airlifts that morning. During the sixth cargo lift, the helicopter took off with underslung cargo. Witnesses reported hearing the helicopter approach, then sounds of the aircraft turning away due to worsening weather. A person near the Kigensugi cedar tree observed the helicopter flying in a valley toward the hut, then heard loud rustling sounds like something hitting trees, followed by dry whirring sounds and then big pealing noises. He hid behind a tree and later saw smoke rising from the mountain ridge.
Wreckage and Injuries
Both the pilot and the loadmaster on board suffered fatal injuries. The helicopter was destroyed and consumed by fire. Trees in the national forest area were damaged, including fire damage.
Probable Cause
The Japan Transport Safety Board determined that the accident likely occurred when the helicopter, while flying in a mountain valley with underslung external cargo, made a left turn to turn back. During this maneuver, the helicopter neared the slope and its underslung cargo became caught in ground objects, leading to the crash. Subsequent fire consumed the helicopter.
The report noted several possible contributing circumstances: capable out-of-ground-effect hovering for turn-around was not performed; en route altitude was well below the minimum safe altitude; climbing was restricted during the left turn due to a low cloud base; and the crew failed to properly judge cargo clearance from ground objects.