What happened
On March 5, 2017, a Bell 412EP helicopter, registered JA97NA, departed from Matsumoto Airport as part of a rescue training mission. Operated by the Nagano Fire and Disaster Prevention Aviation Center, the aircraft was en route to a temporary mountain helipad in Shiojiri City. During the flight, the helicopter struck trees and crashed onto a slope on Mt. Hachibuse in Matsumoto City. The accident resulted in nine fatalities, as all nine individuals on board—including the captain, a mechanic, and seven rescuers—lost their lives. While the aircraft was destroyed upon impact, no fire broke out at the crash site.
The investigation
The Japan Transport Safety Board (JTSB) conducted an extensive investigation, utilizing drone imagery and examining the aircraft's autopilot computer. Investigators scrutinized the flight's history, the crew's medical backgrounds, and the operational procedures in place at the time. The probe also looked into the functionality of the aircraft's Emergency Locator Transmitter (ELT), which failed to activate following the impact, and examined the captain's use of a camera during low-altitude flight.
Findings
Investigators determined that the primary cause of the crash was the failure to execute an avoidance maneuver while the helicopter was approaching the terrain. It was noted that the captain's reduced level of arousal may have prevented him from recognizing the imminent danger, though this could not be definitively proven.
Crucially, the investigation revealed that the captain had a significant medical and surgical history for which he was receiving medication, yet he had failed to disclose this information when applying for his aviation medical certificate. Additionally, the captain was observed using a camera during the low-altitude flight, which likely compromised his ability to maintain a proper lookout. The investigation also noted that the ELT's G-switches may have been stuck, preventing activation, highlighting a need for more rigorous maintenance inspections.