What happened
On July 19, 2020, at approximately 13:00, a privately owned Cessna 172N RAM, registered JA3825, crashed into a mountain slope in Minamifurano-cho, Hokkaido. The aircraft was performing flight training maneuvers, specifically slow flight, between Ikutora and Ochiai. During the flight, the crew transitioned positions, with the captain moving from the right seat to the left seat to take control while the trainee moved to the rear seat.
While navigating the mountainous terrain, the aircraft approached a mountain peak located east of the flight path. The captain attempted to execute a left turn to avoid the terrain while applying full engine power. However, the aircraft experienced a rapid descent, which the captain attributed to encountering a downdraft. During the maneuver, the aircraft likely entered a spin, leading to a collision with the mountain slope. The impact left the aircraft upside down in a wooded area, and both the captain and the trainee sustained serious injuries.
The investigation
The Japan Transport Safety Board (JTSB) examined the wreckage, the flight path, and meteorological data from nearby stations. Investigators analyzed the damage to the airframe, noting that the spinner, fuselage, and wing components had sustained significant impact damage from trees. The investigation also reviewed the flight instruments and the specific survey map being used by the crew, which indicated a flight altitude of 2,600 ft, despite the crew's recollection of 3,000 ft.
Meteorological analysis from the Obihiro wind profiler and regional stations suggested relatively stable wind conditions with no significant large-scale downdrafts in the area. The investigation also noted that the aircraft was not equipped with any flight data recorders, making it difficult to reconstruct the precise flight conditions leading up to the impact. Additionally, while an Emergency Locator Transmitter (ELT) was onboard, it was stored in a box and could not be quickly located by the crew following the crash.
Findings
- The aircraft was operating at a low altitude relative to the terrain, providing insufficient altitude above ground level (AGL) for safe maneuvering in mountainous areas.
- The crew demonstrated a lack of awareness of safe flight by conducting training in terrain that closely matched their flight altitude.
- The transition of the pilot in command from the right seat to the left seat during the flight was a dangerous maneuver.
- The use of a non-standard survey map, which differed from the actual flight altitude, may have contributed to the loss of situational awareness.
- The lack of flight data monitoring equipment prevented a detailed reconstruction of the aircraft's performance immediately prior to the accident.