Investigation Summary
The accident occurred during a short domestic hop from Sapporo to Hakodate. As the aircraft approached its destination, it encountered significant meteorological challenges, including low cloud cover and strong southwesterly crosswinds. These winds caused the aircraft to drift further north than the crew realized. The pilots were attempting a standard arrival procedure that required crossing the Hakodate non-directional beacon (NDB) at 2,500 feet. However, due to the wind drift and lack of radar monitoring, the crew mistook their position and began a circling descent from 6,000 feet prematurely. The outbound leg of their maneuver extended too far west and north, placing the aircraft directly in the path of Yokotsudake. The aircraft was descending through 1,800 meters (approximately 5,900 feet) during this premature approach phase when it struck the southern face of the mountain, which has a peak elevation of approximately 1,167 meters (3,829 feet), resulting in the total disintegration of the airframe.
Final Conclusions
The Japan Aircraft Accident Investigation Commission (AAIC) concluded the cause was controlled flight into terrain (CFIT) resulting from pilot error. The crew failed to accurately determine their position relative to the Hakodate NDB due to strong winds and atmospheric turbulence. Their premature descent, conducted without positive identification of their location, led the aircraft into the side of a mountain while operating in Instrument Meteorological Conditions (IMC).
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Non-Directional Beacon (NDB)
A ground-based radio transmitter used for navigation; the crew misidentified their passage over the Hakodate NDB.
Instrument Meteorological Conditions (IMC)
Weather conditions that require pilots to fly primarily by reference to instruments; the crew was flying blindly through clouds at the time of impact.
Interesting Facts
- 01The aircraft was named 'Bandai-go'.
- 02At the time, it was the deadliest accident involving the NAMC YS-11.
- 03The crash site was located approximately 11 miles north of Hakodate Airport.
- 04Strong southwesterly winds caused the aircraft to drift significantly off its intended course.
- 05The impact occurred on the steep southern face of the mountain while the aircraft was in thick clouds.
Safety Actions & Advisories
Radar Coverage Expansion
The accident spurred improvements in regional radar coverage to better track domestic flights in mountainous areas.
Approach Protocol Revision
Stricter approach protocols were implemented across Japan's domestic network to prevent premature descents without positive position fixes.