Accident Overview
On July 19, 2020, at about 13:00 Japan Standard Time, a privately owned Cessna 172N RAM (registration JA3825) crashed into a mountain slope in Minamifurano-cho, Sorachi-gun, Hokkaido. The aircraft was being used for flight training, with a captain acting as flight instructor and a trainee. Both occupants sustained serious injuries. The aircraft was destroyed, but no fire occurred. The accident site was located at approximately latitude 43° 07' 13" north and longitude 142° 42' 38" east, on a wooded slope with about 30 degrees of incline. After the crash, the aircraft came to rest inverted, with its nose facing upslope and the tail supported by trees.
Flight History
The aircraft departed from Sapporo Airfield at about 10:51 under visual flight rules. Onboard were the captain (right seat, instructor) and the trainee (left seat, pilot flying). The pre-flight inspection revealed no anomalies, and the fuel quantity was about 52 gallons (approximately 6 hours 30 minutes of endurance). The flight proceeded via waypoint KURIS toward Kanayama Dam at an altitude of about 5,500 feet over the Yubari Mountains, then descended to about 4,000 feet. After reaching Kanayama Dam, the aircraft performed slow flight over Lake Kanayama, then conducted straight-and-level slow-flight training between Ikutora (Point A) and Ochiai (Point B) in Minamifurano-cho. The altitude was initially about 4,000 feet but was later changed to about 3,000 feet. The trainee was at the controls until midway through the shuttle flights; then, for two round trips before the crash, the trainee moved to the rear seat to observe instruments and take photos, while the captain moved to the left seat to operate the aircraft. During this phase, flaps were set at 10° and airspeed was approximately 60 knots. The crew used a survey map rather than standard aeronautical charts.
Immediately before the accident, the aircraft was flying at 3,000 feet from Ikutora toward Ochiai. It approached a mountain east of Ochiai at the same altitude, but the captain was delayed in noticing it. While encountering turbulence, including downdrafts, the aircraft attempted to turn back; however, mountain peaks of equal height were present on both sides, so a left turn was initiated. The captain stated that after beginning the turn, engine power was set to maximum, but altitude decreased rapidly due to downdrafts, making a collision with the mountain unavoidable. The captain attempted to place the aircraft in a near-stall condition to maneuver between trees, setting the airspeed similar to that just before touchdown in a normal landing. The engine remained at full power. The aircraft then impacted the slope. After the crash, the captain evacuated but returned to turn off all switches due to fire concerns.
Injuries and Damage
Both the captain and the trainee suffered serious injuries. The aircraft was destroyed. Specific damage included: the spinner crushed and deformed; skin torn off between the engine mounting area and cabin; left main wing strut fractured at its attachment point with tree chips attached; aft fuselage cargo compartment buckled. The left main wing was damaged between flap and aileron, and its tip was torn off. The horizontal stabilizer struck trees, and the elevator was asymmetrical; the rudder skin showed slight damage. After the crash, examination of the aircraft control system revealed: master switch OFF, mixture RICH, throttle pushed in about two-thirds forward, both fuel selectors ON, flap lever at 10°, and altimeter set to 29.88 inHg. The engine showed no external damage or oil leaks, cylinder compression was normal, ignition and lubrication systems operated normally, and no foreign material was found in the carburetor filter. One of the two propeller blades was bent backward. The Emergency Locator Transmitter (ELT) was a manually operated type stored in the cargo compartment and was not activated.
Personnel Information
The captain, age 66, held a Commercial Pilot Certificate (since December 1972), Flight Instructor Certificate (since January 1991), and Instrument Flight Certificate (since June 1994). His Class 1 medical certificate was valid until April 2021. Total flight time was 13,702 hours 9 minutes, with 11,407 hours 56 minutes on the accident aircraft type. The trainee, age 52, held a Flight Training Certificate valid from August 30, 2019, to August 29, 2020. Total flight time was 473 hours 5 minutes, with 468 hours 30 minutes on type.
Aircraft Information
The aircraft was a Cessna 172N RAM, serial number 17271480, manufactured May 30, 1978. It had no standard Certificate of Airworthiness but was operated under an approval (No. 2020-0016) valid from May 25 to August 24, 2020, in the Normal, Utility, or Special category. Total flight time at the time of the accident was 9,979 hours 48 minutes. Weight and center of gravity were within allowable limits. The engine was a Lycoming O-320-D2G, serial number L-10422-32E, manufactured July 21, 2010, with 1,144 hours 15 minutes total time. The aircraft was not equipped with any flight data recorders or surveying instruments.
Meteorological Conditions
A weather outlook issued by the New Chitose Aviation Weather Station at 05:00 on the day of the accident indicated a pressure trough over the Hokkaido region through July 19, bringing rain to some areas on the Pacific side. Low cloud cover was expected due to humid air and temperature drops, with fog or mist in some places. Local observation data from Ikutora and Shintok were available but are not detailed in the report.