Accident Details
On October 12, 2021, at approximately 09:39 JST, a privately owned Schempp-Hirth Arcus M motor glider, registration JA11AM, crashed while turning after departing from the Biei Glider Field in Biei Town, Kamikawa County, Hokkaido Prefecture. The glider had taken off from the southeast end of the field toward the northwest using self-launching capability for a leisure flight. As it climbed and began a left turn, the engine sound suddenly stopped when the turn reached about 90 degrees. The glider continued the left turn without descending, then entered a left spin at approximately 100 meters above ground level and nosedived. After one turn, the spin stopped and the nose began to rise slightly before the glider crashed into the Biei River. The witness, a fellow pilot who had assisted with pre-flight preparations, saw the crash and found both pilots unconscious. The fire brigade transported them to a hospital, where they were pronounced dead.
Aircraft and Crew Information
The glider was a two-seat Schempp-Hirth Arcus M, serial number 229, manufactured on January 25, 2021. It had a total flight time of 15 hours 25 minutes at the time of the accident. The engine was a Solo type 2625-02i two-stroke engine, serial number 479/288, manufactured on September 20, 2020, with 2 hours 44 minutes of total time in service. The glider's weight was estimated at approximately 750 kg, within the maximum takeoff weight of 850 kg, and the center of gravity was within the allowable range.
Pilot A, aged 69, held a private pilot certificate for gliders since 1974, with a motor glider type rating and a class 2 aviation medical certificate. Total flight time was 3,320 hours 54 minutes, including 465 hours 35 minutes on the type. Pilot B, aged 68, held a private pilot certificate for gliders (without tow hook) since 2014, with a class 2 medical certificate. Total flight time was 3,758 hours 18 minutes, including 390 hours 55 minutes on the type. Both pilots sustained fatal injuries: Pilot A had cerebral contusion and a fracture of the lower right tibia; Pilot B had cerebral contusion.
Investigation Findings
The glider was destroyed, but no fire occurred. Examination of the wreckage revealed a broken fuselage, wing damage, and a collapsed power plant. The control system had no failures. The engine showed no abnormal combustion or internal destruction, but continuity checks on the airframe side of the ignition system revealed a disconnection. The propeller blades had dents on the rear surface. The flap levers in both seats were found in the "+2" position, which is used for climb after takeoff; however, the glider had been moved from the crash site before the initial investigation, so the positions at the time of the crash were not directly confirmed.
A dashcam in a nearby vehicle recorded about four seconds before impact, showing the glider spinning into a nosedive. A security camera recorded engine sound and an impact sound about 10 seconds after the engine stopped. GPS data showed the glider accelerated to the climb speed of 51 knots indicated airspeed and maintained it until the record stopped 41 seconds after takeoff. The average bank angle during the left turn was about 24 degrees. The altitude at the start of the left turn (29 seconds after takeoff) was 76 meters, reaching 107 meters before the record stopped.
Weather conditions at Biei Regional Meteorological Observatory, about 7 km northwest, indicated west wind at 1.3 m/s and 13.0°C at 09:40. The witness reported clear skies and calm conditions.