What happened
On June 12, 2011, a Sportavia SF25C motor glider, registered JA2168, was performing a familiarization flight at the Shinshinotsu gliding field in Hokkaido, Japan. The flight, operated by a private pilot, was nearing its conclusion when the aircraft encountered unexpected aerodynamic conditions during its final approach.
While flying the final leg of the approach, the pilot noted the aircraft was drifting rightward and experiencing turbulence. At an altitude of approximately 100 feet, the aircraft began to deviate upward from the intended glide path. In an attempt to correct this upward drift, the pilot applied significant force to the spoiler lever, moving the spoilers from a half-extended to a fully extended position. This rapid deployment caused the aircraft's nose to pitch down sharply and significantly increased the rate of descent.
Despite the pilot's immediate attempt to retract the spoilers and pull the control stick to flare the aircraft, the low altitude left insufficient time to recover the nose-up attitude. The aircraft struck the runway with a violent, nose-down impact. The impact caused the main wheel to detach and the propeller blades to break, leading the aircraft to slide approximately 30 meters along the runway.
The investigation
The Japan Transport Safety Board (JTSB) examined the aircraft's flight path, the wreckage, and meteorological data from the time of the accident. Investigators analyzed the damage to the Sportavia SF25C, which included a broken propeller, deformed engine components, and structural cracks in the wings.
Meteorological evidence indicated that while winds at the flight service station were light, winds over the nearby river bank were significantly stronger, reaching up to 13 knots. This discrepancy suggested the presence of updrafts and downdrafts caused by the terrain. The investigation also reviewed the pilot's control inputs and the mechanical response of the spoilers during the critical moments of the approach.