What happened
On April 26, 2015, a Scheibe SF34B glider, registration JA2446, was conducting a specialized flight training session at the Nirasaki Gliding Field in Yamanashi Prefecture, Japan. The flight, operated by the Nirasaki-city Aviation Association, involved an instructor and a trainee performing a maneuver designed to simulate an off-field landing. This required the aircraft to approach the runway at a specific angle and altitude.
During the approach, the aircraft was flying at an altitude lower than its standard training profile. As the glider transitioned toward the left base of the runway, it encountered downdraft conditions. The aircraft's altitude dropped significantly, and the crew attempted to turn toward the runway earlier than planned to compensate for the low height. During this turn, the left wingtip made contact with the ground in front of the runway. The subsequent hard landing caused the aircraft to bounce, skid sideways across the runway, and eventually come to a stop at the western edge of the field.
The investigation
Investigators from the JTSB examined the flight history, meteorological conditions, and the physical state of the aircraft. The investigation focused on the decision-making process of both the instructor and the trainee, as well as the impact of local air currents. The inspection of JA2446 revealed substantial damage, including a broken left wingtip, cracks in the wing, a distorted fuselage, and a tail wheel that had been forced into the fuselage structure.
Findings
- The instructor had intentionally set a lower approach altitude for the training exercise but failed to verify the actual altitude using the altimeter during the maneuver.
- The trainee, while experiencing difficulty judging the altitude during this new training subject, did not communicate these concerns to the instructor.
- The instructor did not provide timely corrective advice or intervention despite noticing the altitude was lower than usual.
- The training was continued despite the aircraft being at an altitude below what was necessary to safely complete the maneuver.
- Local downdrafts likely contributed to the unexpected loss of altitude during the approach.