What happened
On October 10, 2016, a Rolladen-Schneider LS4-b glider, registered JA22WP, was participating in a gliding competition at the Menuma Gliding Field in Saitame Prefecture. The aircraft, owned by Waseda University, was winch-launched as part of a competition sponsored by the Japan Students Aviation League.
During the flight, the pilot attempted to follow the airfield traffic pattern to maintain a competitive position. While flying at a low altitude of approximately 220 meters, the pilot initiated a steep right turn to enter the downwind leg, intending to land near two other gliders that had already departed. During this maneuver, the aircraft's ground speed was approximately 70km/h, which was near its stall speed. The aircraft entered a nosedive, and although the pilot attempted a recovery, the glider stalled a second time. This led to a left spin that lasted for approximately 2.5 rotations, ending in a crash in Oizumi Town, Gunma Prefecture. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
The Japan Transport Safety Board (JTSB) examined the aircraft's flight records, GPS data, and communications. Investigators analyzed the aircraft's weight and balance, specifically the center of gravity (CG) position. It was noted that the pilot had removed one of the usual trim weights for the competition, placing the CG at approximately 4.5% forward from the aft limit.
The investigation also reviewed the pilot's recent flight history and transition from a different aircraft type, the Alexander Schleicher ASK23b. Investigators looked into the club's training syllabus, coaching methods, and the specific flight characteristics of the Rolladen-Schneider LS4-b, which is a high-performance glider requiring precise control.
Findings
- The aircraft was flying with a center of gravity position near the aft limit, which significantly reduces stability and makes the aircraft more susceptible to stalls and spins.
- The pilot had not yet fully mastered the specific handling characteristics of the Rolladen-Schneider LS4-b, particularly regarding speed control, after transitioning from a different glider model.
- The aircraft entered a stall due to a steep bank angle and low airspeed during the landing approach.
- The pilot's attempt to recover from the initial stall at a low altitude resulted in a secondary stall and an unrecoverable left spin.