What happened
On August 19, 2000, a student pilot was conducting training maneuvers at the Ambri aerodrome in Switzerland. While performing a winch launch in a Schleicher Ka8B, registration HB-908, the winch cable snapped at an altitude of approximately 90 to 100 meters.
Following the cable break, the pilot initially maintained control and executed a right-hand turn to return to the runway. However, while attempting a second turn at an altitude of roughly 50 to 60 meters, the pilot increased the bank angle to approximately 60 degrees in an attempt to realign with the runway axis. Due to the high bank angle and significantly reduced airspeed, the glider entered a steep descent, striking the ground with the right wingtip and flipping over. The pilot sustained fatal injuries.
The investigation
SUST examined the condition of the winch equipment and the flight maneuvers performed. The investigation focused on the mechanical integrity of the towing cable and the decision-making process of the pilot during the emergency. Technical analysis of the cable revealed that it was in poor condition, featuring ten separate repairs using press sleeves and ten points of significant wire breakage. Laboratory testing by EMPA determined that the cable's breaking strength was approximately 37% below the minimum requirement for a new cable.
Furthermore, the investigation found that the winch operator had not inspected the cable prior to the day's flight operations. The investigation also reviewed the student pilot's training records and the flight tactics employed immediately following the cable separation.
Findings
- The primary cause of the crash was the loss of control during a low-altitude turn following the winch cable failure.
- The winch cable was in poor condition, with significant wear and multiple previous repairs.
- The pilot employed inadequate flight tactics by attempting a second steep turn at low altitude rather than opting for a straight-ahead landing or utilizing available grassy areas.
- The student pilot experienced high levels of stress during the emergency, which likely hindered effective decision-making.
- The winch operator failed to perform a necessary inspection of the cable before starting flight activities.