What happened
On August 27, 2016, at approximately 14:00 local time, a Schleicher ASW-20 glider, registration D-2683, was involved in an accident during a winch launch at the Eduardo Castellanos de Villacastín aerodrome in Segovia, Spain.
The pilot had arrived at the aerodrome earlier that day and prepared the aircraft for flight. Due to a shift in surface wind direction, the takeoff was conducted from runway 12. The pilot coordinated the launch via radio with the winch operator and requested assistance from a club member to hold the wingtip during the initial takeoff roll.
Shortly after the glider lifted off the ground, the aircraft experienced a rapid increase in pitch angle. During this phase, the tow cable detached from the glider's hook due to the aircraft's geometry and high angle of attack. Following the detachment, the glider lost airspeed and entered a stall. The aircraft rolled heavily to the right and descended sharply. The impact occurred at an altitude of approximately 20 to 30 meters, with the nose of the aircraft striking the ground directly. The pilot sustained one serious injury to the lower extremities.
The investigation
The CIAIAC investigation examined the aircraft, the winch equipment, and the pilot's experience. The investigation noted that the winch, a Tost BB280, was functioning correctly and the cable itself had not broken, but had simply become unhooked.
Investigators analyzed the flight dynamics of the winch launch, noting that the acceleration in the first few seconds is much higher than in traditional aero-towing, requiring much faster pilot reactions. The investigation also reviewed the pilot's training, noting that while the pilot had completed winch training in a different glider model (Schleicher ASK-13), the performance characteristics of the Schleicher ASW-20 were significantly different.
Findings
- The primary cause of the accident was a takeoff maneuver that resulted in the premature release of the tow cable, leaving the glider with insufficient airspeed and an excessive pitch angle, which led to a loss of control.
- The pilot's limited experience with the specific performance characteristics of the Schleicher ASW-20 compared to the ASK-13 used during training contributed to the event.
- The pilot experienced a high workload and a sense of being overwhelmed by the flight variables during the critical moments of the launch.
- The aircraft sustained substantial damage to the fuselage and cockpit, and the wings showed cracks and wrinkles, leading to the aircraft being considered destroyed.