What happened
On June 7, 2020, a Schleicher ASK 21 glider, registration OY-KXF, was performing a winch-assisted takeoff from runway 28 at Gesten Airfield. The aircraft was occupied by a flight instructor and a student pilot for a training flight under visual flight rules (VFR).
During the initial climb, approximately 10 to 15 meters above the ground, the instructor noticed that the winch cable had become slack and the aircraft was no longer being pulled forward. The instructor immediately moved their hand from the airbrake lever to the release handle to disconnect the glider from the cable.
At that precise moment, the student pilot fully deployed the airbrakes and pushed the control stick all the way forward. Although the instructor managed to retract the airbrakes, they were unable to recover the aircraft's pitch before the nose struck the ground at a steep angle. The impact caused the aircraft to bounce, traveling 16 meters before the main wheel and right wing hit the ground, and continuing for another 13 meters before coming to a final stop approximately 258 meters from the takeoff position.
The investigation
The investigation focused on the sequence of events during the launch and the physical damage to the aircraft. Investigators examined the fiberglass fuselage, noting delamination, cracks, and breaks in the cockpit area and nose section. The impact also caused the plexiglass canopy to disintegrate and separate from the airframe. Damage was also identified on the rudder and both the horizontal and vertical stabilizers. Both the instructor and the student pilot confirmed that there were no mechanical or technical failures with the Schleicher ASK 21 prior to the incident.
Findings
- The primary cause of the accident was the uncoordinated control inputs by the student pilot, specifically the simultaneous full deployment of airbrakes and forward stick input during a critical phase of the launch.
- The instructor's attempt to disconnect from the slack winch cable occurred simultaneously with the student's actions, preventing an effective recovery of the aircraft's attitude.