What happened
On July 18, 2020, at approximately 16:00 local time, a single-seat Alexander Schleicher ASW 28-18 glider departed from the Bonn-Hangelar airfield (EDKB) for a thermal flight using a winch launch. The aircraft initially climbed normally to an altitude of approximately 50 meters. As the winch operator increased the climb angle, the aircraft reached an altitude of between 100 and 120 meters when the tow cable snapped. Witnesses observed the cable falling to the ground, followed by the release of the glider's front attachment.
Following the loss of tension, the glider failed to maintain a normal flight attitude. Instead, the aircraft pitched nose-down into a steep descent characterized by a spinning or stalling motion. The aircraft struck the ground approximately 250 meters east of the takeoff point. The impact, which initially involved the left wing, resulted in serious injuries to the pilot and caused extensive damage to the aircraft, including a broken fuselage, a detached tail unit, and a detached left wing.
The investigation
The BFU investigation focused on the mechanical integrity of the launch equipment and the flight performance of the aircraft. Investigators examined the tow cable and found a broken release mechanism (the designated weak link). The aircraft's technical condition was reviewed, and no mechanical defects were found in the Alexander Schleicher ASW 28-18. The investigation also confirmed that the aircraft's weight and balance were within permissible limits, with the pilot's weight supplemented by ballast to maintain the required center of gravity. The pilot's licenses, medical certification, and flight experience were also verified.
Findings
- The primary cause of the accident was the failure to maintain sufficient airspeed for level flight following the sudden loss of tow tension, which led to a stall.
- The pilot was unable to recover from the resulting nose-down pitch due to a lack of altitude reserve.
- Contributing factors included the pilot's limited experience with this specific aircraft model and the pilot being overwhelmed by the sudden emergency situation during the launch interruption.