What happened
On July 29, 2012, a Schleicher ASW 19 glider was performing a winch launch at the Kirn Gliding Field. The takeoff appeared normal to witnesses until the aircraft reached the release altitude. At this point, the winch operator ended the tow, but the glider failed to disconnect from the tow cable.
Upon realizing the release had failed, the winch operator attempted to use the cable cutter mechanism, but this device also failed to function. The pilot notified the flight controller via radio, requesting that the cable be cut, but was informed that such an action was not possible. To prevent the cable from becoming taut and pulling the aircraft, the pilot attempted to maintain a position near the winch. As the aircraft approached the ground, the tow cable became entangled in a group of bushes. This snagged the aircraft, pulling it to the ground from a height of approximately 5 meters. The impact caused the fuselage tube to break, though the pilot escaped without injury.
The investigation
Investigators examined the release mechanism and the winch equipment. During a reconstruction of the coupling event, it was determined that a pair of double rings had become hooked in a gap adjacent to the release opening. The investigation found that a visual inspection of the ring position could have identified this improper connection.
Furthermore, an inspection of the winch (RP-8135) revealed that the cable cutting system was defective. While the winch had undergone a periodic inspection in March 2012, the mechanism failed to sever the cable during the accident.