What happened
On July 21, 2015, at approximately 17:00 local time, a Scheibe Flugzeugbau Bergfalke IV glider was performing a winch launch from runway 27 at the Gardelegen airfield. Shortly after reaching an altitude of approximately 10 meters, the pilot disconnected from the cable because the tension from the winch rope had decreased.
Following the disconnection, the glider experienced two hard landings on the runway. Witnesses observed the aircraft perform a ground loop, rotating 180 degrees before coming to a stop in the direction opposite to the initial takeoff. The accident resulted in two serious injuries and heavy damage to the aircraft.
The investigation
The BFU examined the aircraft, the winch mechanism, and the flight sequence. The investigation focused on the cause of the loss of tension in the cable and the subsequent loss of control during the launch. Physical inspection of the Bergfalke IV revealed damage to the underside of the forward fuselage near the main wheel, as well as cracks on the upper surfaces of the wingtips near the airbrake housings. Damage was also identified in the elevator and airbrake control linkages, consistent with the hard landings.
Regarding the winch equipment, investigators examined a Busio-type winch mounted on a truck chassis. The winch utilized six side-by-side cable drums. The investigation focused on the state of the Dyneema towing rope and the drum mechanism during the launch.
Findings
- The primary cause of the accident was a mechanical failure of the winch cable management, specifically a loop of the previously used cable jumping over the side of the drum.
- This loop became wrapped around the main drive shaft that powers all six drums, causing the mechanism to block.
- This blockage led to the sudden loss of tension in the tow rope, prompting the pilot to disconnect at a low altitude.
- The subsequent hard landings and ground loop were a direct result of the loss of upward momentum and tension during the critical takeoff phase.