What happened
On August 23, 2023, an Alexander Schleicher ASK 21 glider was performing a winch launch at the Rheinstetten glider airfield. The flight began normally, but during the second launch attempt of the session, the aircraft failed to gain sufficient altitude.
As the glider was at a low altitude, the winch operator reduced the power of the electric winch. This reduction in power caused the tension in the cable to drop, leading to the cable detaching from the aircraft. Following the separation, the glider entered a steep descent. The pilot was unable to arrest the descent, and the aircraft struck the ground nose-first. The impact caused the nose wheel to hit the ground first, followed by a secondary impact and a sliding motion through the grass. The pilot and the passenger sustained serious injuries, including spinal and chest injuries.
The investigation
The BFU investigation examined the sequence of events, the winch operations, and the aircraft's flight data. Investigators reviewed the statements from the pilot, the passenger, the launch director, and the winch operator. The investigation also analyzed the flight path using data from the aircraft's FLARM collision warning device, which provided GPS and barometric altitude information.
Physical inspections of the ASK 21 revealed cracks in the landing gear fairing, but no structural damage to the airframe or control surfaces. The investigation also examined the state of the electric winch and the Dyneema launch cable. The winch operator reported hearing a loud noise, which he interpreted as a cable break, coinciding with his decision to reduce the winch's power via the controller.