Discus CS winglet catches in long grass on a winch launch in gusty Föhn conditions

The pilot of a Discus CS was seriously injured when it rolled inverted onto the runway during a winch launch. The launch was from a grass runway in Föhn conditions, the wind gusting to 37 kt. As the glider lifted off, its left winglet caught in grass more than 8 cm high, swinging it left about the vertical axis. Gusts of up to 32 kt amplified the yaw and added a roll, and the glider fell inverted from about 15 m. The tail boom broke off at the fin. The pilot was found to have sufficient winch and Föhn experience. He has no memory of the flight, which was reconstructed from eyewitnesses.

1. Winch launch on the grass runway: The glider was set up on the grass runway, the cable hooked on, and the winch driver opened up to full power after the cable was taut.
2. Föhn wind gusting to 37 kt: A Föhn weather situation was in place, with the wind from the south-east reaching 37 kt.
3. Left winglet catches in long grass: The wing runner released the right wing normally. As the glider lifted off, the left winglet caught in grass over 8 cm high.
4. Glider yaws left: The caught winglet swung the glider to the left about its vertical axis while it was still leaving the ground.
5. Gusts add a roll after lift-off: Once airborne, gusts of up to 32 kt strengthened the yaw and set up a rotation about the longitudinal axis as well.
6. Inverted impact from about 15 m: The glider fell inverted onto the grass runway from about 15 m. The tail boom broke off at the fin and the fuselage top behind the cockpit was badly damaged.