Cirrus 18 incident near Löhningen during thermaling attempt
On September 1, 1985, a Schempp-Hirth Cirrus 18 experienced an incident near Löhningen, Switzerland. The pilot, intending to land at Schaffhausen airfield, encountered weak thermals and began spiraling at approximately 1000 meters altitude. The glider suddenly entered a spin, and despite the pilot's efforts, the rotation could not be stopped. The aircraft descended almost vertically into a forest, resulting in the destruction of the glider and serious injuries to the pilot. The report confirmed the accident was caused by the glider's speed dropping below the minimum during thermaling in turbulent conditions.
- Aerotow local soaring: The pilot aerotowed from Bohlhof for a local soaring flight toward the Randen area, reaching a maximum altitude of about 1350 m MSL.
- Marginal weak thermals: In the Chornberg area the thermals were weak to moderate, poorly usable, and accompanied by gusty winds up to 20 kt, leading to a gradual loss of height.
- Limited height margin: Near Chornberg the pilot realized he no longer had sufficient altitude to return to Bohlhof and instead planned to land at Schaffhausen airfield, with only about 540 m height above it.
- Slow circling in lift: At about 1000 m MSL the pilot began thermaling turns in weak, gusty lift at an indicated airspeed of roughly 90–100 km/h, close to minimum speed.
- Stall and spin entry: While circling in the weak, turbulent thermal the glider suddenly rolled left, stalled, and entered a spin.
- Failed spin recovery: The pilot attempted to stop the rotation but was unable to recover fully, with witnesses observing several turns, a brief cessation of spinning, and a roll-like motion to the right.
- Crash - serious injury: The glider descended almost vertically into a forest near Chornberg, destroying the aircraft and seriously injuring the pilot.