ASK 18 pilot flies into a Jura slope after losing his safety margins in weak lift

The pilot of an ASK 18 was fatally injured when the glider struck a wooded Jura slope; aircraft destroyed. The unobserved wreck was found two days later. On his first solo of the season, after a 7-month lay-off, the pilot released at ~1000 m over the Grenchenberg and worked the Jura ridge east. Lift was weak and sparse as the light southwesterly gave way to a bise, making height hard to hold. In the shifting wind he lost adequate margin of speed and/or terrain clearance and flew into trees; the impact attitude could not be determined. The cause was failure to hold safety margins in the changing wind; limited recent practice contributed.

1. Aerotow local flight: The pilot took off from Grenchen by aerotow for a local training flight and released over the Grenchenberg before ridge-flying along the Jura towards the east.
2. Limited recent soaring: This was the pilot’s first solo glider flight of the season after a 7‑month break from soaring, with only a brief dual check flight 12 days earlier and modest experience on the ASK 18 type.
3. Marginal ridge conditions: Along the Jura the wind was changing from weak southwesterly to bise with sparse and weak lift on the ridge, making height maintenance difficult.
4. Insufficient safety margins: While flying near the Jura slope, the pilot did not maintain adequate safety margins in airspeed and/or distance from the terrain under the prevailing variable wind conditions.
5. Loss of safe flight path: The inadequate margins led either to sink close to the slope or to an unrecognized low-speed, over-banked or stalled condition from which recovery was not possible at that height.
6. Crash - fatal: The glider impacted a wooded slope on the Montagne de Romont at about 1130 m MSL, was destroyed, and the pilot sustained fatal injuries.