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

While ridge soaring near the Montagne de Romont, the pilot of an ASK 18 was fatally injured when the glider flew into a wooded 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 as the light southwesterly gave way to a bise, making height hard to hold. In the shifting wind he lost margin of speed and/or terrain clearance and flew into trees; the impact attitude was undetermined. The cause was failure to hold safety margins; 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.