Mini Nimbus strikes trees soaring low along a forested slope

The pilot of a Mini Nimbus C was fatally injured when the glider struck trees and rocky terrain while soaring low along a forested slope near Zweisimmen; aircraft destroyed. On a local mountain flight late in the afternoon, with thermals weak and turbulent, the glider's right wing brushed the treetops; it yawed sharply right, the left wing struck a fir about 10 m up, and fell onto the slope. No one saw it; the wreckage showed a normal attitude, not a stall, and no technical or medical cause was found. Terrain contact likely came while working marginal lift close to the slope, perhaps after a turbulence upset; the cause was left undetermined.

1. Aerotow local soaring: The Mini Nimbus C launched by aerotow from Zweisimmen at 15:45 for a local soaring flight and released at about 2000 m MSL on slopes east of the airfield.
2. Weak, turbulent thermals: By late afternoon the thermals were weakening and the accident area was characterized by pronounced local turbulence and abrupt vertical air movements.
3. Low, close-in ridge flying: The pilot flew down-valley close to a steep, forested slope near the Spillgerten massif, likely seeking weak remaining lift in a hillside terrain pocket.
4. Right wing hits trees: The glider's right wing first grazed treetops on the steep Mulebergwald slope while still in a normal attitude, showing insufficient clearance from terrain.
5. Violent impact with tree: Strongly decelerated and yawed right, the glider's left wing then struck a large fir trunk about 10 m above the ground, stopping abruptly and sliding down it.
6. Crash - fatal: The glider then impacted the rocky, debris-strewn slope nearly parallel to the terrain, destroying the forward fuselage and fatally injuring the pilot.