LS 3 spirals from a low turn in gusty bise wind

The pilot of an LS 3 was killed when the glider dropped into a tight spiral in a low turn in gusty bise wind near St-Imier and crashed into a wooded ravine; aircraft destroyed. Flying low in turbulence and apparently finding no lift, the pilot began a right turn that quickly tightened into a descending spiral, seen by a witness until it fell below the horizon. A bise gust off the broken terrain — a tailwind cutting lift as the glider neared the trees — and the aft-limit CG likely set it off. Autopsy showed a hard left-rudder input against the rotation, too low to recover. The loss of control was attributed to undetermined reasons.

1. Local soaring flight: After an aerotow launch from Courtelary and release near Tramelan, the pilot continued a local soaring flight in turbulent bise conditions in the St-Imier valley area.
2. Turbulent bise winds: A bise wind regime over the Jura created locally turbulent and gusty conditions with abrupt changes in wind intensity near the terrain.
3. Aft CG limit: The glider’s mass was within limits but the center of gravity was at the aft limit, making the aircraft more sensitive in pitch and potentially in stall and spin behavior.
4. Low-altitude turn in sink: Unable to find sufficient lift and flying low in the St-Imier valley, the pilot initiated a right turn, likely to interrupt the flight, at a height where margins were limited.
5. Uncontrolled spiral: A witness saw the glider suddenly roll until banked with its full wingspan visible, then enter a tight, descending turn, consistent with an inadvertent spiral or spin entry.
6. Rudder input applied: Autopsy evidence of a hard left rudder pedal input indicates the pilot attempted to counter the rotation, but had insufficient height to complete a recovery.
7. Crash - fatal: Still in a rotating descent, the glider struck treetops, inverted, and impacted the bottom of a wooded ravine, destroying the aircraft and fatally injuring the pilot.