What happened
On August 20, 1965, a pilot operating a Karpf-Baby glider, registration HB-499, departed from Winterthur airfield to perform a cross-country flight toward Altenrhein. During the flight, the thermal lift conditions began to weaken significantly. As the pilot encountered nearly no rising air, he was forced to execute an off-field landing near Niederhelfenschwil/SG.
While descending, the pilot initially identified a landing site near Tüfi but abandoned that choice due to a row of trees obstructing the approach. At an altitude of approximately 200 meters, he selected a different, slightly rising meadow. During the final approach, the aircraft crossed a high-voltage power line at a height of roughly 10 meters. Due to a moderate tailwind, the aircraft's ground speed remained high, causing the landing to be excessively long. The glider touched down approximately 20 meters before a path, skidded across the ground, and crossed a small road where it struck a wire fence. In an attempt to avoid an apple tree, the pilot maneuvered to the right, but the left wing ultimately collided with the tree trunk.
The investigation
Investigators examined the flight conditions and the pilot's decision-making process. The investigation established that the pilot did not finalize his landing site selection until he was at an altitude of 200 meters, which is below the recommended threshold of 300 meters for such decisions. The investigation also noted that the chosen landing area was constrained by obstacles, including a wooded ridge and power lines, and that the prevailing wind conditions contributed to the difficulty of the maneuver.