What happened
On August 4, 1971, at approximately 12:45 PM, a L-Spatz 55 glider, registration HB-627, departed from Courtelary for a cross-country flight via tow. After flying along the southern Jura foothills, the pilot reached the vicinity of Olten at an altitude of approximately 700 meters. Unable to locate the Olten airfield, the pilot continued toward Lostorf.
Upon reaching Lostorf at an altitude of 300 meters, the pilot selected a slightly elevated, sloped plateau south of the town as an alternative landing site. During the approach, the aircraft crossed a high-voltage power line at high speed. While performing a side-slip with airbrakes fully extended to clear a wooded area, the pilot failed to maintain adequate airspeed. As the aircraft leveled out near the ground, the speed had increased to approximately 100 km/h. The pilot attempted to land on a meadow sloping downward at a 2.5-degree angle. Near the end of the field, the pilot retracted the airbrakes and pulled up before a 25-meter-wide cornfield. At approximately 14:10, the tail of the glider struck 1.3-meter-tall corn stalks, causing the aircraft to crash into an adjacent field.
The pilot sustained no injuries, but the L-Spatz 55 was heavily damaged. There was minor damage to third-party property.
The investigation
The investigation examined the aircraft's airworthiness, the pilot's experience, and the environmental conditions. The HB-627 was found to be in a fully airworthy condition with valid certification. The pilot, a German national with 41 hours of flight time, held a valid glider license and showed no signs of medical impairment. Weather conditions at the time included scattered clouds with bases between 1500 and 2000 meters, good visibility, and light, variable winds.
Findings
Several factors contributed to the accident:
- The approach was complicated by the presence of a high-voltage power line and a wooded area.
- A slight tailwind negatively impacted the landing.
- The pilot lost control of the airspeed during the side-slip maneuver.
- The pilot's limited flight experience contributed to an inability to manage the tactical and aerodynamic challenges of the sloping landing site.