What happened
On October 19, 1968, at approximately 14:10, a Blanik L-13 glider, registration HB-882, was performing aerobatic training maneuvers under the supervision of a flight instructor near the Schänis airfield. The flight sequence included several maneuvers, including a spin, a loop, and a loop-the-loop (renversement). Following these maneuvers, the pilot attempted a series of left-hand spirals.
During the descent, the aircraft entered a steep left-hand spiral that the pilot could not recover from. As the aircraft continued to bank and descend, it struck the ground approximately 3 km north of the airfield on a meadow. The impact first involved the left wingtip, followed by the forward fuselage. The aircraft was destroyed, and the pilot sustained serious injuries.
The investigation
The investigation, conducted in collaboration with the St. Gallen Cantonal Police, examined the aircraft's mechanical condition and the pilot's flight performance. Investigators reviewed the aircraft's maintenance history, noting previous repairs to the control consoles and wing structures following prior incidents.
Technical analysis of the wreckage focused on the aileron control mechanism. While investigators found some friction caused by a misplaced electrostatic discharge cable, they determined this resistance was minimal and could be overcome by hand. The investigation also looked into whether the control surfaces were obstructed by cockpit cushions or if a mechanical failure in the aileron linkage had occurred. Reconstructive flight tests were also performed to determine if specific flight attitudes could lead to a loss of control.
Findings
- The pilot was unable to recover the aircraft from a steep spiral for reasons that could not be definitively established.
- The aircraft entered a left-hand turn that led to ground contact.
- While a mechanical blockage of the aileron linkage could not be entirely ruled out under extreme stress, no definitive pre-existing defect was found.
- Flight tests suggested that in certain high-bank configurations, the aircraft might resist recovery even with significant control input.
- The pilot had not flown the aircraft for nearly three months prior to the accident, which may have impacted the execution of complex maneuvers.