What happened
On July 13, 197 and, a pilot and his son were conducting a recreational flight through the Alps in a Blanik L-13 glider, registration HB-1049. After taking off from Sion, the flight proceeded through various thermal currents, reaching altitudes near the Wildhorn. As the available lift dissipated, the pilot began a descent toward Vernamiège, utilizing a series of turns and spirals along the mountain slope.
While flying at a low altitude near the Mayens de Vernamiège, the aircraft performed two right-hand spirals. A witness on the ground observed the glider at an altitude of approximately 100 meters, noting that the aircraft appeared to be spiraling close to the terrain. Following the second turn, the glider entered an accelerated dive. The aircraft struck the ground with its right wingtip, followed by the nose and the left wingtip, after rotating approximately half a turn. The impact caused the fuselage to break significantly behind the cockpit.
The investigation
The investigation examined the flight path, the aircraft's mechanical condition, and the pilot's maneuvers. Investigators reviewed the pilot's extensive experience, noting his proficiency in mountain flying and his familiarity with the local terrain. The technical inspection of HB-1049 found no evidence of pre-existing mechanical defects that could have contributed to the crash. Meteorological data confirmed favorable flying conditions, characterized by clear skies and light, variable winds.
Findings
- The pilot was performing spirals at a low altitude in close proximity to a steep, 33% to 40% gradient slope.
- Executing such maneuvers near a steep terrain is inherently difficult due to the loss of a stable horizon for reference.
- The pilot's attention may have been divided between maintaining flight parameters and observing objects on the ground.
- There is a known tendency during turns near a slope to unconsciously tighten the radius by increasing bank angle, which simultaneously reduces airspeed and increases the stall speed.
- Insufficient airspeed reserve during these maneuvers led to a stall and subsequent loss of control.
Safety action
No specific safety recommendations were recorded in the final report.