What happened
On December 17, 1962, a pilot conducting a personal reconnaissance flight departed Sion, Switzerland, in a Piper Cub J3C (HB-OAV). The flight was part of a training period focused on glacier landings. While navigating the region near the Grand St. Bernard, the pilot crossed the ridge between the Pointes de Molines and the Pointe des Rayons de la Madeleine.
During the transit, the aircraft encountered significant atmospheric turbulence. After initially losing altitude due to downdrafts on the southern slope, the pilot attempted to turn back and cross the ridge from south to north. However, while attempting to clear the ridge at an altitude of approximately 1,600 meters, the aircraft was struck by a powerful gust of wind, visible as a plume of blowing snow. This sudden turbulence caused a total loss of lift across the wings and tail, resulting in a stall. The aircraft plummeted and struck the southern slope of the Col de Menought, just 10 meters from the terrain, into a deep snowbank.
The investigation
The investigation examined the pilot's experience, the aircraft's mechanical condition, and the meteorological circumstances. The pilot, who had recently completed several glacier landings under instruction, was found to be in possession of his flying abilities at the time of the accident. The Piper Cub J3C was found to be in an airworthy condition, with its weight and center of gravity within prescribed limits. The investigation also reviewed the weather conditions, noting that while the weather in Valais was clear, high-altitude winds of 30 knots were present, and visible snow plumes indicated violent winds at the peaks.
Findings
- The pilot failed to utilize the established technique of crossing mountain passes diagonally, which would have allowed for a safer escape route if conditions deteriorated.
- The pilot did not maintain a sufficient safety altitude, likely violating minimum flight height regulations.
- The primary cause of the accident was the use of an improper flight tactic when attempting to cross a mountain pass during violent winds.
- The aircraft's sudden loss of control was triggered by severe wind gusts that caused a complete aerodynamic stall.
Safety action
No specific safety recommendations were recorded in the final report, though the investigation highlighted the necessity of using diagonal approaches to mountain passes to ensure a margin of safety during turbulent conditions.