What happened
On May 22, 1966, a Piper PA-18 A "Super Cub", registration HB-OPE, was engaged in a supply mission to the Monte-Rosa hut. After successfully delivering supplies from Sion, the pilot traveled to the Riffelberg station area (near Zermot-Gornergrat) to collect additional cargo.
Upon arriving at the Riffelberg site, the pilot intended to perform a short training flight before beginning the loading process. The aircraft landed on hard, frozen snow in a slight depression near the station. During the turn to stop the aircraft, the plane began to skid to the left. Fearing the aircraft would drift too low on the slope, the pilot applied full power for an immediate takeoff attempt without first resetting the flaps to the standard takeoff position.
During this rapid departure, the aircraft drifted toward the right side of the slope. Despite the pilot's efforts to correct the course with heavy left rudder, the aircraft struck a rocky embankment with its ski and right wing. The impact caused the aircraft to somersault before coming to rest in the depression. The two occupants sustained only superficial injuries.
The investigation
The investigation examined the pilot's experience, the aircraft's mechanical condition, and the environmental factors at the time of the accident. The pilot held a valid private pilot license with mountain landing extensions and had significant experience in mountain flying, though the Riffelberg landing site was unfamiliar to him.
Technical inspections of the Piper PA-18 A "Super Cub" revealed no mechanical failures in the engine or airframe. The aircraft was properly equipped with skis for glacier operations and was in good airworthiness condition. Investigators also analyzed the terrain and local meteorological data, noting that while the weather was generally good, local wind conditions were present.