What happened
On July 16, 1967, a Piper PA-28-140, registration HB-OLM, was conducting an Alpine flight over the Jungfrau region. The pilot, flying with two passengers, attempted to cross the Alpine ridge via the Unter-Mönchsjo/Ober-Mönchsjo passes by flying through the Ewigschneefeld glacier basin.
While flying at a low altitude—estimated by the pilot to be approximately 100 meters above the ground—the aircraft entered a section of the glacier with a significant upward slope. As the terrain rose, the aircraft's climb performance proved insufficient to maintain altitude. The pilot noted the stall warning light illuminating several times. Realizing the danger, the pilot attempted a turn but found the airspeed too low to execute a safe banking maneuver. To avoid a stall during the turn, the pilot leveled the wings, but the aircraft subsequently lost altitude and settled into the soft snow of the glacier. The three occupants sustained light injuries.
The investigation
The investigation examined the pilot's experience, the aircraft's technical condition, and the environmental factors at the time of the accident. The pilot had approximately 43 total flight hours, with only 17 hours specifically in the Piper PA-28-140, and lacked specialized experience in mountain or glacier flying.
Technical inspections of HB-OLM revealed no mechanical defects. Weather conditions were favorable, characterized by clear skies, good visibility, and light winds. The investigation focused on the pilot's flight path, the aircraft's climb capabilities relative to the 1:15 gradient of the glacier, and the visual illusions caused by the uniform white terrain.