What happened
On September 1, 1967, a Cessna 170 B, registration HB-CRH, departed Locarno on a private flight destined for Basel. The aircraft was carrying the pilot and three passengers. During the flight, the aircraft traversed the high Alps, passing over the Goms region and the Great Aletsch Glacier.
As the flight progressed, the pilot encountered increasing cloud cover and fog. While attempting to navigate the complex terrain of the Bernese Alps, the aircraft disappeared from radar and failed to arrive at its destination. Following a search operation that utilized aircraft and helicopters, debris and remains were discovered near the Eismeer station of the Jungfrauberry railway, having been moved by avalanches from a higher impact site on the southeast face of the Eiger.
The investigation
The investigation focused on the pilot's flight planning, the meteorological conditions, and the aircraft's performance. Investigators examined weather reports from the Jungfraujoch meteorological station and testimonies from witnesses, including a glacier pilot and a mountain guide, who reported hearing an aircraft in the area during periods of heavy fog and low visibility.
Physical evidence was limited due to the extreme terrain and subsequent avalanches, but recovered fragments, including an engine component and a deviation table bearing the registration HB-CRH, confirmed the identity of the wreckage. The investigation also reviewed the pilot's recent training, noting he had completed transition training on this specific aircraft only a few weeks prior.
Findings
- The pilot attempted to cross the high Alps under unfavorable weather conditions that were not conducive to safe Visual Flight Rules (VFR) operations.
- The aircraft likely encountered severe turbulence or downdrafts while attempting to pass through the Eiger saddle, which may have forced the plane into clouds or prevented it from avoiding the rock face.
- The pilot may have been pressured by time, as the flight schedule was tight, potentially leading to the decision to fly a direct route over the massif rather than a safer detour through the Rhone Valley.
- The aircraft was heavily loaded, with a weight of approximately 980 kg, near its maximum limit of 1000 kg.
- Conditions for structural icing were present in the accident area, and carburetor icing cannot be ruled out as a contributing factor.
- The pilot likely lost visual reference with the terrain due to the onset of fog and clouds, leading to a frontal collision with the mountain.