What happened
On July 21, 1961, a Sokol M-I C-s, registration HB-TAB, departed from Bern-Belp airport for a flight to Nice, France. The flight, which included the pilot and two passengers, was delayed by approximately one hour from its original schedule. During the flight, the aircraft approached the Gemmi Pass from the direction of Kandersteg.
As the aircraft navigated the terrain, it entered a valley area south of the Schwarenbach mountain inn. While performing a steep left turn around a rock spur, the aircraft struck rising terrain at the Seestutz, north of the Daubensee, at an altitude of 2,190 meters. The impact resulted in three fatalities and the total destruction of the aircraft, which subsequently caught fire.
The investigation
The investigation examined the aircraft's technical condition, the pilot's experience, and the prevailing meteorological conditions. The Sokol M-I C-s was found to be approximately 25 kg over its maximum takeoff weight at the time of departure. The pilot was described as an experienced and reliable aviator with approximately 150 hours of total flight time, including several Alpine operations.
Investigators analyzed the flight path and the weather, noting a north-stagnation pattern over the Alps with cloud bases rising toward the mountain crest. The investigation also looked into the pilot's decision-making process regarding altitude and terrain clearance during the approach to the pass.
Findings
- The aircraft was flying at an altitude of approximately 2,200 meters, which was insufficient to clear the Gemmi Pass summit of 2,316 meters.
- The pilot entered a terrain pocket without sufficient visibility or oversight, leaving no possibility for a timely return or an emergency landing.
- Time pressure resulting from the initial departure delay likely influenced the pilot's decision to fly at a lower altitude.
- The aircraft's weight exceeded the maximum allowable takeoff weight by roughly 25 kg, which may have hindered the climb performance.
- There was a possibility that the pilot misidentified landmarks due to the obscured terrain, potentially mistaking the Schwarenbach area for a different part of the pass.