What happened
On June 5, 1962, at approximately 19:00 CEST, a Sokol M-1D aircraft, registration HB-TAO, departed from Montreux-Rennaz for a return flight to Zurich. The pilot was accompanied by one passenger. During the climb, the aircraft flew toward the Col de Jaman at an altitude of only 80 to 100 meters above the ground. As the aircraft approached the pass, it encountered strong and gusty downdrafts. Approximately 1.5 kilometers before reaching the pass summit, the aircraft suddenly rolled over one wing and entered a steep descent. The impact resulted in two fatalities and the total destruction of the aircraft.
The investigation
The investigation examined the flight conditions, the aircraft's mechanical state, and the pilot's actions. Witnesses observed the aircraft struggling against heavy winds and being buffeted by gusts. Examination of the wreckage revealed that the landing gear and flaps were retracted and the propeller deformation suggested the engine was at a high RPM at the moment of impact. No technical defects were found in the Sokol M-1D.
Findings
- The primary cause of the accident was a loss of airspeed leading to an aerodynamic stall.
- The pilot attempted to fly through a mountain pass in a climbing configuration with insufficient altitude margin.
- Strong, gusty downdrafts from the northeast contributed to the loss of lift and may have masked the aerodynamic warnings of an impending stall.
- The pilot's decision to maintain a low altitude while navigating terrain prone to heavy turbulence increased the risk of the accident.