What happened
On October 30, 1971, a Cessna 172 F, registration HB-CMR, was conducting a private visual flight from Bern-Belp to Lugano-Agno. After a one-hour stop in Agno, the pilot departed at 14:51 for the return leg to Bern with three passengers on board. During the flight, the pilot attempted to contact Bern Tower multiple times between 15:47 and 15:48, but the ground station's responses were not heard. Witnesses near Alp Winterberg reported seeing the aircraft flying at a low altitude with reduced engine power through heavy fog. At 15:52, the aircraft struck the heavily forested northwest slope of the Sigriswilergrat at an altitude of 1,330 meters. The impact resulted in four fatalities and the total destruction of the aircraft.
The investigation
Investigators examined the pilot's preparation and the meteorological conditions at the time of the accident. The pilot had checked the weather in Bern earlier that morning and noted a forecast for clearing fog, which led to an optimistic outlook for the flight. However, the investigation established that the pilot did not seek updated weather information regarding the northern Alps during the stop in Agno, despite noting that the weather was "not particularly good." The investigation also reviewed the aircraft's mechanical state, finding that the engine and propeller were properly maintained and that the weight and balance were within limits. While there had been reports of engine issues in some Cessna 172 models, the investigation found no evidence of mechanical failure in this specific instance.
Findings
- The pilot was flying under visual flight rules (VFR) and was not trained or authorized for instrument flight rules (IFR).
- The aircraft unintentionally entered a layer of clouds while the pilot was likely attempting to find a descent path through wavy, uneven fog.
- Inadequate flight preparation, specifically the failure to obtain updated weather briefings during the intermediate stop, contributed to the accident.
- Potential errors in judgment by the relatively inexperienced pilot may have played a role in the loss of situational awareness.