What happened
On July 25, 2020, a Cessna 172R, registration HB-TLF, was conducting a private sightseeing flight in the Swiss Alps. The flight, organized as part of a scenic tour for business clients, departed from Reichenbach airfield. The pilot had planned a modified route to allow more time to reach recommended altitudes by flying in the reverse direction of the standard tour.
During a climb through the Lötschental region, the aircraft's airspeed steadily decreased. Witnesses on the ground reported hearing unusual, oscillating engine noises and observing the aircraft in a spinning motion. At approximately 12:19 PM, the aircraft struck a rock face below the Gletscherspitza at an altitude of roughly 2,600 meters. The impact caused a fire, and all four fatalities occurred upon impact.
The investigation
An investigation by the Swiss Transportation Safety Investigation Board (SUST) focused on the aircraft's performance and weight calculations. Investigators found that the pilot had estimated the passenger weights without actually weighing them, instead using estimated values in the loading manifest. This led to a significant discrepancy between the recorded and actual weights.
Furthermore, the investigation examined the aircraft's center of gravity and its operational limits. The investigation also looked into the pilot's familiarity with recovery procedures for unusual flight attitudes and the suitability of the aircraft type for the specific mission requirements.