What happened
On July 8, 1972, a Cessna 172, registration HB-CBN, departed from Ascona aerodrome for a private flight. The aircraft was carrying the pilot and three passengers. Following a departure from runway 17, the pilot performed a wide left turn while climbing over Lake Maggiore, heading toward the entrance of the Verzasca Valley.
While maintaining a low altitude in a climbing turn, the pilot entered a narrow, dead-end valley, mistakenly believing it would lead to the Maggia Valley. Upon realizing the navigational error, the pilot attempted to maneuver but was unable to turn around. The aircraft entered a stall and struck trees on the southwest slope of the valley. The aircraft came to rest horizontally at an altitude of approximately 1,000 meters. The impact resulted in the destruction of the aircraft, though the pilot sustained only minor injuries and the three passengers were uninjured.
The investigation
The investigation established that the pilot held a valid private pilot license but had limited flight experience, totaling approximately 40 hours, with only 5.21 hours on this specific aircraft type. For the outbound leg of the flight, a passenger with 96 hours of experience had assisted with navigation, though that individual's pilot license had expired.
Technical inspections of the Cessna 172 revealed no pre-existing mechanical deficiencies. The aircraft's weight and center of gravity were within permissible limits at the time of the accident. Meteorological conditions were favorable, with visibility of 20 km and scattered clouds at 2,500 meters.
Findings
- The flight for the return leg lacked adequate preparation, and no specific flight path had been established.
- There was no clear definition of task distribution between the pilot and the passengers for the return journey.
- The pilot's insufficient flight altitude when entering an unfamiliar valley left no margin for error or maneuvering.
- The pilot relied on a passenger for navigation during the outbound leg, but failed to personally ensure adequate navigational preparation for the return flight.