What happened
On August 11, 1961, a Piper J3C aircraft, registration HB-ONZ, departed from Agno, Switzerland, for a flight to Zurich. While the initial departure occurred during favorable weather conditions, the atmospheric state in the Alps was characterized by a significant northern stau situation, resulting in heavy cloud cover and fog in certain areas.
At approximately 15:30, the aircraft was flying southeast at an altitude of nearly 2,200 meters. The aircraft entered a steep dive of approximately 30 degrees, slightly banked to the right, and struck a slope on the Gross-Tisch near the Rosstock. The impact occurred at an angle of roughly 70 degrees against the steeply inclined terrain. The collision resulted in one fatality (the pilot) and the total destruction of the aircraft.
The investigation
The investigation examined the flight path, weather conditions, and the pilot's qualifications. It was noted that a preceding flight in a different aircraft had successfully navigated around the weather by flying east through the Rheintal and Walensee. The investigation also reviewed the technical condition of HB-ONZ, finding no evidence of mechanical failure or technical defects. The aircraft was not equipped with instrument flight capabilities.
Findings
- The pilot likely initially followed a route similar to the preceding aircraft but chose to continue north toward the mountains instead of diverting east to avoid the deteriorating weather.
- The pilot encountered dense fog and cloud cover that rendered visual flight conditions impossible.
- The pilot lacked both the necessary instrument equipment and the specific training required to navigate in such low-visibility conditions.
- The primary cause was the pilot's decision to fly into a weather situation that no longer met the requirements for visual flight rules (VFR).