What happened
On March 15, 1962, at 14:42 CET, a Meta Sokol L-40, registration HB-TAW, departed from Zurich-Kloten airport. The pilot, accompanied by a passenger, intended to fly a business route over the Alps toward Agno. Despite receiving a weather advisory from the airport weather service indicating that a visual flight rules (VFR) flight over the Alps was impossible due to heavy cloud cover and snow, the pilot proceeded with the flight.
At approximately 15:00, the aircraft emerged from a solid cloud layer at an altitude of roughly 1,20 and immediately broke apart in mid-air. Witnesses near Menzingen reported hearing a sudden increase in engine noise followed by the sight of the aircraft disintegrating. The aircraft crashed into a forested area, resulting in two fatalities.
The investigation
The investigation examined the aircraft's structural integrity, the pilot's recent training history, and the meteorological conditions. Because the investigation sought to rule out manufacturing defects, Czechoslovakian civil aviation authorities were invited to provide an observer.
Investigators analyzed the wreckage and found no evidence of mechanical failure, material defects, or fatigue. The engine was found to be in working order and could be repaired. The investigation also reviewed the pilot's recent flight training, noting that he had only recently passed a renewed private pilot check-ride and was operating an aircraft for which he had not yet received his updated physical license. The investigation also noted that the aircraft was not equipped for instrument flight, lacking a horizon indicator, directional gyro, or variometer.
Findings
- The primary cause of the accident was an excessive exceedance of the permitted load factors and speed limits.
- The aircraft likely experienced a structural failure of the left wing due to high stress during an attempt to pull out of a dive or level off at the cloud base.
- The pilot was operating in a weather situation that was incompatible with his training, the aircraft's certification, and the available instrumentation.
- The pilot's decision to fly despite known adverse weather and the lack of instrument capability led to an overestimation of his ability to navigate the terrain safely.