What happened
On July 23, 1968, a Piper Cherokee PA-28-140, registration HB-OYE, departed Zurich-Kloten for Lugano-Agno. The flight began as a planned visual flight rules (VFR) operation. Early in the flight, the pilot provided several position reports, climbing through various altitudes near Brunnen, Altdorf, and Erstfeld. However, after passing Erstfeld, the flight progress slowed significantly.
As the aircraft approached the Gotthard Pass, it encountered dense fog and heavy mist. Witnesses near the north ramp of the pass observed the aircraft flying under a low cloud ceiling. Shortly thereafter, a patrol member reported seeing the aircraft at an extremely low altitude—estimated at only 50 meters—navigating through thick fog with visibility fluctuating between 10 and 100 meters. Following the sighting, a high-speed impact was heard near the pass. The aircraft struck the terrain with great force, causing a post-crash fire that destroyed the wreckage. The pilot was killed in the accident.
The investigation
The investigation examined the aircraft's condition, the meteorological environment, and the pilot's flight path. Investigators found that the aircraft's vacuum-driven instruments, including the artificial horizon and directional gyro, were non-functional due to a previously noted pump failure. However, there was no evidence of mechanical failure or pilot health issues contributing to the crash.
Meteorological analysis revealed that while the forecast suggested better conditions, a compact cloud layer was actually situated between 2,000 and 3,000 meters over the Ticino region, effectively closing the pass for VFR flight. The investigation also noted that other pilots in the area had observed similar low ceilings and had elected to divert their routes to avoid flying into the clouds.
Findings
- The pilot attempted to continue an Alpine flight under insufficient visibility conditions for VFR flight.
- The aircraft entered a zone of heavy fog and low cloud cover at the Gotthard Pass, where the pilot likely lost spatial orientation.
- The low altitude of the clouds and the presence of moving fog patches may have led the pilot to believe the visibility issues were only localized and temporary.
- The loss of orientation was exacerbated by the fact that the magnetic compass becomes unreliable during tight turns in such environments.
- The aircraft struck the ground in a steep dive, resulting in the total destruction of the airframe.