What happened
On November 25, 1965, a pilot departed from Kloten airport for a solo flight in a Piper PA-28-140 Cherokee, registration HB-OLD. The flight plan provided to authorities was notably vague, lacking both a specific destination and a defined route. After the aircraft failed to return to its origin, a large-scale search operation involving the Swiss Air Force and various rescue organizations was launched across northeastern Switzerland and into Germany.
The wreckage of the aircraft was not discovered until April 20, 1966, on the southeastern slope of the Goggeienberg in the Toggenburg region. Based on witness accounts and the location of the debris, the aircraft's flight path included several loops over various towns, eventually leading it toward the Swiss Alps. The pilot was killed in the impact.
The investigation
Investigators examined the wreckage and reconstructed the final moments of the flight. The investigation found that the aircraft's weight and center of gravity were within safe operating limits, and no mechanical failures or technical defects were identified in the engine, fuel system, or flight controls. The fuel tanks had ruptured upon impact, and the radio was still tuned to the Zurich Tower frequency.
Evidence from the wreckage indicated that the aircraft struck several pine trees before hitting the terrain. The investigation also noted that the pilot's flight experience was considered good, though his specific experience with this aircraft type was relatively limited at the time of the accident.
Findings
At the time of the accident, the region was experiencing significant weather instability, characterized by moderate mechanical turbulence near the terrain and gusty winds. Specifically, wind speeds at 1,500 meters were recorded at 10 knots with gusts up to 25 knots.
The investigation concluded that the pilot was flying at a dangerously low altitude near the mountain ridge. It is highly probable that the aircraft entered the lee-side turbulence created by the Goggeienberg ridge. This sudden loss of altitude caused the aircraft to strike trees and the ground. The investigation also considered the possibility that the pilot may have been momentarily blinded by the low angle of the setting sun, which could have contributed to the proximity to the ridge.