What happened
On January 9, 1974, a Beagle Pup B 121, registration HB-NAD, departed Grenchen Airport for a planned VFR flight to Bern-Belp. The pilot was flying in formation with another aircraft of the same type, HB-NAC. During the flight, the pilots monitored the weather via radio and noted changing conditions in the Bern area.
As the flight progressed, the pilots encountered worsening visibility. While attempting to navigate via the city of Bern to avoid difficult terrain, the pilot of HB-NAD decided to abort the approach to Bern and return to Grenchen. During the execution of a right-hand turn to head back, the aircraft entered a dense layer of fog. At approximately 15:44, the Beagle Pup B 121 struck trees at the edge of a forest near the Bannholz area, north of Habstetten. The impact resulted in the death of the pilot and the total destruction of the aircraft.
The investigation
The investigation, conducted alongside the Bern Cantonal Police, examined the flight path, meteorological data, and radio communications. Investigators reviewed the pilot's training records, which included significant experience on the aircraft type, and confirmed the aircraft was airworthy with no mechanical failures detected.
Radio transcripts revealed that the pilots were in contact with Bern Tower and each other. The investigation also analyzed the weather reports from the time of the accident, which indicated a moving low-pressure system bringing rain and lowering cloud bases. Witnesses on the ground observed the two aircraft flying through the fog near Rekholtern before the collision occurred.