What happened
On January 4, 1970, a Beagle B-121 Pup, registration HB-NAO, was engaged in a flight originating from Sion. The pilot, accompanied by one passenger, had initially planned a route through the Rhône Valley toward Berne. However, deteriorating weather conditions and heavy turbulence in the valley prompted the pilot to divert to the Bex aerodrome.
During the approach to runway 15, the pilot encountered several complications. The aircraft's radio had ceased functioning, and the pilot was navigating through heavy turbulence and low visibility caused by snow. While attempting the landing, the pilot misidentified a dark, snow-free patch of ground near the threshold as an obstacle and applied additional power. This maneuver, combined with an approach performed at a high speed and with the flaps retracted, caused the aircraft to land approximately 250 meters beyond the runway threshold.
Upon touchdown, the pilot attempted to brake, but the surface of the runway was partially covered in ice and frozen snow. The lack of effective braking, coupled with the high touchdown speed, caused the aircraft to overshoot the airfield boundaries, strike a fence, and descend a slope into a nearby field. The aircraft was destroyed, while the pilot sustained minor injuries and the passenger remained unharmed.
The investigation
The investigation examined the aircraft's mechanical state, the pilot's experience, and the environmental conditions at the time of the accident. Investigators reviewed the aircraft's maintenance records and found no evidence of pre-existing technical failures that would have prevented flight. The investigation also looked into the cause of the radio failure, noting that a potential electrical issue involving the alternator circuit breaker could have led to a voltage drop when the landing light was activated.
Furthermore, the investigation analyzed the runway conditions, noting that the presence of ice significantly reduced the braking coefficient. The investigators also examined the pilot's flight history, noting his relatively limited experience in the aircraft type and general flight hours.