What happened
On February 10, 1975, at approximately 10:30 AM, a flight instructor and a student pilot departed from Mollis airfield. The purpose of the flight was to practice mountain landing techniques at the Planura landing site. During the flight, the crew performed several maneuvers in close proximity to rock faces and low-altitude passes over snow-covered ridges near the Jegerstö and Ortstock regions.
As the aircraft transitioned between the north and south sides of the mountain massif, it entered a series of steep turns. During one of these maneuvers, the aircraft approached a rising rock section too closely. The aircraft subsequently entered a spiral dive, striking a near-vertical rock wall before falling approximately 350 meters down a slope to a snowfield. Both occupants of the Champion 7 GCB, registration HB-UAU, sustained fatal injuries.
The investigation
An investigation by the Swiss authorities examined the flight path, the condition of the aircraft, and the environmental factors at the time of the accident. Witnesses observed the aircraft performing low-level maneuvers near the cliffs, including a sharp turn away from the rock faces and a subsequent return toward them.
Technical examination of the wreckage showed that the aircraft's controls, linkages, and engine components were in good working order, with no evidence of pre-existing mechanical failure. The investigation also reviewed the weight and balance of the aircraft, noting that the total weight was approximately 42 kg above the maximum allowable takeoff weight. The crew's medical examinations and flight licenses were also verified, confirming they were both legally qualified for the flight and physically fit.
Findings
- The aircraft was operating significantly overloaded, exceeding its maximum takeoff weight.
- The pilot performed a maneuver that brought the aircraft too close to an ascending rock formation.
- During the execution of steep turns, the aircraft undershot the minimum required airspeed.
- The lack of distinct terrain features on the snow-covered ground likely made distance estimation difficult for the crew.
- Light turbulence in the mountains may have further complicated the flight stability during the critical maneuver.