What happened
On March 25, 1977, a Cessna 177 B Cardinal, registration HB-CVN, was engaged in a private VFR flight between Gruyères and Ecuvillens. During the flight, the pilot performed a demonstration of engine-out capabilities by descending toward the ground near Riaz. Following this, the pilot identified a field near Gumefens as a suitable landing site. During the approach to this unprepared terrain, the aircraft passed near high-voltage power lines and a farm. The landing was hard, causing the nose gear fork to break and the propeller to strike the ground, creating a furrow. Despite the damage, the pilot managed to take off again and return to Ecuvillens.
Upon returning to Ecuvillens, the pilot did not report any damage to the airfield control. During the landing on runway 10, the aircraft's nose gear—which had been broken during the previous maneuver—failed to support the weight. The aircraft struck the ground, the nose pitched down, and the plane subsequently flipped onto its back approximately 75 meters from the runway threshold. The two occupants sustained only minor contusions and exited the aircraft unaided.
The investigation
The investigation established that the aircraft was airworthy and properly maintained, with no mechanical defects contributing to the accident. However, the pilot's blood alcohol content was estimated between 0.2 and 0.4 ‰ due to consumption earlier that day. The investigation also found that the pilot had twice violated minimum flight altitude regulations during the flight.
Investigators examined the sequence of the two landings, noting that the first landing at Gumefens was a reckless demonstration that caused the structural failure of the nose gear fork and misaligned the engine mount. It was also noted that the pilot failed to notify the airfield of the aircraft's damaged condition, which prevented instructors on-site from suggesting a low-level flyby to inspect the landing gear.