What happened
On July 21, 1999, a Schweizer Aircraft Corp. 269C helicopter, registration HB-XZC, was conducting a commercial photography flight near Adelboden, Switzerland. After landing on a hill southwest of Adelboden to seek better lighting for photography, the pilot attempted a takeoff approximately 30 minutes later.
During the initial climb, the pilot maneuvered the aircraft toward a power line at the edge of a ridge. As the pilot accelerated southward along the slope, they realized the aircraft lacked sufficient speed and altitude to clear the terrain and decided to abort the takeoff. While attempting to turn the helicopter back toward the ridge, the aircraft was unable to maintain altitude. The helicopter struck steep terrain, causing the skids to impact the ground. The aircraft subsequently spun down the slope, eventually coming to rest near a farmhouse. The pilot and the photographer escaped without injury, though the Schweizer Aircraft Corp. 269C sustained heavy damage, and a nearby building and agricultural machinery were also damaged.
The investigation
The investigation examined the aircraft's performance capabilities, the pilot's experience, and the environmental conditions at the time of the accident. Investigators found that the helicopter was equipped with a muffler kit, which was not accounted for in the performance calculations provided in the Pilot's Flight Manual (PFM).
Furthermore, the investigation revealed that the HOGE (Hover Out of Ground Effect) and HIGE (Hover In Ground Effect) performance tables published in the PFM were significantly too optimistic. While the manufacturer provided this data as a service, the values were not FAA-certified and did not reflect the actual performance limitations of the aircraft when equipped with additional components like the muffler. The investigation also noted that the pilot had relatively low experience conducting mountain operations in this specific helicopter model.