What happened
On April 9, 1967, a Bell 47 G helicopter, registration HB-XAV, was engaged in a private flight near Burgdorf, Switzerland. The flight included the pilot, two passengers, and a dog. After an earlier stop for lunch, the pilot identified a field near the village of Belp for a simulated off-airport landing.
At approximately 16:00, the pilot performed a simulated landing, hovering about one meter above the ground. During the attempt to transition into a takeoff, the pilot encountered a drop in engine RPM. In an effort to maintain control, the pilot pulled the cyclic control fully aft. However, the aircraft, which was experiencing a tailwind and gusty conditions, tilted forward. The skids made contact with the soft edge of the field, causing the helicopter to pitch forward and strike the ground with its rotor blades. The impact resulted in the total destruction of the aircraft.
The investigation
The investigation examined the aircraft's technical condition, the pilot's experience, and the environmental factors present at the time of the accident. Investigators reviewed the pilot's training records, noting he was undergoing advanced training and had recently completed his helicopter rating. The investigation also analyzed the aircraft's weight and balance, as well as the meteorological conditions, which included a Föhn wind event characterized by gusty conditions.
Findings
- The aircraft's center of gravity was outside the permissible limits, specifically positioned too far forward, making the helicopter nose-heavy.
- The pilot attempted a takeoff into a tailwind during a period of gusty winds, which negatively impacted the maneuver.
- The combination of the improper weight distribution and the unfavorable wind conditions caused the pilot to lose control of the aircraft.
- The pilot had not obtained permission from the landowner or the tenant for the off-airport landing.