What happened
On February 23, 1964, a pilot operating for Heliswiss was conducting passenger flights near St. Moritz. After noting a low fuel level of approximately eight gallons during a landing, the pilot decided to fly to Samedan Airport to refuel. The flight path included an intermediate stop at Piz Staz, where the aircraft remained on the ground briefly without shutting down the engine.
While approaching Samedan, the engine failed as the fuel pressure warning light activated. The pilot was forced to perform an autorotative landing approximately 500 meters south of runway 03. Due to strong west-southwest winds, the aircraft was unable to turn into the wind and approached the landing site with a near tailwind. In an attempt to reduce forward speed, the pilot maintained a steep attitude during the final phase of the descent. Upon contact with the snow-covered ground, the main rotor blades struck the rear of the fuselage, causing the aircraft to lose directional control and come to a rest after a brief bounce and rotation.
The investigation
The investigation examined the fuel system, the aircraft's maintenance history, and the environmental conditions at the time of the accident. Investigators reviewed the fuel capacity of the Bell 47 G-2, noting that while the tanks held 61 U.S. gallons, approximately four gallons were unusable under certain conditions. The investigation also looked into the pilot's flight experience and the specific mechanics of the rotor strike during the landing.
Findings
- The engine failure was caused by insufficient fuel reserves, as the difference between the fuel indicated and the usable fuel led to starvation.
- The landing was performed under unfavorable conditions, specifically a tailwind component that prevented the pilot from turning into the wind.
- The collision between the rotor blades and the fuselage was caused by the high pitch angle maintained by the pilot to arrest forward momentum during the landing.
- All three occupants (the pilot and two passengers) remained uninjured.
- The Bell 47 G-2, registration HB-XBT, sustained heavy damage to the rotor blades, tail rotor, and rear fuselage.