What happened
On June 18, 1964, a Bell 47 G-2 helicopter, registration HB-XAT, was performing a cargo and passenger transport mission near Grindelwald, Switzerland. The pilot, operating for Heliswiss A.G., departed from Bern and arrived at an improvised landing site in Unterer Lauchbühl at approximately 10:35 AM.
Upon arrival, the ground crew intended to assist with loading, but because they had not yet arrived, the pilot decided to load the cargo himself to maintain the schedule. After completing the loading process, the pilot initiated a vertical takeoff, reaching an altitude of approximately one meter. As the aircraft transitioned into forward flight by turning 90 degrees to the left, it struck a steel cable stretched between the ground and a nearby low-roofed building. The impact shattered the Plexiglas cockpit canopy. The pilot managed to increase translational speed, which caused the cable to snap, and successfully landed the aircraft on a nearby ridge about 40 meters away.
The investigation
The investigation focused on the circumstances surrounding the collision and the pilot's actions during the loading phase. Investigators examined the flight path, the visibility conditions, and the presence of the obstacle. The inquiry noted that the pilot was a relatively new helicopter pilot for the operator, having recently completed various training courses including mountain flying. The investigation also reviewed the loading process, noting that the pilot had taken on the responsibility of loading the aircraft personally because the ground support team was delayed.
Findings
- The steel cable, approximately 1 cm in diameter, was positioned only about 15 meters from the takeoff point and was difficult to detect from the air because it lacked a visible mast or support structure.
- The pilot's attention was diverted from essential safety checks due to the task of loading the cargo himself.
- The pilot failed to sufficiently inspect the immediate surroundings for obstacles before commencing the flight.
- The collision resulted in significant damage to the Bell 47 G-2, including irreparable damage to both main rotor blades, a shattered canopy, and damage to the control linkages.