What happened
On October 1, 1963, at 16:10 CEST, an Agusta-Bell 47 G-I was conducting training maneuvers at Bern Airport (Belp) in Switzerland. The pilot was performing his third autorotation landing exercise of the session, approaching parallel to runway 32 from the right.
During the descent, the pilot reduced the airspeed from approximately 40 mph to 10 mph at an altitude of 60 meters. As the aircraft reached roughly 1 meter above the ground, the pilot applied collective pitch to arrest the descent. While attempting to push the cyclic forward to level the aircraft, the helicopter made contact with the ground while still in a slightly nose-high attitude. The rear of the skids struck the terrain first, causing the aircraft to pitch forward abruptly. In a reflexive response to the sudden forward tilt, the pilot pulled the cyclic toward himself, which caused the main rotor to flex downward and strike the tail boom, severing it.
The investigation
The investigation focused on the mechanics of the landing and the pilot's control inputs. The aircraft, operated by Schweizerische Helikopter AG, was well within its weight and balance limits, weighing approximately 800 kg at the time of the incident. The investigator noted that the engine and mechanical components had been functioning perfectly prior to the impact. Meteorological conditions were stable, with overcast skies and light winds.
Findings
- The primary cause of the accident was that the helicopter was not parallel to the ground at the moment of touchdown.
- The landing occurred on the rear edges of the skids, triggering a sudden forward pitch.
- The pilot's instinctive reaction to pull the cyclic back during the pitch-forward motion contributed to the rotor blade deflection that led to the tail boom strike.