Accident Overview
On 20 July 2006, at approximately 08:45 local time, an AS350B3 Ecureuil helicopter, registration HB-ZDY, sustained tail rotor damage after colliding with a parking fence post during landing at Morteratsch, approximately 5 km east of St. Moritz, Switzerland. The helicopter was operated by Heli Bernina AG. The pilot, a Swiss professional helicopter pilot born in 1968, and one passenger on board were uninjured. The tail rotor blades and their attachment required replacement, and the fence post was also damaged.
Sequence of Events
The pilot had been working for Heli Bernina since 16 July under a reciprocal pilot exchange agreement with Heli Linth. On the day of the accident, the pilot departed Samedan at 08:09 h. After several flights, a flight assistant attached a transport net with a 10-meter extension to the helicopter near the Bovalhütte. The pilot transported the net to the Morteratsch parking area where another flight assistant was waiting. After depositing the net on a gravel path parallel to a river embankment, the pilot prepared to land. The original landing zone on the parking lot was occupied by vehicles, so the pilot and flight assistant agreed to land perpendicularly on the gravel path. During the hover, the flight assistant noticed the helicopter's longitudinal axis was at a 45° angle to the path and radioed “Heck nach rechts” (tail to the right). The flight assistant intended the rotation relative to their own right, but the pilot interpreted the command relative to his own right. As the pilot initiated the final landing phase, he rotated the tail to his right (counterclockwise), causing the tail rotor to strike a parking fence post. After feeling vibrations from the tail rotor, the pilot moved the helicopter slightly forward and landed on the path.
Aircraft Information
The helicopter was an AS350B3 Ecureuil, serial number 3570, built in 2002. It was powered by a Turbomeca Arriel 2B engine. The airframe had accumulated 2469:03 hours at the time of the accident. The mass and center of gravity were within prescribed limits. The last 50-hour inspection was performed on 14 July 2006.
Meteorological Conditions
At the accident site, weather conditions were clear skies, visibility around 20 km, wind variable at 1-2 knots, temperature 10°C, and dew point 8°C. The sun azimuth was 89° with an elevation of 28°. No hazards were identified. Weather did not play a role in the accident.
Conclusions
The accident resulted from the tail rotor colliding with a parking fence post during landing, caused by a misunderstanding between the flight assistant and the pilot regarding the direction of the tail rotation command.