What happened
On December 30, 1999, an Alouette III SA 316B, registration HB-XXC, was performing a commercial flight near Reichenbach, Switzerland. The mission was part of a wedding surprise, intended to transport passengers from Reichenbach to Mürren. During the final approach to a designated landing zone near a riding hall, the pilot initiated a right-hand turn to align with the landing area.
As the aircraft descended toward the site, it struck overhead electrical cables. The impact caused the cables to wrap around the rotor mast and strike the landing gear, resulting in a sudden loss of control. The helicopter was thrown tail-first into the ground from a low altitude. The collision resulted in two serious injuries among the passengers, while the pilot escaped the wreckage without injury. The aircraft was a total loss, and the power lines were damaged.
The investigation
Investigators examined the flight circumstances, the aircraft's maintenance records, and the landing site conditions. The investigation established that the landing zone had been changed shortly before the flight, moving from the original plan to a location between a road and the Kander river. The pilot received the mission details late on the morning of the accident, leaving insufficient time for a ground reconnaissance of the new site.
Technical inspections confirmed that HB-XXC was airworthy, with all weight and balance parameters within limits and no pre-existing mechanical defects. The investigation also noted that the electrical lines, while not required to be on aeronautical charts due to their size, were difficult to see due to the low sun angle and diffuse lighting conditions during the approach.
Findings
- The primary cause of the accident was an inadequate flight tactic during the approach to a difficult landing zone.
- The pilot focused exclusively on the marked landing area, failing to maintain adequate scanning of the surrounding environment.
- There was a lack of ground reconnaissance by both the pilot and the flight operations management prior to the flight.
- The pilot's flight experience and training level were insufficient for the complexities of the specific landing site.
- The landing zone was inherently unsuitable due to the surrounding obstacles and tight maneuvering space.