Accident Overview
On 28 September 1984 at 1325 local time, a SA 315B "Lama" helicopter, registration HB-XII, operated by Air Zermatt AG, was involved in an accident at Tätschen, approximately 5 km north of Brig, Switzerland, at an elevation of 1780 m. The helicopter was engaged in commercial external load transport and was destroyed in the accident.
Flight History
The pilot had been conducting external load transport flights. After setting down a material container on a parking area, the pilot, believing the load had been released and intending to land the helicopter next to it, initiated a lateral shift to the right without checking the release device's indicator light. Upon realizing the load was still attached, he activated both the mechanical and electrical release mechanisms, but the separation occurred too late. The helicopter tipped onto its right side, and the rotor struck the ground. The pilot evacuated the helicopter uninjured.
Findings
- The pilot held a valid professional helicopter pilot license.
- The helicopter was airworthy and certified for operations.
- Weight and center of gravity were within permissible limits.
- The electrical release mechanism and its indicator light were tested with loads up to 600 kg and supply voltages between 20-28 V, with no pre-existing defects found. The manufacturer specifies a minimum load of 6 kg for reliable release.
- The pilot stated that he did not check the release mechanism's indicator light before initiating the lateral flight.
- At the accident site, the load was found separated on the ground.
Probable Cause
The accident was caused by the pilot forgetting to activate the release mechanism after setting down the load. Contributing factors were an inadequate flight maneuver and insufficient monitoring of the release process.