Aircraft and Crew
The helicopter was a SA 315B Lama, registration HB-XPJ, owned and operated by Rhein Helikopter AG of Balzers, Liechtenstein. The pilot held a valid commercial helicopter license and was authorized for external load operations, with 4,128 total flight hours.
Accident Sequence
On 11 October 1990 at about 1600 local time, the pilot was conducting external load transport of windfallen timber near Alp Cholschlag in Mels, Canton of St. Gallen. Two ground teams were present: Group 1 (three forest workers and flight assistant X) prepared the loads, and flight assistant Y attached them to the helicopter's cargo hook.
For the accident flight, assistant Y attached a load prepared by assistant X. The load consisted of four fir logs about 5 m long and 22 cm average diameter, bundled with a single steel sling, plus two larger logs each attached individually. The total weight was at least 900 kg.
After attachment, the pilot lifted the load vertically through the trees while monitoring via an external load mirror. As he transitioned to forward flight, one log from the four-log bundle slipped out of its sling and fell into the forest. The pilot noticed the loss and inquired by radio. While depositing the remaining logs at the landing site, he was informed that flight assistant X had suffered a serious head injury from the falling log.
The pilot immediately transported the injured assistant to the hospital in Walenstadt and then returned to base in Balzers. The helicopter was undamaged.
Findings
- The pilot had a valid license and was qualified; no health issues were detected during the flight.
- The helicopter was properly maintained and had no technical malfunctions contributing to the accident.
- The load attachment equipment (sling and hooks) was in good condition.
- The log that fell was 5.1 m long, 22 cm mid-diameter, weighing about 170 kg.
- The total load weight could not be precisely verified because the remaining logs were not separated at the landing site, but it was at least 900 kg based on pilot indication and estimates.
- Flight assistants X and Y had good to very good knowledge of timber transport operations.
- Assistant X was not wearing a helmet, although employer policy required head protection and helmets were provided. Assistant Y wore a helmet.
- The assistant suffered a serious head injury on the top of the head; the report states with certainty that the severity could have been reduced by wearing a helmet.
- The accident location was about 45 m from the load pickup site; the pickup area was roughly 100 by 300 m.
- Several meters below the pickup site, a construction company was building a new forest road.
Cause
The accident was due to inadequate preparation and attachment of the external load.
Contributing Factors
- Presence of ground personnel below the flight path.
- Flight assistant not wearing a protective helmet.
Recommendations
The Swiss Accident Investigation Board recommended examining whether flight data recorders (FDR) should be required in helicopters conducting commercial external load operations.