Incident Overview
On 6 January 2002 at 1630 local time, a helicopter SA 315 B Lama, registered as HB-XPP, operated by Heliswiss, was conducting commercial external load operations in Adelboden, Canton Bern, Switzerland. The aircraft was in a hover at an altitude of 1290 m AMSL, preparing to transport a disassembled video tower. The external load capacity was within limits, and the pilot held a valid commercial license with approximately 8300 total flight hours.
Sequence of Events
The accident occurred following the final ski race of a FIS event. A 9-meter-long steel beam (approximately 650 kg) used to support a video wall was being prepared for aerial transport. Two ground workers attached textile loop straps to both ends of the beam. The designated flight coordinator instructed the pilot to pick up the load. The pilot lowered a 14-meter line with a swivel hook; one worker opened the safety latch and hung both straps onto the hook. After a brief adjustment, the helicopter slowly lifted the load. The beam initially hung horizontally, but as the helicopter shifted sideways, one strap detached from the hook. The beam, now supported only on one side, slipped out of the remaining strap and fell vertically to the ground. It struck a television employee who was coiling transmission cables near the base of the scaffold.
Technical Findings
Investigation revealed that the steel beam was a double T-profile with four trolleys for the video wall. The two textile straps were 6 m long, 6 cm wide, with a strength of 2000 kg each. The hook system included a 12 m steel cable, a 6 m hemp rope damping element, and a swivel hook with a spring-loaded safety latch. No pre-existing defects were found in the lifting equipment. The geometry of the strap triangle showed a spread angle of approximately 102° and a slope angle of 51°, resulting in a 60% increase in tension per strap. The wide spread angle caused one strap to bear against the safety latch upon lift-off. The latch, designed only for securing the load in an unloaded state, was forced open, releasing the strap. The report noted that for such wide angles, an intermediate link (e.g., a shackle) is required between the straps and the hook.
Injuries
The TV employee suffered serious head, shoulder, back, and leg injuries. He had entered the danger zone unnoticed by the flight coordinator or pilot. He later experienced retrograde amnesia and could not recall the event. No other persons were injured, and neither the helicopter nor third-party property sustained damage.
Conclusion
The accident was attributed to the inadequate attachment of the external load to the swivel hook. The absence of an intermediate link between the textile straps and the hook allowed one strap to press against the safety latch, which failed under load.