For the ferry flight, the pilot placed an overnight bag on the passenger seat, leaned a swag and fuel pump against the seat and secured the lot with the seat belt. His pre-flight control checks revealed that full control travel was available for the collective and cyclic controls. During the climb the swag slipped and came to rest against the cylic control. At this stage it was not causing any control interference. The pilot intended to fly past the lee side of a mountain and found that the swag was now restricting movement of the cyclic pitch control. The seat belt was unfastened to reposition the swag. At the same time, the helicopter encountered some turbulence. The swag fell onto the collective pitch control lever, pushing it nearly all the way down. The helicopter descended out of control with both the cyclic and collective controls fouled. The pilot managed to regain partial control just before impact and, following the heavy landing, rolled the helicopter into a steeply sloping rock face. The pilot commented later that the critical point in the scenario was reached when he unlatched the seatbelt to fix an annoying, but not serious problem at an inappropriate time. This accident was not the subject of a formal on scene investigation.