The aircraft departed Camden on the previous afternoon for a ferry flight to the Kununurra area, with an overnight stop near Eildon, Victoria. About 35 kilometres from Mildura the pilot reported that he was landing due to a vibration. After inspecting the aircraft he continued with the flight but later made a brief Mayday call. Witnesses reported that the engine was running intermittently before the helicopter landed heavily, tail-down, in a vineyard. A contaminant, sufficient in quantity to restrict the flow of fuel, was found in the fuel system filter. The source of the contaminant could not be identified, however an identical polyester material was found in the fuel filter of another new helicopter of the same type. It is probable that the material was present prior to the import of the helicopters. The fuel filters were not inspected prior to the first flight. The helicopter was being operated on super motor spirit at the time but it is considered unlikely, in this instance, to have been the major factor in the engine failure. Due to the pilot's incorrect diagnosis that the power surges were associated with a main rotor problem, he progressively opened the throttle in an attempt to maintain rotor rpm. This action combined with the momentary power surges, exacerbated control difficulties being experienced and resulted in a belated autorotative landing.