On the day before the accident, the pilot had been mustering cattle on Cukadoo Station which is the neighbouring property to Nithsdale. The owner of Cukadoo had accompanied the pilot during the mustering operation, which was close to the accident site. The pilot had flown over a single-wire powerline several times during the day, and remarked that he would have to be careful of the powerlines. This was a spur line which joined the main line (which the helicopter struck) at right angles, approximately 1.4 km from the accident site. Late in the afternoon the pilot flew to Mt Isa, where he remained overnight, with the intention of returning to his own property in the Northern Territory the next day. During the evening he had telephoned the owner of Mt Ryde Station west of Longreach, where he had cattle on agistment. The cattle were being driven to another property in the Northern Territory recently purchased by the pilot. The pilot was told that some of the cattle were still at Mt Ryde and he became very concerned. The pilot said he would come down to Mt Ryde to resolve the matter. At about 0930 the next morning the sound of a helicopter was heard passing near Cukadoo homestead 200 km southeast of Mt Isa at very low altitude. Initially it appeared that the helicopter was going to land there, but the noise receded towards the southeast without the helicopter being sighted. About 5 minutes later the electricity supply to the homestead failed. Later in the day the wreckage of the helicopter was discovered by linesmen who were investigating the cause of the electrical supply failure. The helicopter had struck the Single Wire Earth Return (SWER) 19 Kilovolt line 9.5 km southeast of Cukadoo homestead. The wire was struck approximately mid-span between supporting poles 400 m apart, and about 7.5 m above ground level. The line was aligned approximately at right angles to the south-easterly flight path of the helicopter. The wire impacted the nose of the helicopter at about floor level, causing the helicopter to pitch nose-down, and the main rotor to sever the tail boom. The helicopter then impacted the ground and burned. Wreckage distribution indicated that the helicopter may have been at cruising speed at the time of impact with the wire. The location of the accident was approximately on track between Mt Isa and Mt Ryde. The powerline was in flat open grassland which could cause the poles to blend with the background. At the time of the accident the weather was fine, but there was a 10 to 15 knot south-easterly wind, and it appears that the pilot may have been flying at low level in an attempt to conserve fuel. There were no mechanical defects discovered which may have led to the development of the accident.