Circumstances The pilot had arranged to visit the property of a friend in the Kingaroy area. He planned to arrive at the property at about 0900. At 0930, the pilot rang his friend and advised that he would not arrive until 1200-1230. The delay was the result of maintenance needed on the aircraft which required the pilot to fly the aircraft to Caloundra and return to Redcliffe before departing for Kingaroy. The pilot and his passenger arrived at the property at about 1230 where they lunched and spent the afternoon. When it came time to leave, the property owner decided to accompany his friend in his own Lightwing aircraft for part of the return journey. They boarded their respective aircraft and the Lightwing became airborne and waited in the area for about 10 minutes for the Skyfox to become airborne. The pilots eventually gained radio contact with each other but the pilot of the Skyfox gave no reason for his delayed departure. Both aircraft set course for Nanango and the Skyfox, which had been above and behind the Lightwing, overtook the other aircraft and they continued at about 2,000 ft above ground level (AGL). The pilot of the Skyfox then descended his aircraft, followed by the Lightwing, to overfly an old airstrip at an altitude of between 10 ft and 20 ft AGL, before climbing to a reported 2,000 ft AGL. The Skyfox pilot then advised his friend that he was going to overfly another airstrip and descended. The Lightwing remained at altitude. During the descent the pilot of the Lightwing reported seeing a short then continuous stream of whitish smoke from the rear of the aircraft. He attempted to contact the Skyfox pilot by radio but received no response. The aircraft was observed by a ground witness to complete two to three orbits of a property homestead before commencing a flypast over the homestead in a southerly direction. The witness stated that he did not observe any smoke from the aircraft. He then reported hearing the sound of the two powerline wires coming together and then observing the aircraft with the wings level but in a shallow descent continue in a southerly direction and impact a tree. The aircraft immediately caught fire and fell to the ground. The wreckage was completely burnt out. Site details The powerline struck by the aircraft was strung between two poles on the top of ridgelines either side of the homestead. The span between the two poles was 560 m and the wires were estimated to have been in excess of 32 m above the ground at the point of impact. The poles were located in trees of a similar height and would have been difficult to see from the aircraft. The distance from the powerline to the tree struck by the aircraft was approximately 160 m. Aircraft examination The aircraft was extensively damaged by the post-impact fire. At the point of contact with the wires, the tip of one propeller blade and a piece of window perspex had been torn from the aircraft. However, the aircraft appeared to have arrived at the impact point substantially intact. No defects were observed with the airframe that could have contributed to the occurrence. The engine was removed from the aircraft for specialist examination. The examination did not reveal any defects that could have contributed to the accident. The examination of engine accessories was hampered by the intensity of the fire. Smoke The opinion of those experienced in the operation and maintenance of similar aircraft indicates that the most likely source of whitish smoke was a leak of engine coolant. The coolant is used to cool the heads of the four cylinders of the engine and a loss of coolant would result in an increase in cylinder head temperature, but would not necessitate an immediate landing. The inspection of the engine did not indicate any signs of a loss of coolant but the fire damage precluded any determination of the serviceability of the coolant system. Pilot aspects The pilot had visited the adjoining property, which is located to the east of the accident site, on the day prior to the accident. Both properties were owned by relatives of the passenger in the aircraft. While visiting the property he had discussed with the owner the upgrading of an airstrip, which was currently used in the operation of model aircraft, to a standard suitable for the operation of the Skyfox. Included in the discussion was a briefing by the property owner to the pilot of the wires surrounding the model airstrip. The briefing did not include the existence of the wires struck by the aircraft on the following day. The property owner was expecting the pilot to overfly his property on the morning of the accident. However, the owner of the property on which the accident occurred was unaware who the occupants of the aircraft were until some hours after the accident. There was no airstrip in the area in which the aircraft was operating prior to its impact with the wires. The wires crossed a ploughed paddock which was unsuitable for the operation of an aircraft. Analysis It could not be positively determined if there was any fault with the aircraft prior to it striking the wires. Likewise, the purpose of the orbits of the homestead near the accident site is unknown. It is also unknown if the pilot had been previously aware of the existence of the wires struck by the aircraft but forgot about them on this occasion. Regardless, it appears that the pilot did not see the wires in time to avoid the collision. Significant factors 1. It could not be determined if the pilot was previously aware of the existence of the powerline struck by the aircraft. 2. The pilot did not see the powerline in sufficient time to avoid the collision. 3. The serviceability state of the aircraft prior to the accident could not be positively determined.