The pilot intended to conduct a practice aerobatic flight, and had arranged for an observer on the ground to monitor and assess his performance. The planned sequence was commenced, but the observer noted that the second manoeuvre was not completed satisfactorily, and the aircraft apparently stalled while inverted. After recovering from this situation, further manoeuvres were carried out. Other witnesses suggested that the entries to some of these manoeuvres were performed at higher "G" loadings than normal. The aircraft subsequently entered a spiral dive, which was continued without any apparent effort being made to effect recovery. The aircraft maintained the spiral until it collided with power lines, then impacted the ground. A fierce fire broke out and consumed the wreckage. A detailed investigation failed to discover any defect or malfunction with the aircraft or its systems which might have contributed to the accident. The pilot had been in current practice for aerobatic flight, and there was no evidence of any physical illness or incapacity which might have affected his ability to control the aircraft. However, it was evident that the aircraft was not under control during the spiral dive. It was considered possible that the pilot might have lost consciousness as a result of either a rapid increase in "G", or sustained high "G" loads applied during the preceding aerobatic sequence.
