The pilot had been in the habit of flying about twice per month for a number of years. Each flight was about 30 minutes long and usually involved aerobatic flying. On this occasion the aircraft was observed conducting loops and a barrel roll in the normal area above 3000 feet above sea level. The aircraft later joined the circuit for a landing. While on the crosswind leg the aircraft continued to descend until, at about 700 feet above ground level, the aircraft entered a gentle left turn. The nose dropped during the turn until the aircraft was descending at an angle of about 45`. When the aircraft was about 100 feet above the river the angle increased to about 85` nose down. No changes in engine power were heard during this time. The aircraft struck the Clarence River about 40 metres from the shore at an estimated speed of 180 knots. No evidence of pre-existing defects in the control circuits was found, however, the wings had been torn off on impact and large sections of the control circuits were not recovered. Witnesses reported that nothing was observed to fall off the aircraft and no part of the aircraft was flapping during the descent. Pathological examination concluded that the pilot had died as a result of myocardial ischaemia (lack of blood supply to the heart). The pilot had been hospitalised some years earlier due to a heart attack. This had not been reported to the medical examiner during subsequent licence medical examinations. Hence, as the required tests had not been conducted during licence renewal, it was not possible to determine whether the pilot may have been able to hold a licence at the time of the accident.