The aircraft was observed to take off normally and climb to about 200 feet above ground level. Shortly after passing beyond the end of the strip, an apparent change in aircraft engine noise was heard by witnesses. The aircraft was then seen in a steep nose-down, inverted attitude. It remained in this attitude until ground impact. On site examination showed that the aircraft had struck the ground in an inverted nose-down attitude of 35 degrees. No fault was found in the aircraft or its systems which might have contributed to the accident. The engine was operating at impact. Witnesses reported that the pilot had complained of chest pains both on the morning of the accident and the previous evening. The post mortem report on the pilot indicated that, if other causes of the accident were excluded, there was sufficient chronic heart disease present for sudden heart failure or sudden death to have been likely events.