The pilot had intended to go fish spotting in his aircraft. At about 1730 hours the aircraft was observed flying at about 100 feet above ground level and heading towards Streaky Bay. No further sightings of the aircraft were reported and when the pilot failed to return home a search was commenced. The wreckage was subsequently located the following morning. The aircraft had impacted in light mulga scrub in a steep nose down attitude. Investigation revealed that the main body tube had suffered an in-flight failure due to metal fatigue. The point of failure was at a junction of the rear engine pylon brace and the body-tube. The fatigue cracking initiated at rivet holes on the upper surface of the body-tube, beneath a doubler in an area which could not be visually inspected. The manufacturer had identified this problem and issued a mandatory inspection directive for this part, but the subject aircraft had not been inspected. Although the pilot was advised of this requirement by a friend, it is unlikely that he received any formal notification of it from the manufacturers local agent.