The pilot made an early morning DEPARTURE from the station strip. He reported that as the aircraft accelerated past 65 to 70 knots he selected gear up, however, the gear did not immediately retract and the gear safety override warning activated. The gear then retracted but shortly afterwards he heard a "clanging" noise which he assumed was coming from the engine. He immediately reduced power, selected gear down and turned back towards the strip for a forced landing. The turn was commenced from about 150 to 200 feet above the terrain, but after turning through about 160 degrees the aircraft stalled. The aircraft collided with the ground and after a ground run of approximately 122 metres the left wing struck two trees which yawed it through 180 degrees. The gear collapsed and the aircraft skidded backwards for 32 metres. An examination of the aircraft failed to detect any pre-impact malfunction with the engine or propeller. The source of the "clanging" noise reported by the pilot could not be established, although the post impact damage may have destroyed the evidence of the noise source. There was no other evidence of power loss. The pilot had been working very long hours over the preceding three days and was fatigued. It is possible that the level of fatigue had a deleterious affect on the pilot's ability to rapidly and correctly assess the action required. The pilot mistakenly identified a noise from an unknown source as an engine or propeller malfunction and reduced power by a substantial amount. The pilot then selected gear down and attempted a turn back manoeuvre from only 150 to 200 feet above ground level without increasing power. The aircraft subsequently stalled. The activation of the gear safety override system probably added to the confusion and reinforced in the pilot's mind that the aircraft had a serious malfunction.