NTSB Probable Cause

IMPROPER IN-FLIGHT PLANNING/DECISION BY THE PILOT, AND HIS FAILURE TO MAINTAIN ALTITUDE AND CLEARANCE ABOVE THE TERRAIN, WHILE PERFOMING LOW ALTITUDE, INVERTED FLIGHT. FACTORS RELATED TO THE ACCIDENT WERE: THE LACK OF VISUAL PERCEPTION TO THE PILOT AT DUSK (TWILIGHT), THE PILOT'S OVERCONFIDENCE IN HIS PERSONAL ABILITY, AND HIS LACK OF EXPERIENCE IN THIS AIRCRAFT AND TYPE OF OPERATION.