NTSB Probable Cause

FAILURE OF THE PILOT TO MAINTAIN AIRCRAFT CONTROL DUE TO SPATIAL DISORIENTATION, AND HIS EXCEEDING THE DESIGN STRESS LIMITS OF THE AIRCRAFT, WHICH RESULTED IN OVERLOAD FAILURE OF THE STABILATORS AND WINGS. FACTORS RELATED TO THE ACCIDENT WERE: THE PILOT'S FAILURE TO FOLLOW PROCEDURES/DIRECTIVES, HIS LACK OF RECENT INSTRUMENT EXPERIENCE, EXCESSIVE GROSS WEIGHT OF THE AIRCRAFT ALLOWED BY THE PILOT, DARK NIGHT, AND ADVERSE WEATHER CONDITIONS.