NTSB Probable Cause

VFR FLIGHT BY THE NON-INSTUMENT RATED PILOT INTO INSTRUMENT METEOROLOGICAL CONDITIONS (IMC), HIS LOSS OF AIRCRAFT CONTROL, DUE TO SPATIAL DISORIENTATION, AND HIS EXCEEDING THE DESIGN STRESS LIMITS OF THE AIRCRAFT, WHILE RECOVERING FROM AN UNCONTROLLED DESCENT. FACTORS RELATED TO THE ACCIDENT WERE: DARK NIGHT, ADVERSE WEATHER CONDITIONS, LOSS OF THE VACUUM SYSTEM, AND THE PILOT'S LACK OF INSTRUMENT EXPERIENCE.