NTSB Probable Cause

FAILURE OF THE PILOT TO MAINTAIN CONTROL OF THE AIRCRAFT, WHICH RESULTED IN A SPIN AND AN UNCONTROLLED DESCENT. FACTORS RELATED TO THE ACCIDENT WERE: IMPROPER MAINTENENCE BY THE PILOT, AN AUTOPILOT MALFUNCTION, THE ADVERSE WEATHER CONDITIONS, CONTINUED FLIGHT BY THE PILOT INTO ADVERSE WEATHER CONDITIONS, AND HIS LACK OF RECENT INSTRUMENT EXPERIENCE.