NTSB Probable Cause

IMPROPER IFR PROCEDURE BY THE PILOT, AND HIS FAILURE TO MAINTAIN THE MINIMUM DESCENT ALTITUDE (MDA) FOR THAT SEGMENT OF THE VOR APPROACH. FACTORS RELATED TO THE ACCIDENT WERE: DARKNESS, LOW CEILING, FOG, HAZE, THE PILOT'S LACK OF RECENT INSTRUMENT EXPERIENCE, AND HIS PROBABLE SPATIAL DISORIENTATION.