WHILE PROCEEDING ON AN IFR FLT PLAN, THE PLT REQUESTED HE BE ASSIGNED AN ALT BELOW 8000 FT DUE TO 'A PASSENGER WITH AN EAR PROBLEM.' OTHERWISE, THE EN ROUTE PORTION OF THE FLT PROCEEDED WITHOUT INCIDENT. DURING ARRIVAL, THE PLT WAS CLEARED FOR AN ILS APCH TO RWY 3. HIS LAST TRANSMISSION WAS MADE AT 1019:45 EST WHEN HE REPORTED INBOUND ON THE AZALEA NDB, WHICH WAS 7.8 MI FROM THE RWY ON THE ILS LOCALIZER. SHORTLY AFTER THAT THE ACFT CRASHED 1.5 MI NW OF THE NBD. AN INVESTIGATION REVEALED THE PLT HAD A HEAD COLD, 2 DAYS EARLIER, & HAD TAKEN MEDICATION, BUT A TOX CHECK (LIVER SAMPLE) SHOWED ONLY 1.8 MG/KG OF CHLORPHENIRAMINE. RADAR DATA SHOWED THAT WHEN THE ACFT WAS NEAR THE NDB, IT MADE SHARP L & R TURNS & HAD DESCENDED FROM 3000 TO 2300 FT BEFORE RADAR CONTACT WAS LOST. THE R WING HAD SEPARATED & WAS FOUND 360 FT FROM THE MAIN WRECKAGE. AN EXAM OF THE V-TAIL SHOWED DEFORMATION OF THE L STAB & UPWARD DEFORMATION OF THE R STAB. NO PRE-ACCIDENT MECHANICAL PROBLEM WAS FOUND. CG ESTIMATED 2.1 INCHES BEHIND AFT LIMIT. PLT DEMO, NO USEFUL VISION, L EYE.