What was found
ANNUAL INSPECTION DISCOVERED WIDESPREAD CORROSION OF 4130 STEEL FUSELAGE STRUCTURE. LOWER DOOR POST TUBES WERE CORRODED NEARLY THROUGH, RENDERING AIRPLANE UNAIRWORTHY. SIGNIFICANT PORTIONS OF APPARENT ORIGINAL YELLOW FIBERGLASS INSTALLATION WERE WET. AIRCRAFT WAS KEPT OUTSIDE. MOISTURE MIGHT HAVE ENTERED THROUGH WING ROOT, WITH PROBLEM POSSIBLY COMPOUNDED BY HEADLINER BEING FACTORY SALINE-IMPREGNATED (FOR FIRE RESISTANCE), AND BY WICKING OF MOISTURE BY FIBERGLASS INSULATION. THE MOST SIGNIFICANT CORROSION WAS NOT VISIBLE WITHOUT TEARING OUT INTERIOR THAT IS NOT TYPICALLY AND CONVENIENTLY REMOVABLE. AC HAD BEEN FLOATPLANE, SEASONALLY, SINCE 1999.