THE ACFT WAS A BEECH TC-45J THAT HAD BEEN MODIFIED INTO A HAMILTON TURBOLINER UNDER STC SA-1821-WE. DURING ARRIVAL, THE PLT REPORTED THAT HE ENCOUNTERED MODERATE ICING AT 4000 FT. HE MADE A LOCALIZER-ONLY APCH TO RWY 35. AN ATC SPECIALIST STATED THAT THEY SAW THE ACFT BREAK OUT OF THE CLOUDS OVER THE APCH END OF THE RWY. AT ABOUT THAT TIME, THE PLT TRANSMITTED THAT HE WAS GOING TO ENTER A LEFT BASE TURN FOR RWY 35 & THAT HE HAD THE RWY IN SIGHT. HE STARTED A TURN, AND SHORTLY THEREAFTER, THE ACFT ENTER A STEEP NOSE DOWN ATTITUDE. THE ACFT IMPACTED IN A RAILROAD YARD IN A RELATIVELY LEVEL ATTITUDE WITH THE LANDING GEAR EXTENDED & THE WING FLAPS RETRACTED. HOWEVER, DURING IMPACT, IT WAS STILL DESCENDING AT A STEEP ANGLE (ESTIMATED APRX 30 DEG). IT WAS DESTROYED BY IMPACT & GROUND FIRE. NO PREIMPACT, MECHANICAL FAILURE OR MALFUNCTION WAS FOUND. THE MINIMUM CEILING & VISIBILITY FOR A STRAIGHT-IN APCH WERE 500 FT & 1 MI, AND FOR A CIRCLING APCH, THE MINIMUMS WERE 700 FT & 1 MI.