What was found
DURING PRE-DEPARTURE CHECK OF AIRCRAFT, A BURNING ODOR WAS DETECTED IN AFT BAGGAGE AREA. UPON CLOSER INSPECTION, SMOKE NOTED COMING FROM BENEATH THE HAT SHELF. POWER WAS REMOVED AND THE NR 2 HG-1075 INERTIAL REFERENCE UNIT WAS REMOVED. THE IRU FAN INVERTER WAS FOUND TO BE THE SOURCE OF THE SMOKE. INSTALLED HONEYWELL DC BLOWER KIT, PN 26012423-105, IN ALL 3 IRU'S AND RETURNED AIRCRAFT TO SERVICE.