What was found
AIRCRAFT DEPARTED, ENROUTE FIRE WARNING ILLUMINATED. PILOT INITIATED EMERGENCY PROCEDURES, ENGINE WAS SHUTDOWN. ON SHUTDOWN, FIRE WARNING INUCIATOR EXTINGUISHED. A NORMAL RUN ON LANDING WAS COMPLETED WITHOUT INCIDENT. MX INSPECTED ACFT, TESTED MASTER CAUTION, AND RETURNED THE ACFT TO SERVICE, UNABLE TO REPEAT THE DISCREPANCY. ACFT WAS GROUND RUN FOR 10 MINUTES, HOVERED FOR 10 MINUTES AND FLOWN FOR 20 WITHOUT A RECURRENCE.