As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT APPROXIMATELY LEVEL OFF AT FLIGHT LEVEL 280, APU FIRE WARNING LIGHT AND HORN SOUNDED. APU FIRE CHECK, LIST ACCOMPLISHED IAW AIRCRAFT OPERATION MANUAL PROCEDURES. FIRE BOTTLE DISCHARGED. APU FAILED TO SHUT DOWN AND WAS RUNNING IN FLIGHT, CAUSING AN OVER TEMPERATURE CONDITION. REMOVED AND REPLACED THE FUEL SHUTOFF VALVE AND 3-SPEED SWITCH. (M)