What was found
WITH BATTERY IN OVERRIDE, APU DOOR OPEN, APU NOT RUNNING, NOTICED WHITE SMOKE FOLLOWED BY FLAMES COMING OUT OF THE TAILPIPE. APU FIRE BOTTLE WAS DISCHARGED, DID NOT EXTINGUISH FLAMES. FIRE DEPARTMENT EXTINGUISH FLAMES. NO FIRE WARNING IN COCKPIT AT ANY TIME. PERFORMED APU FIRE INSPECTION IAW 5-50-00. INSPECTED APU COMPARTMENT & APU EXHAUST AREAS, DISCOVERED NO VISIBLE SIGNS OF ANY OF FIRE. REMOVED AND REPLACED LT & RT FIRE BOTTLES & CARTRIDGES IAW CMP CODE 262003. REMOVED AND REPLACED THE APU. OPS & LEAK CHECKED GOOD. IAW MM 53-35-00, 49-00-00 & 49-10-00.