What was found
CLIMBING THROUGH 5,000 MSL, FLIGHT CREW REPORTED APU FIRE INDICATION. AN EMERGENCY WAS DECLARED AND AIRCRAFT RETURNED TO IAH AND LANDED WITHOUT INCIDENT. REPLACED APU FIRE BOTTLE PER MM 26-22-11, PAGE 401-406. PLACARDED APU AND APU FIRE DETECTION SYSTEM PER MEL 26-8A. COMPLIED WITH SP 26-8. NO EVIDENCE OF FIRE WAS FOUND. AN ADDENDUM TO THIS SDR WILL BE SUBMITTED UPON REMOVAL OF THE PLACARD. ADDENDUM: ON 4/9/04, REPLACED BOTH APU EXHAUST FIRE DETECTOR ELEMENTS PER MM 26-15-14, PERFORMED OPERATIONAL CHECK AND CHECKED OKAY. REPLACED EXHAUST OVERHEAT ELEMENT, P/N 896768, S/N 217. REPLACED EXHAUST FIRE ELEMENT, P/N 896767, S/N 2178.