Narrative:

The aircraft was released per the MEL with the APU dual bleed light inoperative. While preflting the aircraft the APU fire detector inoperative light illuminated and a short sounding of the fire bell explained the automatic shutdown of the APU. I had a mechanic (called in from home) close APU air delivery valve and verify its closure by touching the ducts before and aft of the valve confirming no leaks of hot air. We were now re-released with APU dual bleed light inoperative. APU fire detector inoperative, and APU inoperative. On takeoff from pud climbing through 500' we got a fire warning (bell and light in handle). Although I knew the fire warning was erroneous and the fire warning system MEL'd, T 500' is not time to analyze. I followed procedure by pulling the fire handle and firing the extinguisher. I leveled off at 3000' and circled back toward the approach end of runway. The red fire light never went out and testing the fire system revealed an erroneous indication by its flickering (statically). I called company to advise and they requested I take aircraft to bos for maintenance and passenger accommodations. Because the APU had been thoroughly secured and because the fire detection system was MEL'd as inoperative, I followed the company's request and diverted to bos. The only additional action (which should be made part of the MEL process) is to pull and secure the circuit breaker to the fire detection system. This pulling the circuit breaker is in fact all that was done before we departed bos (after an inspection). Supplemental information from acn 142374: the captain then stated that the company wanted us to go to bos for maintenance and passenger accommodation. I told the captain that I did not feel that was an option, and we only had 2--to either ignore the light (since the system was inoperative), or to land at pvd. He chose to go to bos, so we diverted to bos because he felt that everything was secure and wanted to do what the company asked. We asked for priority handling into bos, because the APU fire warning light and the APU fire detector inoperative light began flashing alternately and the fire bell kept cycling off and on. We received priority into bos and landed west/O incident.

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Original NASA ASRS Text

Title: APU FIRE WARNING.

Narrative: THE ACFT WAS RELEASED PER THE MEL WITH THE APU DUAL BLEED LIGHT INOP. WHILE PREFLTING THE ACFT THE APU FIRE DETECTOR INOP LIGHT ILLUMINATED AND A SHORT SOUNDING OF THE FIRE BELL EXPLAINED THE AUTO SHUTDOWN OF THE APU. I HAD A MECH (CALLED IN FROM HOME) CLOSE APU AIR DELIVERY VALVE AND VERIFY ITS CLOSURE BY TOUCHING THE DUCTS BEFORE AND AFT OF THE VALVE CONFIRMING NO LEAKS OF HOT AIR. WE WERE NOW RE-RELEASED WITH APU DUAL BLEED LIGHT INOP. APU FIRE DETECTOR INOP, AND APU INOP. ON TKOF FROM PUD CLBING THROUGH 500' WE GOT A FIRE WARNING (BELL AND LIGHT IN HANDLE). ALTHOUGH I KNEW THE FIRE WARNING WAS ERRONEOUS AND THE FIRE WARNING SYS MEL'D, T 500' IS NOT TIME TO ANALYZE. I FOLLOWED PROC BY PULLING THE FIRE HANDLE AND FIRING THE EXTINGUISHER. I LEVELED OFF AT 3000' AND CIRCLED BACK TOWARD THE APCH END OF RWY. THE RED FIRE LIGHT NEVER WENT OUT AND TESTING THE FIRE SYS REVEALED AN ERRONEOUS INDICATION BY ITS FLICKERING (STATICALLY). I CALLED COMPANY TO ADVISE AND THEY REQUESTED I TAKE ACFT TO BOS FOR MAINT AND PAX ACCOMMODATIONS. BECAUSE THE APU HAD BEEN THOROUGHLY SECURED AND BECAUSE THE FIRE DETECTION SYS WAS MEL'D AS INOP, I FOLLOWED THE COMPANY'S REQUEST AND DIVERTED TO BOS. THE ONLY ADDITIONAL ACTION (WHICH SHOULD BE MADE PART OF THE MEL PROCESS) IS TO PULL AND SECURE THE CB TO THE FIRE DETECTION SYS. THIS PULLING THE CB IS IN FACT ALL THAT WAS DONE BEFORE WE DEPARTED BOS (AFTER AN INSPECTION). SUPPLEMENTAL INFO FROM ACN 142374: THE CAPT THEN STATED THAT THE COMPANY WANTED US TO GO TO BOS FOR MAINT AND PAX ACCOMMODATION. I TOLD THE CAPT THAT I DID NOT FEEL THAT WAS AN OPTION, AND WE ONLY HAD 2--TO EITHER IGNORE THE LIGHT (SINCE THE SYS WAS INOP), OR TO LAND AT PVD. HE CHOSE TO GO TO BOS, SO WE DIVERTED TO BOS BECAUSE HE FELT THAT EVERYTHING WAS SECURE AND WANTED TO DO WHAT THE COMPANY ASKED. WE ASKED FOR PRIORITY HANDLING INTO BOS, BECAUSE THE APU FIRE WARNING LIGHT AND THE APU FIRE DETECTOR INOP LIGHT BEGAN FLASHING ALTERNATELY AND THE FIRE BELL KEPT CYCLING OFF AND ON. WE RECEIVED PRIORITY INTO BOS AND LANDED W/O INCIDENT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.