Narrative:

We were dispatched from narita to honolulu with the #1 engine 'B' loop fire detector placarded inoperative and 'a' loop normal. After approximately 3 hours, the #1 engine fire warning light illuminated momentarily, then went out. The 'a' loop nacelle temperature indication was 8.5 plus .3 (fluctuating). The #1 thrust lever was retarded with no decrease in indication. All other engine indications were normal for cruise flight. After approximately 1 min, the fire light illuminated again with the nacelle indicator showing greater than 9.0 and the engine fire checklist was started. ZHN was advised of the problem and of the fact that we would be diverting to wake island and we would be unable to maintain our assigned altitude of 35000 ft because of the loss of an engine and that we were declaring an emergency. As we proceeded with the fire checklist, we discharged the left fire bottle. The left bottle discharge light did not come on. We attempted to discharge the right fire bottle and again there was no indication that the fire bottle discharged. The circuit breakers were checked and found to be normal. We pulled and reset them, and went through the procedures again with no indication again that the fire bottles discharged. The red fire light never did go out. A visual check of the engine showed no indication of a fire. On landing at wake island with the fire light still on, the engine was inspected by the fire crew and found that no fire existed. Further inspection of the engine by maintenance personnel found an opening in the 'a' loop. They also reported that the fire bottles did discharge but did not know why there was no indication in the cockpit. After looking back on this flight, I felt that being dispatched with a bad fire loop on an extended overwater flight can set off a chain of events if the other loop now fails and you end up getting a false fire warning. You must now handle it as if a real fire exists. I feel there is a definite reason for a dual fire detection system. You should be dispatched with the dual system fully operative. I also feel that reducing certain air fields to only an emergency status is definitely reducing our choices of suitable fields.

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Original NASA ASRS Text

Title: AN ACR WDB DIVERTED TO WAK WITH A FALSE FIRE WARNING.

Narrative: WE WERE DISPATCHED FROM NARITA TO HONOLULU WITH THE #1 ENG 'B' LOOP FIRE DETECTOR PLACARDED INOP AND 'A' LOOP NORMAL. AFTER APPROX 3 HRS, THE #1 ENG FIRE WARNING LIGHT ILLUMINATED MOMENTARILY, THEN WENT OUT. THE 'A' LOOP NACELLE TEMP INDICATION WAS 8.5 PLUS .3 (FLUCTUATING). THE #1 THRUST LEVER WAS RETARDED WITH NO DECREASE IN INDICATION. ALL OTHER ENG INDICATIONS WERE NORMAL FOR CRUISE FLT. AFTER APPROX 1 MIN, THE FIRE LIGHT ILLUMINATED AGAIN WITH THE NACELLE INDICATOR SHOWING GREATER THAN 9.0 AND THE ENG FIRE CHKLIST WAS STARTED. ZHN WAS ADVISED OF THE PROB AND OF THE FACT THAT WE WOULD BE DIVERTING TO WAKE ISLAND AND WE WOULD BE UNABLE TO MAINTAIN OUR ASSIGNED ALT OF 35000 FT BECAUSE OF THE LOSS OF AN ENG AND THAT WE WERE DECLARING AN EMER. AS WE PROCEEDED WITH THE FIRE CHKLIST, WE DISCHARGED THE L FIRE BOTTLE. THE L BOTTLE DISCHARGE LIGHT DID NOT COME ON. WE ATTEMPTED TO DISCHARGE THE R FIRE BOTTLE AND AGAIN THERE WAS NO INDICATION THAT THE FIRE BOTTLE DISCHARGED. THE CIRCUIT BREAKERS WERE CHKED AND FOUND TO BE NORMAL. WE PULLED AND RESET THEM, AND WENT THROUGH THE PROCS AGAIN WITH NO INDICATION AGAIN THAT THE FIRE BOTTLES DISCHARGED. THE RED FIRE LIGHT NEVER DID GO OUT. A VISUAL CHK OF THE ENG SHOWED NO INDICATION OF A FIRE. ON LNDG AT WAKE ISLAND WITH THE FIRE LIGHT STILL ON, THE ENG WAS INSPECTED BY THE FIRE CREW AND FOUND THAT NO FIRE EXISTED. FURTHER INSPECTION OF THE ENG BY MAINT PERSONNEL FOUND AN OPENING IN THE 'A' LOOP. THEY ALSO RPTED THAT THE FIRE BOTTLES DID DISCHARGE BUT DID NOT KNOW WHY THERE WAS NO INDICATION IN THE COCKPIT. AFTER LOOKING BACK ON THIS FLT, I FELT THAT BEING DISPATCHED WITH A BAD FIRE LOOP ON AN EXTENDED OVERWATER FLT CAN SET OFF A CHAIN OF EVENTS IF THE OTHER LOOP NOW FAILS AND YOU END UP GETTING A FALSE FIRE WARNING. YOU MUST NOW HANDLE IT AS IF A REAL FIRE EXISTS. I FEEL THERE IS A DEFINITE REASON FOR A DUAL FIRE DETECTION SYS. YOU SHOULD BE DISPATCHED WITH THE DUAL SYS FULLY OPERATIVE. I ALSO FEEL THAT REDUCING CERTAIN AIR FIELDS TO ONLY AN EMER STATUS IS DEFINITELY REDUCING OUR CHOICES OF SUITABLE FIELDS.

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.