Narrative:

At XA25Z; cruising at FL360 in VMC flight conditions; and while performing a cruise so panel check; I observed the #4 engine nacelle temperature indicator fluctuating rapidly initially between 4 and 8 causing an intermittent illumination of the amber fault light. I notified the captain of the condition; got out the communication (crew operating manual) to preview the procedures. Within a few mins the nacelle temperature indicator went above 8 and stayed in the 8-10 range with the fault light on steady. Performed the communication (crew operating manual) procedure and determined that a fault condition existed on the a loop. Switch was placed to the B position. Within a very short time; the captain detected the odor of electrical fumes; and then a short time later the first officer and I concurred with the smell of electrical fumes. I looked to the location of the engine fire detect circuit breakers and observed all circuit breakers normal; however; I did notice an orange glow through small openings in the P6 circuit breaker panel. I walked around to the side and rear of the P6 panel looking through the observation ports. On the upper rear portion of the P6 panel; I observed smoke and flames visible through the upper observation port. I informed the captain and began the red bordered electrical fire or smoke checklist. Oxygen masks donned; but did not put on smoke goggles; as the smoke was minimal at this point. Time elapsed now is maybe 5 mins; and an emergency descent and diversion initiated. I continued the electrical fire or smoke checklist. I continued to check the rear of the P6 panel; though it was difficult to do so with the oxygen mask on due to length of hose and unable to communicate with the mask on due to no hot microphone capability. The fire/flames had now increased in intensity and clearly visible through observation ports. The captain directed me to dump fuel and I dumped 10000 pounds of fuel to an aircraft weight of about 628000 pounds. Dump terminated above 10000 ft AGL. All so electrical panel indications observed to be normal. I continued to check the status of the fire and the flames continued to increase in strength and seemed to be spreading wider. I now noticed that the engine fire detect 3A-4A circuit breaker was tripped. At this time; I noticed the fire/flames beginning to diminish in intensity. I attempted a brief radio call to dispatch; but got no response. I performed descent and approach checklists; provided the landing data to the pilots; sent an ACARS divert message to dispatch; and contacted ZZZZ operations via VHF radio. Since only faint smell of fumes existed; I removed my oxygen mask to make it easier to communicate with the pilots. Quickly checked the P6 panel one more time; and observed the fire out. On downwind leg abeam the airfield; I observed the APU fire detection a fault light on. However; APU was MEL'ed inoperative and deactivated. A normal landing was made on runway 36. After exiting the runway; we were instructed to hold position on the parallel taxiway while fire and rescue checked the exterior of the aircraft. With fire captain's approval and the fire apparently out in the cockpit; we taxied to parking. After aircraft parked and airstairs pulled up to the door L1; several fire and rescue personnel entered the cockpit; accompanied by customs officials. Fire and rescue personnel wanted to see the inside of the engine fire control panel on the rear of the P6 panel. Since electrical power was applied to the aircraft via external power cart; I elected to pull the remaining 3 engine fire detect circuit breakers; as well as the APU fire detect circuit breaker before allowing the panel on the rear of the P6 panel to be opened. However; these circuit breakers were extremely difficult to pull; requiring abnormal force to pull them out. Access required the removal of 4 phillips head screws. Fire and rescue observed obvious evidence of fire on one or more of the circuit boards. Fire and rescue personnel determined the fire to be out and no further action by fire and rescue personnel required. Supplemental information from acn 743419: the time elapsed from the first indication of any problem until we were on the ground was approximately 25 mins.

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Original NASA ASRS Text

Title: A B747-200 CREW REPORTS SEVERAL FIRE DETECTION CIRCUIT BREAKER CIRCUIT BOARDS CAUGHT FIRE IN FLT RESULTING IN AN EMERGENCY DIVERSION.

Narrative: AT XA25Z; CRUISING AT FL360 IN VMC FLT CONDITIONS; AND WHILE PERFORMING A CRUISE SO PANEL CHK; I OBSERVED THE #4 ENG NACELLE TEMP INDICATOR FLUCTUATING RAPIDLY INITIALLY BTWN 4 AND 8 CAUSING AN INTERMITTENT ILLUMINATION OF THE AMBER FAULT LIGHT. I NOTIFIED THE CAPT OF THE CONDITION; GOT OUT THE COM (CREW OPERATING MANUAL) TO PREVIEW THE PROCS. WITHIN A FEW MINS THE NACELLE TEMP INDICATOR WENT ABOVE 8 AND STAYED IN THE 8-10 RANGE WITH THE FAULT LIGHT ON STEADY. PERFORMED THE COM (CREW OPERATING MANUAL) PROC AND DETERMINED THAT A FAULT CONDITION EXISTED ON THE A LOOP. SWITCH WAS PLACED TO THE B POS. WITHIN A VERY SHORT TIME; THE CAPT DETECTED THE ODOR OF ELECTRICAL FUMES; AND THEN A SHORT TIME LATER THE FO AND I CONCURRED WITH THE SMELL OF ELECTRICAL FUMES. I LOOKED TO THE LOCATION OF THE ENG FIRE DETECT CIRCUIT BREAKERS AND OBSERVED ALL CIRCUIT BREAKERS NORMAL; HOWEVER; I DID NOTICE AN ORANGE GLOW THROUGH SMALL OPENINGS IN THE P6 CIRCUIT BREAKER PANEL. I WALKED AROUND TO THE SIDE AND REAR OF THE P6 PANEL LOOKING THROUGH THE OBSERVATION PORTS. ON THE UPPER REAR PORTION OF THE P6 PANEL; I OBSERVED SMOKE AND FLAMES VISIBLE THROUGH THE UPPER OBSERVATION PORT. I INFORMED THE CAPT AND BEGAN THE RED BORDERED ELECTRICAL FIRE OR SMOKE CHKLIST. OXYGEN MASKS DONNED; BUT DID NOT PUT ON SMOKE GOGGLES; AS THE SMOKE WAS MINIMAL AT THIS POINT. TIME ELAPSED NOW IS MAYBE 5 MINS; AND AN EMER DSCNT AND DIVERSION INITIATED. I CONTINUED THE ELECTRICAL FIRE OR SMOKE CHKLIST. I CONTINUED TO CHK THE REAR OF THE P6 PANEL; THOUGH IT WAS DIFFICULT TO DO SO WITH THE OXYGEN MASK ON DUE TO LENGTH OF HOSE AND UNABLE TO COMMUNICATE WITH THE MASK ON DUE TO NO HOT MIKE CAPABILITY. THE FIRE/FLAMES HAD NOW INCREASED IN INTENSITY AND CLRLY VISIBLE THROUGH OBSERVATION PORTS. THE CAPT DIRECTED ME TO DUMP FUEL AND I DUMPED 10000 LBS OF FUEL TO AN ACFT WT OF ABOUT 628000 LBS. DUMP TERMINATED ABOVE 10000 FT AGL. ALL SO ELECTRICAL PANEL INDICATIONS OBSERVED TO BE NORMAL. I CONTINUED TO CHK THE STATUS OF THE FIRE AND THE FLAMES CONTINUED TO INCREASE IN STRENGTH AND SEEMED TO BE SPREADING WIDER. I NOW NOTICED THAT THE ENG FIRE DETECT 3A-4A CIRCUIT BREAKER WAS TRIPPED. AT THIS TIME; I NOTICED THE FIRE/FLAMES BEGINNING TO DIMINISH IN INTENSITY. I ATTEMPTED A BRIEF RADIO CALL TO DISPATCH; BUT GOT NO RESPONSE. I PERFORMED DSCNT AND APCH CHKLISTS; PROVIDED THE LNDG DATA TO THE PLTS; SENT AN ACARS DIVERT MESSAGE TO DISPATCH; AND CONTACTED ZZZZ OPS VIA VHF RADIO. SINCE ONLY FAINT SMELL OF FUMES EXISTED; I REMOVED MY OXYGEN MASK TO MAKE IT EASIER TO COMMUNICATE WITH THE PLTS. QUICKLY CHKED THE P6 PANEL ONE MORE TIME; AND OBSERVED THE FIRE OUT. ON DOWNWIND LEG ABEAM THE AIRFIELD; I OBSERVED THE APU FIRE DETECTION A FAULT LIGHT ON. HOWEVER; APU WAS MEL'ED INOP AND DEACTIVATED. A NORMAL LNDG WAS MADE ON RWY 36. AFTER EXITING THE RWY; WE WERE INSTRUCTED TO HOLD POS ON THE PARALLEL TXWY WHILE FIRE AND RESCUE CHKED THE EXTERIOR OF THE ACFT. WITH FIRE CAPT'S APPROVAL AND THE FIRE APPARENTLY OUT IN THE COCKPIT; WE TAXIED TO PARKING. AFTER ACFT PARKED AND AIRSTAIRS PULLED UP TO THE DOOR L1; SEVERAL FIRE AND RESCUE PERSONNEL ENTERED THE COCKPIT; ACCOMPANIED BY CUSTOMS OFFICIALS. FIRE AND RESCUE PERSONNEL WANTED TO SEE THE INSIDE OF THE ENG FIRE CTL PANEL ON THE REAR OF THE P6 PANEL. SINCE ELECTRICAL PWR WAS APPLIED TO THE ACFT VIA EXTERNAL PWR CART; I ELECTED TO PULL THE REMAINING 3 ENG FIRE DETECT CIRCUIT BREAKERS; AS WELL AS THE APU FIRE DETECT CIRCUIT BREAKER BEFORE ALLOWING THE PANEL ON THE REAR OF THE P6 PANEL TO BE OPENED. HOWEVER; THESE CIRCUIT BREAKERS WERE EXTREMELY DIFFICULT TO PULL; REQUIRING ABNORMAL FORCE TO PULL THEM OUT. ACCESS REQUIRED THE REMOVAL OF 4 PHILLIPS HEAD SCREWS. FIRE AND RESCUE OBSERVED OBVIOUS EVIDENCE OF FIRE ON ONE OR MORE OF THE CIRCUIT BOARDS. FIRE AND RESCUE PERSONNEL DETERMINED THE FIRE TO BE OUT AND NO FURTHER ACTION BY FIRE AND RESCUE PERSONNEL REQUIRED. SUPPLEMENTAL INFO FROM ACN 743419: THE TIME ELAPSED FROM THE FIRST INDICATION OF ANY PROB UNTIL WE WERE ON THE GND WAS APPROX 25 MINS.

Data retrieved from NASA's ASRS site as of January 2009 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.