Narrative:

We landed at the airport and were taxiing to the gate. Our gate was unavailable due to a ground stop being in effect for another major airport. We were forced to hold on the taxiway while we waited for our gate. During the wait the APU was running and the #2 engine was shut down. The delay was extensive enough that a fuel imbal occurred between the #1 and #2 fuel tanks. The xfeed valve selector was positioned to xfeed but no in transit light or valve open light illuminated. The selector was placed back to closed and then placed back to open. The valve cycled open on the second attempt and the indicators functioned normally. The valve was cycled closed and back to open to see if the problem would duplicate itself and to gather more information to pass on to our company maintenance department. This time when the selector was placed to the open position the indicator light showed the valve in transit and then open. After a very short time the indicator light flickered between open and in transit several times and then went blank. The valve selector was not moved during this time. The selector was cycled again and the valve and indicators functioned normally. Normal fuel xfeeding was accomplished. A gate opened up and we proceeded to the blocks. Maintenance was advised and they decided to change the xfeed valve actuator. The actuator was changed and the ground test showed normal operation of the valve and indicators. The aircraft was released and we set off in the same aircraft to fly the remaining 5 legs that we were scheduled for that day. On the next 3 legs the valve was used and all indications for the valve as well as normal fuel xfeed capability were observed. Problem solved, or so we thought. On leg #5 we leveled in cruise at FL370. A slight imbal was again present between the #1 and #2 main fuel tanks. The xfeed selector was positioned to open and once again there was no corresponding change to the position indicators. The light remained blank. The selector was cycled and the proper indications were observed. Each wing tank was about one halffull at approximately 5500 pounds each. Both boost pumps in the #2 tank were positioned to off in order to xfeed from #1 tank to the #2 engine. I looked down at the fuel gauges to insure that xfeeding was actually occurring. Something didn't look quite right. The fuel quantity in the #1 tank was not decreasing as fast as it should. We encountered some very light turbulence, 1 or 2 bumps, and this caused the readings on both indicators to fluctuate. As I waited for the gauges to settle down, ATC called and issued us a clearance to turn right for delaying vectors to the arrival airport. The a autoplt was flying the airplane in LNAV and VNAV. Heading select was selected and the heading bug was rotated to the desired heading. The bank selector was still set for 25 degrees from the departure. I was looking at the fuel gauges again to determine if fuel xfeeding was in fact occurring. At this point the copilot noticed the autoplt overshot the desired heading. I looked up to see if the autoplt was still in the heading mode. It was. As I worked to return the autoplt to the desired heading I said, 'now why did it do that?' at this moment, the #2 generator off bus and bus off lights illuminated. I reached up and attempted to put the generator back on the bus. It immediately tripped back off. I quickly scanned the engine instruments and discovered that the #2 engine had flamed out. I disconnected the autoplt and rolled the wings level. I immediately placed both #2 fuel boost pumps to on and observed the low pressure lights extinguish. I reached over to close the xfeed selector. I observed that the xfeed valve indicator was blank. I positioned the xfeed selector to close and turned the ignitors to flight start. Engine parameters were checked and found to be normal. The engine did not relight. We placed the #2 start lever to off and retarded the #2 throttle to idle. We waited, and then returned the start lever to idle. The engine did not restart. At this point we requested a lower altitude from ATC. ATC advised us that they were unable a lower altitude. An emergency was declared and dscntwas initiated. The airspeed at this point had decayed to approximately 180 KIAS. A buffet alert message was displayed on the FMC and the start of pre- stall buffet was felt as the nose was pushed over for the descent. We believed that the flameout was related to the malfunctioning xfeed valve and with all other engine indications normal, the engine in-flight start checklist was run and a windmilling start was attempted. The engine lit-off, but hung and egt was observed increasing. The start lever was placed to off. The airplane had descended to the high 20's and the APU was successfully started and used to power the #2 generator bus. At this time we attempted a starter assisted start. The engine started normally and stabilized. The throttle was advanced and the engine spooled up to normal cruise power and stabilized. The drift down descent was stopped at FL250. The engine generator was used to power its own bus. The APU was left running, just in case. ATC and dispatch were advised that the engine had restarted and that we were proceeding to our planned destination. Maintenance was advised to meet the flight. The remainder of the flight was uneventful. Maintenance was briefed in the cockpit and all of the problem indications were duplicated in the cockpit. The aircraft was withdrawn from service. We picked up another airplane and completed our sixth and final leg of the day normally.

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Original NASA ASRS Text

Title: B737-500 FL370 ON SADDE STAR, DERBB TRANSITION, BALANCING FUEL, HAS FLAMEOUT #2 ENG. MAINT HAD REPLACED XFEED VALVE EARLIER IN THE DAY. CREW DECLARED EMER AND BEGAN A DSCNT AND WAS ABLE TO RESTART ENG AT LOWER LEVEL. CONTINUED TO LAX AND LANDED NORMALLY.

Narrative: WE LANDED AT THE ARPT AND WERE TAXIING TO THE GATE. OUR GATE WAS UNAVAILABLE DUE TO A GND STOP BEING IN EFFECT FOR ANOTHER MAJOR ARPT. WE WERE FORCED TO HOLD ON THE TXWY WHILE WE WAITED FOR OUR GATE. DURING THE WAIT THE APU WAS RUNNING AND THE #2 ENG WAS SHUT DOWN. THE DELAY WAS EXTENSIVE ENOUGH THAT A FUEL IMBAL OCCURRED BTWN THE #1 AND #2 FUEL TANKS. THE XFEED VALVE SELECTOR WAS POSITIONED TO XFEED BUT NO IN TRANSIT LIGHT OR VALVE OPEN LIGHT ILLUMINATED. THE SELECTOR WAS PLACED BACK TO CLOSED AND THEN PLACED BACK TO OPEN. THE VALVE CYCLED OPEN ON THE SECOND ATTEMPT AND THE INDICATORS FUNCTIONED NORMALLY. THE VALVE WAS CYCLED CLOSED AND BACK TO OPEN TO SEE IF THE PROB WOULD DUPLICATE ITSELF AND TO GATHER MORE INFO TO PASS ON TO OUR COMPANY MAINT DEPT. THIS TIME WHEN THE SELECTOR WAS PLACED TO THE OPEN POS THE INDICATOR LIGHT SHOWED THE VALVE IN TRANSIT AND THEN OPEN. AFTER A VERY SHORT TIME THE INDICATOR LIGHT FLICKERED BTWN OPEN AND IN TRANSIT SEVERAL TIMES AND THEN WENT BLANK. THE VALVE SELECTOR WAS NOT MOVED DURING THIS TIME. THE SELECTOR WAS CYCLED AGAIN AND THE VALVE AND INDICATORS FUNCTIONED NORMALLY. NORMAL FUEL XFEEDING WAS ACCOMPLISHED. A GATE OPENED UP AND WE PROCEEDED TO THE BLOCKS. MAINT WAS ADVISED AND THEY DECIDED TO CHANGE THE XFEED VALVE ACTUATOR. THE ACTUATOR WAS CHANGED AND THE GND TEST SHOWED NORMAL OP OF THE VALVE AND INDICATORS. THE ACFT WAS RELEASED AND WE SET OFF IN THE SAME ACFT TO FLY THE REMAINING 5 LEGS THAT WE WERE SCHEDULED FOR THAT DAY. ON THE NEXT 3 LEGS THE VALVE WAS USED AND ALL INDICATIONS FOR THE VALVE AS WELL AS NORMAL FUEL XFEED CAPABILITY WERE OBSERVED. PROB SOLVED, OR SO WE THOUGHT. ON LEG #5 WE LEVELED IN CRUISE AT FL370. A SLIGHT IMBAL WAS AGAIN PRESENT BTWN THE #1 AND #2 MAIN FUEL TANKS. THE XFEED SELECTOR WAS POSITIONED TO OPEN AND ONCE AGAIN THERE WAS NO CORRESPONDING CHANGE TO THE POS INDICATORS. THE LIGHT REMAINED BLANK. THE SELECTOR WAS CYCLED AND THE PROPER INDICATIONS WERE OBSERVED. EACH WING TANK WAS ABOUT ONE HALFFULL AT APPROX 5500 LBS EACH. BOTH BOOST PUMPS IN THE #2 TANK WERE POSITIONED TO OFF IN ORDER TO XFEED FROM #1 TANK TO THE #2 ENG. I LOOKED DOWN AT THE FUEL GAUGES TO INSURE THAT XFEEDING WAS ACTUALLY OCCURRING. SOMETHING DIDN'T LOOK QUITE RIGHT. THE FUEL QUANTITY IN THE #1 TANK WAS NOT DECREASING AS FAST AS IT SHOULD. WE ENCOUNTERED SOME VERY LIGHT TURB, 1 OR 2 BUMPS, AND THIS CAUSED THE READINGS ON BOTH INDICATORS TO FLUCTUATE. AS I WAITED FOR THE GAUGES TO SETTLE DOWN, ATC CALLED AND ISSUED US A CLRNC TO TURN R FOR DELAYING VECTORS TO THE ARR ARPT. THE A AUTOPLT WAS FLYING THE AIRPLANE IN LNAV AND VNAV. HDG SELECT WAS SELECTED AND THE HDG BUG WAS ROTATED TO THE DESIRED HDG. THE BANK SELECTOR WAS STILL SET FOR 25 DEGS FROM THE DEP. I WAS LOOKING AT THE FUEL GAUGES AGAIN TO DETERMINE IF FUEL XFEEDING WAS IN FACT OCCURRING. AT THIS POINT THE COPLT NOTICED THE AUTOPLT OVERSHOT THE DESIRED HDG. I LOOKED UP TO SEE IF THE AUTOPLT WAS STILL IN THE HDG MODE. IT WAS. AS I WORKED TO RETURN THE AUTOPLT TO THE DESIRED HDG I SAID, 'NOW WHY DID IT DO THAT?' AT THIS MOMENT, THE #2 GENERATOR OFF BUS AND BUS OFF LIGHTS ILLUMINATED. I REACHED UP AND ATTEMPTED TO PUT THE GENERATOR BACK ON THE BUS. IT IMMEDIATELY TRIPPED BACK OFF. I QUICKLY SCANNED THE ENG INSTS AND DISCOVERED THAT THE #2 ENG HAD FLAMED OUT. I DISCONNECTED THE AUTOPLT AND ROLLED THE WINGS LEVEL. I IMMEDIATELY PLACED BOTH #2 FUEL BOOST PUMPS TO ON AND OBSERVED THE LOW PRESSURE LIGHTS EXTINGUISH. I REACHED OVER TO CLOSE THE XFEED SELECTOR. I OBSERVED THAT THE XFEED VALVE INDICATOR WAS BLANK. I POSITIONED THE XFEED SELECTOR TO CLOSE AND TURNED THE IGNITORS TO FLT START. ENG PARAMETERS WERE CHKED AND FOUND TO BE NORMAL. THE ENG DID NOT RELIGHT. WE PLACED THE #2 START LEVER TO OFF AND RETARDED THE #2 THROTTLE TO IDLE. WE WAITED, AND THEN RETURNED THE START LEVER TO IDLE. THE ENG DID NOT RESTART. AT THIS POINT WE REQUESTED A LOWER ALT FROM ATC. ATC ADVISED US THAT THEY WERE UNABLE A LOWER ALT. AN EMER WAS DECLARED AND DSCNTWAS INITIATED. THE AIRSPD AT THIS POINT HAD DECAYED TO APPROX 180 KIAS. A BUFFET ALERT MESSAGE WAS DISPLAYED ON THE FMC AND THE START OF PRE- STALL BUFFET WAS FELT AS THE NOSE WAS PUSHED OVER FOR THE DSCNT. WE BELIEVED THAT THE FLAMEOUT WAS RELATED TO THE MALFUNCTIONING XFEED VALVE AND WITH ALL OTHER ENG INDICATIONS NORMAL, THE ENG INFLT START CHKLIST WAS RUN AND A WINDMILLING START WAS ATTEMPTED. THE ENG LIT-OFF, BUT HUNG AND EGT WAS OBSERVED INCREASING. THE START LEVER WAS PLACED TO OFF. THE AIRPLANE HAD DSNDED TO THE HIGH 20'S AND THE APU WAS SUCCESSFULLY STARTED AND USED TO PWR THE #2 GENERATOR BUS. AT THIS TIME WE ATTEMPTED A STARTER ASSISTED START. THE ENG STARTED NORMALLY AND STABILIZED. THE THROTTLE WAS ADVANCED AND THE ENG SPOOLED UP TO NORMAL CRUISE PWR AND STABILIZED. THE DRIFT DOWN DSCNT WAS STOPPED AT FL250. THE ENG GENERATOR WAS USED TO PWR ITS OWN BUS. THE APU WAS LEFT RUNNING, JUST IN CASE. ATC AND DISPATCH WERE ADVISED THAT THE ENG HAD RESTARTED AND THAT WE WERE PROCEEDING TO OUR PLANNED DEST. MAINT WAS ADVISED TO MEET THE FLT. THE REMAINDER OF THE FLT WAS UNEVENTFUL. MAINT WAS BRIEFED IN THE COCKPIT AND ALL OF THE PROB INDICATIONS WERE DUPLICATED IN THE COCKPIT. THE ACFT WAS WITHDRAWN FROM SVC. WE PICKED UP ANOTHER AIRPLANE AND COMPLETED OUR SIXTH AND FINAL LEG OF THE DAY NORMALLY.

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.