Narrative:

Cruise at FL370; center tank fuel reached 2000 pounds. I opened the crossfeed valve and no indication on the light. After replacing the bulbs; the light was still out. We checked circuit breaker panels and found the fuel crossfeed valve circuit breaker was open. We discussed and checked the fom. We reset the circuit breaker; tried the valve; and it showed closed; transient; then open. The circuit breaker popped; we discussed the situation and were unsure of the valve position. We ran the QRH for 'crossfeed valve inop' and discussed how to maintain fuel balance. We sent a message to dispatch concerning the crossfeed valve problem. We monitored the engines and all indications; fuel flow; and fuel quantity were normal. Once the center tank was depleted a rapid imbalance of 500 pounds in 5 minutes started with the #1 fuel tank quantity decreasing. We started the QRH checklist for 'fuel leak' and requested a descent from FL370 to FL290. We discussed turning off fuel boost pumps; but were unsure of the valve position; so we used differential thrust; to keep the imbalance below 1000 pounds. The note 2; in the fuel leak checklist states 'a fuel imbalance of 500 pounds or more within 30 minutes should be considered an engine fuel leak'. We asked the flight attendants to scan the #1 engine and look for fuel leaks. The flight attendants reported no visual indications. We contacted dispatch with a patch to maintenance control. We tried using all resources available but were unable to talk to maintenance control. We discussed the situation and concluded we had a fuel leak somewhere before the fuel control on the #1 engine. I told dispatch that we were declaring an emergency; shutting down #1 engine for a fuel leak and diverting. Dispatch approved the divert. We completed the fuel leak checklist and continued with the QRH engine failure/shutdown checklist and the one engine inoperative landing checklist. We told the flight attendants the situation and to secure the cabin for arrival. We made a brief PA to the passengers that we were diverting. We made an uneventful single engine heavy weight landing at 129;000 pounds. The touchdown was smooth and we released the emergency vehicles and taxied to the gate. On the ground; we made a PA to the passengers that we shut an engine down and we would coordinate with company to get them to their destination.I'm writing this safety report to highlight several discrepancies in the -700 QRH and -700 FM that needs to be addressed. QRH 'crossfeed valve inop'we were unsure of the valve position but assumed it failed in the open position.once the center tank was depleted; a rapid fuel lost/imbalance started in the #1 fuel tank. We discussed shutting off fuel pumps but were unsure if the valve was closed; partial closed/open would the engine flame out at FL370. We started a descent from FL370 to FL290 and used differential thrust; with #1 thrust lever near idle and #2 thrust lever midrange. We decided to keep the pumps on and use differential thrust to work the imbalance.QRH 'fuel leak'with the rapid fuel lost in #1 fuel tank; the indications showed a fuel leak; we complied with the procedures; reading all notes. Note 2 needs to be rewritten to bring in more information in determining a fuel leak. A note should be added concerning output pressure of main tank boost pumps can vary greatly and could lead you to believe that you had a fuel leak on the low tank. Fuel pumps- additional information should be provided to the flight crew that explains maintenance procedures do not check fuel boost pump output pressures and they can vary greatly per the manufacturer's specifications. Fuel crossfeed -- the sentence; 'continued crossfeed valve use will result in a progressive fuel imbalance.' this needs to be expanded to discuss fuel differential pressures could cause rapid fuel imbalance that could exceed the 1000 pound limit within a short period of time.

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Original NASA ASRS Text

Title: B737NG flight crew experienced fuel cross feed valve failed in the open position; which resulted in a rapid fuel imbalance once the center tank fuel was depleted. The crew assumed a fuel leak in the left engine and shuts it down in accordance with QRH procedures. Emergency was declared with a diversion to nearest suitable airport.

Narrative: Cruise at FL370; center tank fuel reached 2000 LBS. I opened the crossfeed valve and no indication on the light. After replacing the bulbs; the light was still out. We checked circuit breaker panels and found the fuel crossfeed valve circuit breaker was open. We discussed and checked the FOM. We reset the circuit breaker; tried the valve; and it showed closed; transient; then open. The circuit breaker popped; we discussed the situation and were unsure of the valve position. We ran the QRH for 'Crossfeed Valve Inop' and discussed how to maintain fuel balance. We sent a message to Dispatch concerning the crossfeed valve problem. We monitored the engines and all indications; fuel flow; and fuel quantity were normal. Once the center tank was depleted a rapid imbalance of 500 LBS in 5 minutes started with the #1 fuel tank quantity decreasing. We started the QRH checklist for 'Fuel Leak' and requested a descent from FL370 to FL290. We discussed turning off fuel boost pumps; but were unsure of the valve position; so we used differential thrust; to keep the imbalance below 1000 LBS. The note 2; in the Fuel Leak checklist states 'A fuel imbalance of 500 LBS or more within 30 minutes should be considered an engine fuel leak'. We asked the Flight Attendants to scan the #1 engine and look for fuel leaks. The Flight Attendants reported no visual indications. We contacted Dispatch with a patch to maintenance Control. We tried using all resources available but were unable to talk to maintenance Control. We discussed the situation and concluded we had a fuel leak somewhere before the fuel control on the #1 engine. I told dispatch that we were declaring an emergency; shutting down #1 engine for a fuel leak and diverting. Dispatch approved the divert. We completed the Fuel Leak checklist and continued with the QRH Engine Failure/Shutdown checklist and the One Engine Inoperative Landing checklist. We told the Flight Attendants the situation and to secure the cabin for arrival. We made a brief PA to the Passengers that we were diverting. We made an uneventful single engine heavy weight landing at 129;000 LBS. The touchdown was smooth and we released the emergency vehicles and taxied to the gate. On the ground; we made a PA to the passengers that we shut an engine down and we would coordinate with Company to get them to their destination.I'm writing this safety report to highlight several discrepancies in the -700 QRH and -700 FM that needs to be addressed. QRH 'Crossfeed Valve Inop'We were unsure of the valve position but assumed it failed in the open position.Once the center tank was depleted; a rapid fuel lost/imbalance started in the #1 fuel tank. We discussed shutting off fuel pumps but were unsure if the valve was closed; partial closed/open would the engine flame out at FL370. We started a descent from FL370 to FL290 and used differential thrust; with #1 thrust lever near idle and #2 thrust lever midrange. We decided to keep the pumps on and use differential thrust to work the imbalance.QRH 'Fuel Leak'With the rapid fuel lost in #1 fuel tank; the indications showed a fuel leak; we complied with the procedures; reading all notes. Note 2 needs to be rewritten to bring in more information in determining a fuel leak. A note should be added concerning output pressure of main tank boost pumps can vary greatly and could lead you to believe that you had a fuel leak on the low tank. Fuel pumps- Additional information should be provided to the Flight Crew that explains Maintenance procedures do not check fuel boost pump output pressures and they can vary greatly per the manufacturer's specifications. Fuel crossfeed -- The sentence; 'Continued crossfeed valve use will result in a progressive fuel imbalance.' This needs to be expanded to discuss fuel differential pressures could cause rapid fuel imbalance that could exceed the 1000 LB limit within a short period of time.

Data retrieved from NASA's ASRS site as of April 2012 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.