Date: 201402
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Fuel Crossfeed
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Human factors: Situational Awareness; Training / Qualification; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; General Maintenance Action
Contributing factors: Procedure; Aircraft; Manuals
Primary problem: Aircraft

Narrative: At cruise I discovered a fuel imbalance occurring; so I attempted to crossfeed. The crossfeed light did not come on when I turned the knob. After changing the bulbs; the light did not come on so I checked circuit breakers. The crossfeed circuit breaker was open. The First Officer and I confirmed that the crossfeed circuit breaker is not one of the fuel circuit breakers in the Limitations section that should never be reset. We reviewed the limitation concerning an in-flight reset of an open circuit breaker. The fuel imbalance was continuing to increase so we decided that fuel management was critical to the safe completion of the flight. I directed the First Officer to close the circuit breaker. The crossfeed operated normally. We were able to fix the imbalance and the flight continued uneventfully. Later; reviewing the QRH Fuel section; I noticed a checklist for Crossfeed Selector Inoperative; which addresses an open crossfeed circuit breaker. The QRH says 'to verify sufficient fuel is available to both engines to complete the flight. STOP.' It does not direct closing the circuit breaker. We did have enough fuel for both engines to complete the flight even if most of the fuel came from one tank. However; by the time we closed the circuit breaker; the imbalance had increased to 900 LBS. We burned another 2;000 LBS to the destination. So we could have developed a significant fuel imbalance unless we diverted. I should have looked in the QRH for an applicable checklist before resetting the circuit breaker. Also; although I knew the limitations concerning circuit breakers and the First Officer and I actually got them out and reviewed them before resetting the circuit breaker. I didn't understand how to apply it. I thought fuel management was critical to the safe completion of the flight but It seems that 'critical to the safe completion of the flight' means you can't even make it to a divert field unless you reset this circuit breaker. Furthermore; the fuel imbalance is not addressed with the crossfeed valve circuit breaker tripped. In our case; this would have definitely exceeded the 1;000 LBS limit even if we diverted. I'm still investigating but I'm still not clear on how big the imbalance can safely be? I'm not sure how to prevent this situation again. Perhaps training could emphasize the 'critical to the safe completion of the flight' limitation with a few examples of acceptable critical items.




Synopsis: A B737-700 crew discovered the fuel crossfeed circuit breaker was open causing a fuel imbalance so after reviewing the QRH; which was inconclusive; the circuit breaker was reset permitting normal crossfeed operations and preventing a diversion for fuel imbalance.