B737-800
Flight Crew Last 90 Days 75; Flight Crew Total 11500; Flight Crew Type 4300
Situational Awareness; Workload; Confusion; Troubleshooting
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action; General Declared Emergency
Aircraft
This flight is operated with a double crew of 2 captains and 2 first officers. On the return; 'A' crew is to operate the long leg. The 'B' crew operates the last legs and the 'A' crew rests. This report regards the final leg where I and my First Officer were the 'B' crew. We also carry a Maintenance Technician.Sometime after level off I noticed a rather large fuel imbalance; (tank #2 low). I turned the crossfeed valve knob to OPEN to balance the tanks. The cross feed 'OPEN' light did not illuminate. It was quickly determined that the cross feed valve circuit breaker was popped. I immediately summoned the onboard Maintenance Technician to determine if he could suggest any alternate procedure or if Maintenance Control could suggest anything. The Technician suggested that we try to reset the crossfeed valve circuit breaker. I directed the Technician to reset the circuit breaker which was ineffective; the breaker would not hold; even momentarily. Now the IMBAL amber caution is illuminated; on the Number 2 fuel tank quantity display. We ran the Crossfeed Valve Selector Inoperative Checklist and Engine Fuel Leak Checklist. Considering our fuel status we did not suspect a fuel leak. It just appeared that most of the fuel was being used from the Number 2 tank and the Number 1 tank was feeding very slowly. I verified 'sufficient fuel is available for both engines to complete the flight' as noted in the Crossfeed Valve Selector Inoperative Checklist. At that time I determined; considering our fuel status and weather conditions; distance to Top of Descent (TOD); etc. that the safest course of action was to continue to our filed destination. Also; in an abundance of caution; I decided to declare an emergency; to ensure ATC priority handling; and make all available resources aware of our situation. The 'A' crew Captain was summoned to the cockpit jumpseat to act as a third set of eyes and to assist with communications. I spoke to the Purser and briefly explained the nature of the emergency and told him to expect normal approach and landing and not to expect an EVAC.Maintenance Control was notified by SATCOM. A normal visual approach was made. Although we had an IMBAL of about 3;000 LBS aircraft handling was normal. I stopped between the runways for visual inspection by Airport Fire Department vehicles. At first they said we looked normal; then sometime shortly later a responder; on the Tower frequency; said fuel was leaking from Number 2 Engine; I shutdown and had us towed to parking. Apparently this was inaccurate as there was no leak.In the aircraft log I wrote up cross feed circuit breaker popped in flight; unable to cross feed; and Number 2 Engine fuel leak reported by Fire Department. Local Maintenance technicians told me at the gate that they verified the Crossfeed Valve stuck in a partially open position causing the IMBAL. Maintenance said there was no fuel leak and surmised the Fire Department mistook puddles on taxiway from recent rain for fuel.
[Report narrative contained no additional information].
A B737-800 Fuel Crossfeed Valve failed partially open with a tripped circuit breaker which caused a FUEL IMBAL alert as tank two fed both engines. An emergency was declared as the flight proceeded directly to its destination where it landed with a 3;000 LBS imbalance.