B737-700
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted; Flight Crew Landed As Precaution; General Maintenance Action; General Declared Emergency
Aircraft
At approximately 10-15 minutes after level off at FL390 an IMBAL amber indication was noticed on the #2 main fuel tank. Fuel quantity indication for #1 gauge read 7.11 fuel indication on #2 gauge read 5.9. The #2 quantity was dropping rapidly and the #1 gauge was showing no fuel burn at all. The appropriate checklists were completed and determine that there was no fuel leak; however; when the imbalance was addressed it was found that the crossfeed valve was inoperative due to no blue light indications. It was subsequently determined that the crossfeed circuit breaker had popped. Since access to the fuel in #1 tank was in question; it was felt to be the safest course of action to divert the aircraft. An amended release was acquired from Dispatch; an emergency was declared and the aircraft was cleared and steered direct. An uneventful descent; approach; and landing was made with an imbalance in fuel tanks of approximately 1;600 LBS on touch down.
After a through preflight in which I checked all circuit breakers; we departed. About 10-15 after level off at FL390 I noticed the fuel imbalance annunciator. The left tank was 7.11 and the right was 6.89 and dropping rapidly. We accomplished three checklists. Starting with fuel imbalance QRH than proceeded to the fuel leak QRH. We determined we did not have a leak as the fuel on board was the same as what we computed should be remaining. We were burning fuel out of the right tank only. At that point we discovered that the crossfeed lights were what appeared to be burned out. We changed those and the light still did not test. It was at that point that we both saw that the crossfeed breaker had popped. We than did the crossfeed inoperative QRH; not knowing the fuel status of the left tank; this left us several options. At this point we could not determine what the position of the valve was and was probably open allowing the right boost pumps were most likely operating at a higher pressure to over power the left side. When we departed the switch was in the closed position. On descent and at a lower altitude with the engines at idle and fuel burning out of the right tank only; we 'opened' the crossfeed valve and began cross feeding normally. Approaching the final approach fix; the Captain repositioned the crossfeed and boost pumps to the normal positions and we made an uneventful landing.
B737 flight crew receives a fuel imbalance indication at FL390 and discovers that fuel is being used from the right tank only. The crossfeed valve is found to be inoperative with the circuit breaker tripped and the crew elects to divert to a suitable airport.