B737 Undifferentiated or Other Model
Flight Crew Last 90 Days 150; Flight Crew Total 5000; Flight Crew Type 697
Distraction
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
General None Reported / Taken
Human Factors
Numerous little distractions kept us from noticing that the fuel was out of balance until after takeoff.  Distractions included being a day late due to a mechanical; 35-minute late van; aircraft not being at the gate when we arrived; aircraft not cleaned or catered; aircraft repair not complete due to contract-maintenance error; late fuel slip; late final weights; communication with load planning about need to move passengers for balance; inop VNAV; NADP1 departure; ACARS2 and Sabre learning curve.  Additional factors include the fact that because we dispatched with fuel on board (from our cancelled flight the night before) a fueler never had the chance to fix the imbalance.  Finally; we suspect the yellow IMBAL annunciation did not catch our attention because we are so used to seeing the yellow CONFIG annunciation on takeoff.  Also; we have gotten used to just looking at the total fuel indication; and we forget to check the individual tanks for balance.  We assume the imbalance was created by extensive APU use by the tow crew the day prior.  Enough fuel was burned to indicate that the APU was running for many hours.  We should have caught this imbalance on the preflight but missed it.  It's noteworthy that before push we discussed feeling like we had lots of little alligators at our heels; one got us.
B737 First Officer reported departing with fuel out of balance; citing a number of distractions as contributory.