B737-500
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 151; Flight Crew Type 7700
Human-Machine Interface
Deviation - Altitude Undershoot; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Fuel Issue
Flight Crew Took Evasive Action; Flight Crew Became Reoriented
Aircraft; Human Factors
We were running about 20-30 minutes behind due to a late arriving aircraft into ZZZ with a Crew change.  As I did my preflight checks; I checked the crossfeed valve operation; and then must have been distracted by something else since I failed to close it after checking valve operation.  Following that; I did not recognize that it was left open until nearing our destination.  On my first fuel audit airborne; I saw that we were 300 pounds ahead of our burn plan; but I failed to check the balance once I noted that we were burning correctly.  Approaching our destination; however; I did another fuel check; and while we were still burning accurately; I recognized that we had a 4000 pound imbalance (1770 in left wing and 5750 in the right wing).  When I investigated; I realized that the crossfeed valve was open. I immediately started to try to balance the fuel; but knew that in the small amount of time we had left (and a lot of that would be in a descent) that we would need to do more than that to erase the imbalance.  We got into the QRH and the AOM to see if there were any information regarding our situation; but nothing was really applicable since it was a self-induced problem and not a fuel system malfunction.  Also at this time; we had been cleared to cross [a fix] at FL240; which we had programmed and had set.  This led to the first of a couple of workload errors.  While working on the problem; we got behind in our descent and crossed [the fix] about 600 feet to 700 feet high.  My initial thought was that I did not want to burn all the way down to just over 4000 pounds remaining; which is what it would take to balance the tanks.  Regardless; we put out the speedbrakes; started the APU; and eventually put out the gear and ten flaps (all well within altitude and speed parameters) in order to burn more gas.  I then started to coordinate with Maintenance and Dispatch to see if I could get relief from the 1000-pound imbalance limit or if I actually needed to burn all the gas.  During this coordination; we made our second Crew coordination error; we missed the Descent Checklist; which eventually led us to level off approximately 150 feet too high.  At that point; we ran the check and corrected our altitude.  Eventually we came to the conclusion that based on the VMC weather conditions we should continue to burn the fuel until we were within the 1000-pound limit.  We therefore coordinated for extended vectors and an extra 360-degree turn.  When we got down to an 800-pound imbalance on final; I closed the crossfeed valve.  We landed uneventfully with an 800-pound imbalance and approximately 4600 pounds total gas. First; extra diligence needs to be put into the flows we do especially when it comes to the major systems such as the fuel system.  Second; when issues come up; the Crew needs to really stay focused on flying first and foremost so we don't compound our problem with flying errors.  This division of workload would have prevented the missed crossing restriction and missed Descent Checklist.  Decision making between the Crew still needs to be a priority.  We reached our final course of action together; but it just can't interfere with the Pilot Flying and monitoring duties.
B737 Captain reports opening the fuel crossfeed valve during preflight and forgetting to close it. This results in a 4;000 pound fuel imbalance approaching destination. Gear and flaps are extended early and fuel consumed only from the heavy wing; to achieve an acceptable balance prior to landing.