Narrative:

We arrived at the aircraft with time to spare and began our preflight duties. The first officer discovered a discrepancy with the APU fire detection system and maintenance was called to defer the system. We then performed the before start originating checklist and noted a fuel load of 20.7 which is what was required by the release. The first officer and I noted that both main tank fuel gauges read 10;000 lbs with another 700 lbs in the center tank. We received the loadsheet and performed the before push check. We started the engines at the gate due to our APU being deferred and pushed from the gate. Taxi out was normal and we were cleared to takeoff runway xxl with a 350 heading after departure. On departure; I noticed that I needed a considerable amount of aileron to keep the wings level. I started to trouble shoot the problem when we were cleared direct. We then received a CDU message that we would be using reserve fuel upon arrival with an arrival fuel of 5.1. The CDU then updated twice more settling on an arrival fuel of 3.7. The first officer and I then noticed that the #1 main fuel gauge was now 4000 lbs less than the #2 fuel gauge. I transferred control to the first officer and contacted dispatch. The decision to return to our departure city was made. The approach and landing was uneventful. After arrival at the gate; I evaluated our performance and found that I had not checked the fuel upload with my calculations. When I checked the loadsheet there was a 4000 lb difference. Maintenance deferred the gauge; the aircraft was fueled and dripsticked; and the flight continued uneventfully. I take full responsibility for the error. I saw what I wanted to see on the fuel gauges and did not cross check the upload as is required per the fom. I believe that the issues with the APU and the fact that we were not sure if deicing would be needed distracted me. I glossed over a very important task. I need to make sure that I slow down and check everything I need to on the loadsheet so as not to allow this to happen again.

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Original NASA ASRS Text

Title: A B737-300 crew departed after ensuring the fuel load displayed on the fuel tank gauges was the required fuel. After takeoff; an aileron trim requirement lead to discovering a number one fuel tank gauge error. The fuel uploaded was too little because the gauge incorrectly indicated the proper fuel.

Narrative: We arrived at the aircraft with time to spare and began our preflight duties. The First Officer discovered a discrepancy with the APU fire detection system and Maintenance was called to defer the system. We then performed the Before Start Originating checklist and noted a fuel load of 20.7 which is what was required by the Release. The First Officer and I noted that both main tank fuel gauges read 10;000 lbs with another 700 lbs in the center tank. We received the loadsheet and performed the Before Push check. We started the engines at the gate due to our APU being deferred and pushed from the gate. Taxi out was normal and we were cleared to takeoff Runway XXL with a 350 heading after departure. On departure; I noticed that I needed a considerable amount of aileron to keep the wings level. I started to trouble shoot the problem when we were cleared direct. We then received a CDU message that we would be using reserve fuel upon arrival with an arrival fuel of 5.1. The CDU then updated twice more settling on an arrival fuel of 3.7. The First Officer and I then noticed that the #1 main fuel gauge was now 4000 lbs less than the #2 fuel gauge. I transferred control to the First Officer and contacted Dispatch. The decision to return to our departure city was made. The approach and landing was uneventful. After arrival at the gate; I evaluated our performance and found that I had not checked the fuel upload with my calculations. When I checked the loadsheet there was a 4000 lb difference. Maintenance deferred the gauge; the aircraft was fueled and dripsticked; and the flight continued uneventfully. I take full responsibility for the error. I saw what I wanted to see on the fuel gauges and did not cross check the upload as is required per the FOM. I believe that the issues with the APU and the fact that we were not sure if deicing would be needed distracted me. I glossed over a very important task. I need to make sure that I slow down and check everything I need to on the loadsheet so as not to allow this to happen again.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.