SF 340B
Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
General Maintenance Action
Aircraft; Human Factors
Our planned fuel on board was 2;800 LBS. When I was filling out the weight and balance form; I looked at the fuel gauges and saw 2;800 LBS. When the Captain and I ran the Before Start Checklist we stated '2;800 LBS on board;' because that is what we saw. We safely completed the flight. During my preflight for the return flight; I noted the fuel on board to be 3;400 LBS. I looked at the release and saw our planned fuel on board to be 2;200 LBS. I informed the Captain that we had been over fueled. We called the fueler and they informed us they had not fueled us. At this point; we began to question the integrity of the fuel quantity gauges. The questioning arose because aircraft had MEL's for the fuel flow gauges and the fuel used indicator (fuel totalizer). The MEL numbers are 73-32-1 and 73-32-2. The Captain called Dispatch to make them aware of what was going on and was then transferred to Maintenance Control. The Captain explained the situation to Maintenance Control and expressed that he and I felt the fuel quantity gauges were malfunctioning. Maintenance Control had Contract Maintenance come out to test the fuel quantity gauges. Contract Maintenance preformed the tests and left. At this point; Maintenance Control became concerned we landed overweight or exceeded structural limitations and that an overweight inspection would need to be completed. We assured them we had not landed overweight or exceeded any structural limitations. We know we didn't land overweight or exceed any structural limitations; because Maintenance had us complete a new weight and balance form using the fuel quantity the gauges currently read plus our fuel burn from the release and the original load manifest. The fuel quantity the gauges currently read was 3;400 LBS; and our burn from the release was 502 LBS plus 100 LBS for taxi for a total of 4;002 LBS. This weight and balance calculation satisfied Maintenance Control; and they agreed they did not need to send a 'road crew' to perform an overweight landing inspection. Maintenance Control then felt Contract Maintenance needed to come back over to sign off the aircraft logbook with the appropriate corrective action.
Aircraft shut down at gate with fuel totalizer showing a 500 LBS burn. Aircraft re-powered during boarding. First Officer noticed during filling out of the weight and balance form that the Fuel on Board (FOB) was indicating 3;400 LBS. This was brought to my attention immediately. We both were under this assumption that we must have been fueled at the gate by the fuel truck after arrival. Contacted Dispatch; finding out that no fuel operations happened; we did not know where the fuel indications came from. 2;800 LBS minus 502 burn and 100 taxi should have left aircraft with 2;198 LBS on board. Aircraft was deplaned and the aircraft was written up for inaccurate fuel quantity gauges. Contract Maintenance inspected this aircraft; to see if the gauges were faulty. After the aircraft was signed off we did a new Weight and Balance using the current FOB and continued with a normal flight.
SF340 flight crew reports departing with 2;800 LBS of fuel on board then discovering during preflight for the next leg that is the gauges indicated 3;400 LBS of fuel on board; although none was added.