Date: 201508
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Fuel Quantity-Pressure Indication
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; General Maintenance Action
Contributing factors: Aircraft; Procedure
Primary problem: Aircraft

Narrative: Aircraft arrived late. Did not see this crew. MX write up APU overspeed on start. APU MEL'd. During preflight noticed a lot of left rudder trim; approximately 3 units. Centered it. Departed; FO flying; and I noticed he was having to apply a lot of left aileron so suggested he trim it up with some rudder trim. TOC did my fuel calculations on the flight plan and saw we should arrive with about 6.9 on the gas. 400 lb imbalance at TOC left tank low; so balanced fuel. Abeam ZZZ again saw a 400 lb imbalance; again left tank low. Balanced for the last time. Abeam ZZZ1 again watched the imbalance occur. QRH consulted as I'm thinking possible fuel leak as ALL engine parameters are dead on and aircraft is in trim. Decide to go back into the cabin myself and observe behind the left engine for any signs of a fuel leak. None observed. Back in the cockpit I have FO call MX control. Confer with MX and he checks history. Fuel gauge has a history and he is confident that it is a bad gauge. My only indication of a history is that which is my paperwork about the left gauge showing an error code when the fuel qty. test is done on preflight. At this time we are showing over a 1;000 lb imbalance. I disconnect the auto pilot again and check for any roll tendency or out of trim condition. None noted. CDU showing message 'using reserve fuel' and now showing arriving with 5.0 on the gas. With all information from MX we opt to continue. I had asked dispatch for WX for several divert airports. All were ok as far as WX goes. My dispatcher took it upon herself to ask the chief dispatcher to have ATC give us priority handling as they had planned to have us hold for several minutes at some point on the arrival. That step she took saved this flight from a much different outcome I feel. Normal descent and approach to visual approach. Short final below 500 ft I catch a glimpse of an amber caution light on the left aft fuel pump. Normal landing and taxi in. Asked line MX to have a mechanic come to the gate and meet with us. Left gauge 980 lbs; Right gauge 2650 lbs. Aft left pump light still illuminated. Showed this to the mechanic and asked if we could dip stick the left wing. We all went out and went to the number one drip stick nearest the wing root. As the drip stick extended to the max we could hear the float hit the bottom of the wing. The left gauge is accurate 980lbs in that wing at touchdown. Suggest we turn off the electric hydraulic pump in the left tank. Mechanic tells me he is familiar with this jet and issue. Looks at me and says 'I was afraid something like this would happen'. If we had held on descent I'm pretty sure this would have been a much different outcome. What about the previous flight if they had to go around or divert for WX? They thought they had landed with 7.7 on the gas. This has shaken my confidence in our MX department. With the 60 day history he had in front of him I wish MX control had come clean and said 'With what I'm seeing with this gauge being MEL'd recently and some other strange issues I don't have a lot of confidence in what this thing is telling you'. I would have diverted enroute if I had been given an honest assessment of this gauge. I will happy to discuss this with anyone if you need or want any different information other than what you see here.




Synopsis: A B737 Captain reported on an unreliable fuel quantity gauge; which had a history of problems but was reportedly operating normally. He was unknowingly landing in a low fuel situation; until he received low fuel pressure indications on short final.