Narrative:

After we were on the aircraft; we were informed that there was a pilot requesting our jumpseat. I looked at the tps at that time which showed that we were landing weight limited at 154.1L and our assumed takeoff weight was approximately 153.8 pounds. I said that it would be fine. I then met the pilot; and welcomed him aboard. During our before starting engines checklist; I looked at the fuel and commented that we were overfueled to 36.5 pounds (release fuel was 36.3 pounds). I mentioned at that time that we can call dispatch if need be and have him increase our en route fuel burn to accommodate the jumpseater. After we departed; I noticed that at our first waypoint ZZZ; we were approximately 7000 pounds less in the center tank. I pointed it out to first officer and the jumpseater at which point we discussed the situation. Once we were at cruising altitude; we accomplished the QRH procedure. I thought at that point we probably had the entire release fuel load; based on problems the fleet has been experiencing with fuel indication problems. Once the center tank burned down to zero; the mains would probably remain at full values and the rest would burn out of the center tank. The jumpseater also stated that if in fact we had the fuel on board that was indicated; after the center tanks burned down to zero; not only would we start burning out of the main tanks but also the fuel temperature would dramatically lower which would verify that indeed we did have zero in the center tanks. I called dispatch and informed them of our situation and that if the fuel load is accurate on board; we could not make ZZZ1 and need to divert into ZZZ2. He decided ZZZ2 would be better and he started getting things in motion. Not until the center tank burned down to zero and the fuel temperature did indeed drop that I made the decision to divert to ZZZ2. I felt that since all fuel burn computations were accurate after our initial findings; I did not declare an emergency. Landed at ZZZ2 without incident.

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Original NASA ASRS Text

Title: AN MD80 INDICATING THE PROPER FUEL LOAD WAS ACTUALLY UNDER FUELED 1100 GALLONS BECAUSE THE CTR FUEL TANK QUANTITY WAS IN ERROR.

Narrative: AFTER WE WERE ON THE ACFT; WE WERE INFORMED THAT THERE WAS A PLT REQUESTING OUR JUMPSEAT. I LOOKED AT THE TPS AT THAT TIME WHICH SHOWED THAT WE WERE LNDG WT LIMITED AT 154.1L AND OUR ASSUMED TKOF WT WAS APPROX 153.8 LBS. I SAID THAT IT WOULD BE FINE. I THEN MET THE PLT; AND WELCOMED HIM ABOARD. DURING OUR BEFORE STARTING ENGS CHKLIST; I LOOKED AT THE FUEL AND COMMENTED THAT WE WERE OVERFUELED TO 36.5 LBS (RELEASE FUEL WAS 36.3 LBS). I MENTIONED AT THAT TIME THAT WE CAN CALL DISPATCH IF NEED BE AND HAVE HIM INCREASE OUR ENRTE FUEL BURN TO ACCOMMODATE THE JUMPSEATER. AFTER WE DEPARTED; I NOTICED THAT AT OUR FIRST WAYPOINT ZZZ; WE WERE APPROX 7000 LBS LESS IN THE CTR TANK. I POINTED IT OUT TO FO AND THE JUMPSEATER AT WHICH POINT WE DISCUSSED THE SITUATION. ONCE WE WERE AT CRUISING ALT; WE ACCOMPLISHED THE QRH PROC. I THOUGHT AT THAT POINT WE PROBABLY HAD THE ENTIRE RELEASE FUEL LOAD; BASED ON PROBS THE FLEET HAS BEEN EXPERIENCING WITH FUEL INDICATION PROBS. ONCE THE CTR TANK BURNED DOWN TO ZERO; THE MAINS WOULD PROBABLY REMAIN AT FULL VALUES AND THE REST WOULD BURN OUT OF THE CTR TANK. THE JUMPSEATER ALSO STATED THAT IF IN FACT WE HAD THE FUEL ON BOARD THAT WAS INDICATED; AFTER THE CTR TANKS BURNED DOWN TO ZERO; NOT ONLY WOULD WE START BURNING OUT OF THE MAIN TANKS BUT ALSO THE FUEL TEMP WOULD DRAMATICALLY LOWER WHICH WOULD VERIFY THAT INDEED WE DID HAVE ZERO IN THE CTR TANKS. I CALLED DISPATCH AND INFORMED THEM OF OUR SITUATION AND THAT IF THE FUEL LOAD IS ACCURATE ON BOARD; WE COULD NOT MAKE ZZZ1 AND NEED TO DIVERT INTO ZZZ2. HE DECIDED ZZZ2 WOULD BE BETTER AND HE STARTED GETTING THINGS IN MOTION. NOT UNTIL THE CTR TANK BURNED DOWN TO ZERO AND THE FUEL TEMP DID INDEED DROP THAT I MADE THE DECISION TO DIVERT TO ZZZ2. I FELT THAT SINCE ALL FUEL BURN COMPUTATIONS WERE ACCURATE AFTER OUR INITIAL FINDINGS; I DID NOT DECLARE AN EMER. LANDED AT ZZZ2 WITHOUT INCIDENT.

Data retrieved from NASA's ASRS site as of January 2009 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.