Narrative:

I was the relief pilot on the flight. At the time of the discovery of the issue at hand; I was in the back of the aircraft on break. When I arrived on the flight deck the number 2 fuel tank showed 4;800 pounds; the number 1 tank at 12;800 [pounds] and [quantity] unknown on the number 3 tank; as it was dispatched with number 3 fuel tank indicator inoperative equals manual fuel procedures. After takeoff; all the appropriate procedures took place for manual fuel and monitored throughout the flight until the above occurrence. After coming to the flight deck; after being called up for a potential problem for fuel; the crew was running the fuel leak checklist for the number 2 tank and had number 2 isolated. I helped them finish the checklist and we had ascertained that number 2 did not have a fuel leak; but the fuel started increasing in the tank so we opened the cross-feeds [valves] to protect the engines and pressurize the manifold. At this point we felt that the actual fuel readings that we were seeing could be incorrect due to the fact that the fuel in number 1 and number 2 fuel tanks were very erratic; number 3 fuel [quantity] was unknown. We called company to advise [them] of the problem and we continued to work the fuel issue; there again not having any idea of what fuel quantity we had in number 3 tank; but up to that point felt that it equaled number 1's fuel quantity and number 2 continued to decrease. The fuel state [status] became critical for number 1 and number 2 fuel tanks and we elected to divert while talking to company and ATC center to ZZZ for fuel concerns due to a possible fuel leak which was directed by the checklist. We continued to work the fuel problem up to a safe landing in ZZZ1. We felt the tank quantities indications were possibly incorrect.

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Original NASA ASRS Text

Title: Three pilots describe their efforts to determine the actual fuel quantity on board an MD-11 aircraft during cruise flight after fuel indications in Number 1 and Number 2 Fuel Tanks became erratic while Number 3 Tank quantity was unknown due to being deferred 'inoperative.' Emergency was declared due to critical fuel status; aircraft diverted.

Narrative: I was the Relief Pilot on the flight. At the time of the discovery of the issue at hand; I was in the back of the aircraft on break. When I arrived on the Flight Deck the Number 2 Fuel Tank showed 4;800 LBS; the Number 1 Tank at 12;800 [LBS] and [quantity] unknown on the Number 3 Tank; as it was dispatched with Number 3 Fuel Tank Indicator inoperative equals Manual Fuel Procedures. After takeoff; all the appropriate procedures took place for Manual Fuel and monitored throughout the flight until the above occurrence. After coming to the Flight Deck; after being called up for a potential problem for fuel; the crew was running the Fuel Leak Checklist for the Number 2 Tank and had Number 2 isolated. I helped them finish the checklist and we had ascertained that Number 2 did not have a fuel leak; but the fuel started increasing in the tank so we opened the cross-feeds [valves] to protect the engines and pressurize the manifold. At this point we felt that the actual fuel readings that we were seeing could be incorrect due to the fact that the fuel in Number 1 and Number 2 fuel tanks were very erratic; Number 3 fuel [quantity] was unknown. We called Company to advise [them] of the problem and we continued to work the fuel issue; there again not having any idea of what fuel quantity we had in Number 3 tank; but up to that point felt that it equaled Number 1's fuel quantity and Number 2 continued to decrease. The fuel state [status] became critical for Number 1 and Number 2 fuel tanks and we elected to divert while talking to Company and ATC Center to ZZZ for fuel concerns due to a possible fuel leak which was directed by the checklist. We continued to work the fuel problem up to a safe landing in ZZZ1. We felt the tank quantities indications were possibly incorrect.

Data retrieved from NASA's ASRS site as of July 2013 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.