Date: 201311
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: 5
Light: Night
Aircraft: MD-11
Operator: Air Carrier
Operating under: Part 121
Mission: Cargo / Freight / Delivery
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: Pilot Not Flying; Relief Pilot
Human factors: Troubleshooting; Confusion
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft; MEL; Manuals
Primary problem: Aircraft

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.


Second narrative: [We were] operating [City Pair] on an MD-11. Operating the Fuel System in Manual Mode due to a MEL; Number 3 [Fuel Tank] Indicator inoperative. We passed ZZZZ and made a fuel check and determined by manual procedures that we were 2;500 LBS above schedule. Looked at tank quantities and noted the Center Main Tank (Number 2) at 4;600 LBS. Initially reviewed the Manual Fuel Procedures (MFP) in the Aircraft Operating Manual to insure switches were in the correct positions. Immediately questioned and discussed the possibility of a fuel leak; ran the checklist and isolated the Number 2 Tank. We opened the cross-feeds [valves] to protect the running engines. With the Number 2 Tank isolated; the quantity in that tank increased and the Number 1 Tank was decreasing at a faster rate than we thought was normal. We assumed the Number 1 and Number 3 Tanks were together in quantity and to this point were operated in the same manner to keep those quantities the same. The quantity in the operating tanks were at levels lower than where we expected them to be; so we called Operations on the SAT phone to discuss our options. While talking to Maintenance and Dispatch; fuel in the operating tanks reached emergency level so I declared an emergency and diverted to ZZZ1. I flew the airplane and handled communications. My First Officer and Relief Pilot set up the approach. I elected to stay high on our descent into ZZZ1 in case of engine flameout. I joined the final on profile and noticed a lot of rudder was needed to maintain centerline. I questioned if we lost the Number 3 Engine and their response was no; all operating normally. Landed and parked with no other abnormalities.


Synopsis: 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.