B767-300 flight crew reported an increasing fuel imbalance in flight. The flight crew performed an in flight shut down of the left engine; and completed a diversion and landing.
Synopsis
B767-300 flight crew reported an increasing fuel imbalance in flight. The flight crew performed an in flight shut down of the left engine; and completed a diversion and landing.
Narrative
After level off at FL 380; Fuel Balance accomplished due to APU excessive run time for Block turn Back R GEN OFF MEL required APU run entire flight; After QRH Fuel Balance checklist was accomplished; fuel panel was in normal configuration. Fuel Config EICAS received at cruise a few minutes later; again verified fuel panel was in normal tank to engine and cross feed valves showed closed. Left Main Tank was reading approximately 8 thousand pounds Right Main Tank approximately 5 thousand pounds. Ran Fuel Config QRH; possible fuel leak; led to possible suspected fuel leak QRH; directed engine shutdown and land at nearest suitable airport. [Requested priority handling]; diverted to ZZZ. Landing made without incident; Crash Fire Rescue (CFR) inspected aircraft on runway; did not see external evidence of fuel leak; taxied to gate with CFR without further incident.Fuel quantities differed by significant amount; with Fuel Config EICAS.60 day Maintenance history showed 4 incidents of R SPAR valve not illuminating on Eng Shutdown; and a problem with right fueling panel load select. They may or may not be related.
Second reporter narrative
Top of climb actioned QRH to balance fuel due to 700 pounds imbalance due to maintenance issues prior to departure requiring a block turn back and extended APU use. Fuel was balanced using QRH to 8.3/8.2 in respective main tanks. QRH completed and all switches verified in correct position. Approximately 20-30 minutes later FUEL CONFIG EICAS and LIGHT displayed. Actioned QRH and verified fuel panel configured correctly. The fuel was reading approximately 8.5/4.5 in respective tanks. At this time Captain; as Pilot Monitoring; continued with QRH to determine cause of the imbalance and possible fuel leak. There was a minor difference between totalizer/calculated fuel of 200 pounds. At this point we discussed again if it was an imbalance or a fuel leak as directed by QRH. As there was such a large drop in the right main tank fuel quantity with the fuel panel configured correctly for phase of flight and fuel loading it was decided that attempting to balance fuel may exacerbate the situation and possibly lead to possible fuel starvation of the right engine. Captain; as pilot monitoring; proceeded to fuel leak checklist and it was decided that the appropriate action; per the fuel leak condition of large drop in fuel quantity in the right main tank; was to treat the condition as a fuel leak. Fuel Leak QRH procedure was actioned; including [request for priority handling] with ZZZ center and shutting down the right engine. A diversion to ZZZ was initiated and a jumpseating 767 Captain was utilized to assist in acquiring weather and notifying Dispatch of our intentions. We requested an ILS to Runway XX and accomplished a flap 20 landing. We remained on the runway and requested CFR to inspect the aircraft. After the inspection we taxied clear of the runway to the ramp and secured the aircraft per normal operations. After checklist was completed the Duty Officer was contacted.Ambiguity in QRH procedure regarding determining the cause of the imbalance and determining what the malfunction was specifically ie. a problem with a valve or an actual fuel leak.With the rate at which the fuel was decreasing in the right main tank was concerning and accurately determine the cause of the discrepancy through the QRH procedure was ambiguous.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.