Narrative:

On final for [an] ILS approach; passing 2;000 feet AGL; [we] received [a] fuel unbalance alert. Fuel synoptic showed approximately 9;000 lbs; 6;000 lbs; 4;500 lbs in main fuel tanks. Fuel quality in number 3 appeared to be rapidly decreasing (approximately 800 lbs/minute). I checked both the fuel synoptic and fuel system control panel; neither showed indications of transfer pumps; crossfeed valves; nor fill valves being on. [The] number 3 forward boost pump was deferred. Earlier on the arrival; I had reviewed the fuel synoptic and mentally noted a balanced fuel condition. During the approach; ATC advised of drone activity reported by previous aircraft; and we narrowly missed what appeared to be balloons passing thru 5;000 feet on final; which we reported to ATC. After receiving the alert; the first officer (first officer) and I discussed the situation; and decided the best course of action was to [advise ATC] and continue our approach; to [perform] an autoland; and then have ground personnel scan the airplane for indications of a fuel leak. The landing was uneventful; with no indications of lateral control issues. After exiting the runway; ground personnel scanned the airplane; and reported no evidence of a fuel leak; so we taxied to park.rapid fuel loss from number 3 (approximately 800 lbs/minute) combined with reported drone activity and observed balloon activity; contributed to our consideration of a potential fuel leak; and our decision to [advise ATC] and continue our approach to an immediate landing. I considered going missed approach to troubleshoot the alert; but we both felt that continuing the approach and landing was the safer course of action. After making the decision to land; I wanted the first officer to stay focused on his pm (pilot monitoring) duties; rather than running a QRH procedure; as we were within two minutes of touchdown.it's possible a malfunctioning channel of the fuel control unit caused the imbalance. Switching channels via the select/manual switch might have aided the situation. However; considering the variables present when the alert appeared; I think we took the safest course of action.

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Original NASA ASRS Text

Title: Air carrier Captain of a cargo aircraft reported the fuel in one of the wing tanks was decreasing much more rapidly that the other tanks.

Narrative: On final for [an] ILS approach; passing 2;000 feet AGL; [we] received [a] fuel unbalance alert. Fuel synoptic showed approximately 9;000 lbs; 6;000 lbs; 4;500 lbs in main fuel tanks. Fuel quality in Number 3 appeared to be rapidly decreasing (approximately 800 lbs/minute). I checked both the fuel synoptic and fuel system control panel; neither showed indications of transfer pumps; crossfeed valves; nor fill valves being on. [The] Number 3 forward boost pump was deferred. Earlier on the arrival; I had reviewed the fuel synoptic and mentally noted a balanced fuel condition. During the approach; ATC advised of drone activity reported by previous aircraft; and we narrowly missed what appeared to be balloons passing thru 5;000 feet on final; which we reported to ATC. After receiving the alert; the FO (First Officer) and I discussed the situation; and decided the best course of action was to [advise ATC] and continue our approach; to [perform] an autoland; and then have ground personnel scan the airplane for indications of a fuel leak. The landing was uneventful; with no indications of lateral control issues. After exiting the runway; ground personnel scanned the airplane; and reported no evidence of a fuel leak; so we taxied to park.Rapid fuel loss from Number 3 (approximately 800 lbs/minute) combined with reported drone activity and observed balloon activity; contributed to our consideration of a potential fuel leak; and our decision to [advise ATC] and continue our approach to an immediate landing. I considered going missed approach to troubleshoot the alert; but we both felt that continuing the approach and landing was the safer course of action. After making the decision to land; I wanted the FO to stay focused on his PM (Pilot Monitoring) duties; rather than running a QRH procedure; as we were within two minutes of touchdown.It's possible a malfunctioning channel of the fuel control unit caused the imbalance. Switching channels via the select/manual switch might have aided the situation. However; considering the variables present when the alert appeared; I think we took the safest course of action.

Data retrieved from NASA's ASRS site 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.