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Air carrier flight crew reported a fuel system tank anomaly causing fuel to become trapped and unusable and necessitating an immediate diversion.
| Attributes | |
| ACN | 1572121 |
| Time | |
| Date | 201808 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | Widebody Transport |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Fuel Tank |
| Person 1 | |
| Function | Pilot Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Person 2 | |
| Function | Pilot Not Flying First Officer |
| Qualification | Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Inflight Event / Encounter Fuel Issue |
Narrative:
While at cruise FL360 received a 'tank 3 pumps off' alert. Consulted QRH which stated that the alert could be considered normal if fuel was less than 10;500 pounds in tanks 1 or 3 because of tip fuel transfer balancing. Crew then received alert 'tnk 3 tip trapped'; followed by a 'tank 3 qty low' alert. Tank 3 fuel quantity showed 7;000 lbs. Consulted QRH which said that tip fuel (5800 lbs.) was trapped and unusable. This put us in a possible emergency fuel state. Our destination was 160 miles away and closest suitable was ZZZ which was 50 miles away. [Operations control] and [maintenance control] were consulted and decision was made to divert to ZZZ. [ATC was notified about] the low fuel situation. An uneventful approach and landing was accomplished. Landed with 14;000 on fuel gauges and estimated 8;500 with the trapped fuel deducted.the number 3 tip tank that contains roughly 5;800 lbs of fuel did not drain into main tank as it normally should. Thus becoming fuel that is unusable. There is no crew action or QRH procedure for crew to perform to correct this. Usually caused by a stuck float/valve switch in tank.
Original NASA ASRS Text
Title: Air carrier flight crew reported a fuel system tank anomaly causing fuel to become trapped and unusable and necessitating an immediate diversion.
Narrative: While at cruise FL360 received a 'tank 3 pumps off' alert. Consulted QRH which stated that the alert could be considered normal if fuel was less than 10;500 pounds in tanks 1 or 3 because of tip fuel transfer balancing. Crew then received alert 'TNK 3 tip trapped'; followed by a 'Tank 3 QTY low' alert. Tank 3 fuel quantity showed 7;000 lbs. Consulted QRH which said that tip fuel (5800 lbs.) was trapped and unusable. This put us in a possible emergency fuel state. Our destination was 160 miles away and closest suitable was ZZZ which was 50 miles away. [Operations Control] and [Maintenance Control] were consulted and decision was made to divert to ZZZ. [ATC was notified about] the low fuel situation. An uneventful approach and landing was accomplished. Landed with 14;000 on fuel gauges and estimated 8;500 with the trapped fuel deducted.The Number 3 tip tank that contains roughly 5;800 lbs of fuel did not drain into main tank as it normally should. Thus becoming fuel that is unusable. There is no crew action or QRH procedure for crew to perform to correct this. Usually caused by a stuck float/valve switch in tank.
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.