Date: 201207
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Fuel System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Relief Pilot
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Release Refused / Aircraft Not Accepted; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Procedure
Primary problem: Aircraft

Narrative: I served as the Relief Pilot for this flight. The trip started off with the aircraft was over fueled by 1;000 LBS by refueling personnel. A new Weight and Balance was obtained with the revised fuel weight and the flight departed uneventfully. The aircraft landed and refueled with no indications of a fuel system problem. Next leg was uneventful as well. While refueling ground personnel notified the pilots the aircraft was leaking something out of the left wing. I went to investigate while the Captain and First Officer remained in the cockpit. I observed fuel overflowing out the left wing at an extreme rate. I notified the Captain and at that same time refueling was terminated and the overflow condition ceased. I estimate 1;000-2;000 LBS were spilled. Clean up crews and Fire Department personnel began the clean up as we de-boarded the aircraft. The on board Mechanic began to troubleshoot the system. While troubleshooting; I along with the crew viewed fuel transferring from one wing to the other with the fuel valve switches closed. This was concerning due to the fact that if this occurred airborne the aircraft would become uncontrollable after 5-10 minutes due to the imbalance. The Captain and the mechanic went to Operations to call Maintenance after troubleshooting. I was present during the conversation with the Captain when he was discussing the issue with a Mechanic on the phone. The Captain explained that with this uncontrollable fuel transfer to one wing the aircraft would not be safe to fly until it was positively fixed. The discussion heated as the Captain said; 'He was not going to take the Mechanic's advice to go fly and see what happens airborne'. The conversation ended with the Captain explaining that the aircraft was not going to fly when he; the First Officer; the Relief Pilot and the on board Mechanic refuse to fly for safety.Following the phone call I talked with the Captain further about the phone call. He stated; the mechanic said this situation was not mechanically possible and the crew should take it flying and see what happens. He also told me the mechanic said; 'Pilots what if situations too much'. The Captain and First Officer then taxied the aircraft to a new parking spot. When they returned they stated the fuel once again transferred uncontrollably to one wing. Not one member of the crew wanted to lose a day and desired to have their full planned layover; but safety dictated that it was not safe to fly that aircraft until the mechanical situation was positively identified and resolved. The whole crew was placed in a hotel for the night until a rescue flight arrived the next day. At that point we took the new aircraft and the rescue crew took our aircraft after the plane's defuel valve was manually closed. Later I talked with two different on board mechanics. They said that the manual de-fueling handle broke open and that there was also a refueling valve that was broken. He also stated this aircraft had an issue prior to our flight. I have several safety concerns listed below as it relates to this situation. 1. There was no write up in the aircraft logbook about any such fuel system issue prior to our flight so there was no way a crew would know of such issues before they take the aircraft. 2. The over fueling of the aircraft initially may have been caused by the system actually being broken prior to the start of the flight and there are no procedures with refueling personnel to catch this problem.3. This issue could be occurring with our other aircraft in the fleet and there should be a fleet wide inspection of these system components.4. My last and greatest concern is with the Maintenance Supervisor who was on the call with the Captain and the potential lack of safety culture at the management level within the Maintenance Department. When the Captain states he is not comfortable to fly along with the entire crew to include the on board mechanic then those statements should be listened to.Pushing a crew to fly the aircraft and see what happens is not an environment that promotes safety first and could end with disastrous results. That type of culture will cause the airline to lose an aircraft and lives.




Synopsis: B737-800 First Officer discovers on third leg of his flight that the fuel system is malfunctioning; causing fuel spills and uncontrolled fuel transfer between wings. A Maintenance Supervisor suggests that this situation is not mechanically possible and the crew should take it flying and see what happens. The crew declines.