Commercial Fixed Wing
Troubleshooting
Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Human Factors; MEL
During troubleshooting of the Left Fuel Quantity System; [the Maintenance Supervisor] said that the Fuel Quantity Left [Circuit Breaker] was pulled and collared. I then started with troubleshooting the system. We reset the breaker; then we opened the fueling door and the breaker did not pop. Then we closed the fueling door and disconnected the densitometer and the breaker popped. Then we removed the fuel quantity processor; and the breaker still popped. We opened the refueling door and the breaker would not reset. So then we replaced the breaker and tried everything over again. We opened the refueling door; and the breaker did not pop. We closed the refueling and disconnected the densitometer; but the breaker still popped. We removed the fuel processor and the breaker still popped. After a few hours of troubleshooting we still had the same problem that the aircraft came in with. [Since it was] the end of my shift; we put the aircraft in the configuration it came in without reading the MEL [Minimum Equipment List]. I briefly looked at the MEL [Minimum Equipment List] and did not recognize that there was an issue with the MEL. After reviewing the MEL; we found out that the fuel quantity breaker should be in and not collared and the densitometer connector should be capped and stowed; but the aircraft did not come in that way. From what I was told this morning; before the aircraft [was released] the connector was capped and stowed. We accomplished troubleshooting and found the faulty circuit that was causing the breaker popping. The circuit was isolated to comply with the MEL procedures. We will review every action of the MEL when work on a system that we come across.
During troubleshooting; the Maintenance technicians isolated the cause of the fuel quantity system fault; however due to time; they reconfigured the aircraft in the manner in which it arrived. Only after a thorough review of the Minimum Equipment List (MEL) did it become evident that the aircraft arrived in a state not in compliance with the MEL. The aircraft was configured per the MEL prior to departure.