A Line Mechanic reports that after replacing the #2 Fuel Control and Monitoring Computer (FCMC-2) on an A330 aircraft; he wasn't aware that a 'Dummy' electrical connector plug and the locking plate for the horizontal stabilizer trim tank fuel inlet valve actuator also needed to be removed when he cleared the MEL.
Synopsis
A Line Mechanic reports that after replacing the #2 Fuel Control and Monitoring Computer (FCMC-2) on an A330 aircraft; he wasn't aware that a 'Dummy' electrical connector plug and the locking plate for the horizontal stabilizer trim tank fuel inlet valve actuator also needed to be removed when he cleared the MEL.
Narrative
I was assigned the task by my Lead to replace the Fuel Control and Monitoring Computer (FCMC-2) on an A330 aircraft due to [discrepancy] history. The aircraft was scheduled for Routine Over-Night (RON) maintenance and a work [paper] package was assigned. An MEL was written against the [horizontal stabilizer] trim tank inlet valve; but I wasn't aware that this was partly due to the FCMC. A [previous] MEL maintenance procedure (MP) to place [install] the trim tank inlet valve actuator locking plate was not reversed [removed] and a 'dummy' plug was not removed.There wasn't any indication that the [MEL] maintenance procedure had been complied with and the [FCMC] system tested OK. Another Aviation Maintenance Technician (AMT) that was more familiar with the pre-merger paperwork for that aircraft informed me that the item was written against an MEL. I did not see any MEL that involved the FCMC; but he told me that the MEL that was on the aircraft needed to be cleared since I changed out the FCMC. I cleared the MEL. I think what caused the problem was lack of clarity on what needed to be done and why; clarity on handling work packages; and also reading through the MEL. To prevent this from happening again I need to review the MEL maintenance procedures more closely. I corrected the situation by replacing the actuator and removing the locking plate and the dummy plug.
NASA callback
Reporter stated he has twenty-seven years experience working for two different airlines. The 'dummy' electrical connector plug was previously installed to give a 'normal' indication in the cockpit and ECAM displays; meaning no faults would show up even with the horizontal stab trim tank fuel actuator valve being locked and deferred in the 'Open' position with the locking plate. After changing the #2 Fuel Control and Monitoring Computer (FCMC-2); he did not remove the 'dummy' plug or fuel actuator valve locking plate from inside the tail section when he cleared the MEL.Reporter stated the FCMC controls all fuel functions on the aircraft including the rate of fuel going to the center fuel tanks from the horizontal stabilizer trim tank and the cycling of fuel back into the horizontal stab trim tank; in flight; to help maintain aircraft trim; weight and balance. He believes the FCMC was contributing to issues with the fuel transfer valves and the trim tank inlet valve actuator; so both items ended up being replaced.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.