Narrative:

The following event occurred at the gate. Aircraft (E145/left) had an existing MEL for the APU starter-generator. Prior to departure; company maintenance control deferred the engine driven generator bearings for the #1 generator. A condition for an APU starter generator deferral is that all 4 engine driven generators must operate normally. I expressed my concern to the captain that these 2 MEL's might not be compatible. Maintenance control insisted that the #1 generator was operating normally and that MEL was deferrable. One of the bearings in generator 1 was worn but the generator was operating normal (voltage/amps). The captain consulted with a company flight manager who concurred with maintenance control. I was also persuaded by maintenance control. The captain and I added the new MEL to the dispatch release via 'pen and ink.' I am no longer confident that it was correct to defer both of those items. I believe the MEL language is too vague and should be clarified. What specifically does operate 'normally' mean? Maintenance's position was that the generator was doing everything it was supposed to and that the generator bearing MEL merely indicated that a bearing was worn and that the generator would need to be replaced 'prior' to a generator failure. I believe that the MEL language should be more specific. I should have been more conservative in my interpretation of the MEL. Supplemental information from acn 789744: the flight previous to this; we got a generator 1 bearing failure advisory message. We looked at the QRH for that and all it said was contact maintenance control when on the ground. We did; and they had us defer the generator 1 even though it was working. We then flew that aircraft on. The next day we discovered the crew that was to take our aircraft back to ZZZ the previous day refused to fly it because the APU generator was already deferred. The MEL says that if the APU generator is deferred; all other generators must work normally. This occurred because we (the flight crew); maintenance control; and flight control all agreed that we were legal to fly.

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Original NASA ASRS Text

Title: REPORT FROM DISPATCHER AND FO THAT EMB145 WAS DISPATCHED WITH APU AND ONE ENGINE DRIVEN GENERATOR DEFERRED; IN VIOLATION OF MEL RESTRICTIONS.

Narrative: THE FOLLOWING EVENT OCCURRED AT THE GATE. ACFT (E145/L) HAD AN EXISTING MEL FOR THE APU STARTER-GENERATOR. PRIOR TO DEP; COMPANY MAINT CTL DEFERRED THE ENG DRIVEN GENERATOR BEARINGS FOR THE #1 GENERATOR. A CONDITION FOR AN APU STARTER GENERATOR DEFERRAL IS THAT ALL 4 ENG DRIVEN GENERATORS MUST OPERATE NORMALLY. I EXPRESSED MY CONCERN TO THE CAPT THAT THESE 2 MEL'S MIGHT NOT BE COMPATIBLE. MAINT CTL INSISTED THAT THE #1 GENERATOR WAS OPERATING NORMALLY AND THAT MEL WAS DEFERRABLE. ONE OF THE BEARINGS IN GENERATOR 1 WAS WORN BUT THE GENERATOR WAS OPERATING NORMAL (VOLTAGE/AMPS). THE CAPT CONSULTED WITH A COMPANY FLT MGR WHO CONCURRED WITH MAINT CTL. I WAS ALSO PERSUADED BY MAINT CTL. THE CAPT AND I ADDED THE NEW MEL TO THE DISPATCH RELEASE VIA 'PEN AND INK.' I AM NO LONGER CONFIDENT THAT IT WAS CORRECT TO DEFER BOTH OF THOSE ITEMS. I BELIEVE THE MEL LANGUAGE IS TOO VAGUE AND SHOULD BE CLARIFIED. WHAT SPECIFICALLY DOES OPERATE 'NORMALLY' MEAN? MAINT'S POS WAS THAT THE GENERATOR WAS DOING EVERYTHING IT WAS SUPPOSED TO AND THAT THE GENERATOR BEARING MEL MERELY INDICATED THAT A BEARING WAS WORN AND THAT THE GENERATOR WOULD NEED TO BE REPLACED 'PRIOR' TO A GENERATOR FAILURE. I BELIEVE THAT THE MEL LANGUAGE SHOULD BE MORE SPECIFIC. I SHOULD HAVE BEEN MORE CONSERVATIVE IN MY INTERP OF THE MEL. SUPPLEMENTAL INFO FROM ACN 789744: THE FLT PREVIOUS TO THIS; WE GOT A GENERATOR 1 BEARING FAILURE ADVISORY MESSAGE. WE LOOKED AT THE QRH FOR THAT AND ALL IT SAID WAS CONTACT MAINT CTL WHEN ON THE GND. WE DID; AND THEY HAD US DEFER THE GENERATOR 1 EVEN THOUGH IT WAS WORKING. WE THEN FLEW THAT ACFT ON. THE NEXT DAY WE DISCOVERED THE CREW THAT WAS TO TAKE OUR ACFT BACK TO ZZZ THE PREVIOUS DAY REFUSED TO FLY IT BECAUSE THE APU GENERATOR WAS ALREADY DEFERRED. THE MEL SAYS THAT IF THE APU GENERATOR IS DEFERRED; ALL OTHER GENERATORS MUST WORK NORMALLY. THIS OCCURRED BECAUSE WE (THE FLT CREW); MAINT CTL; AND FLT CTL ALL AGREED THAT WE WERE LEGAL TO FLY.

Data retrieved from NASA's ASRS site as of May 2009 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.