EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL
General None Reported / Taken
Aircraft; Procedure
We needed to write up a Gen 2 Off Bus EICAS message. I contacted Maintenance Control to perform the associated MEL. The aircraft had a previous MEL for Generator 1 Bearing. Maintenance and I talked about the two MELs together; about how there was no EICAS message stating that Gen 1 was off line or not operating correctly. The APU was not MEL'd; however; both active MELs state that there are four sources installed and three are needed for dispatch. The APU cannot count as one of the three; as it needs to be an Engine driven generator. So; even though Gen 1 was working correctly; there needed to be 3 working engine driven generators for each of the two MELs; which would require that one of the MEL'd generator would have to be considered as one of the three required sources.As the advance dispatch action it was just missed that the generator bearing function is really MEL-ing the entire generator. Maintenance; Dispatch and I all talked about the two MEL's; and we just missed it until the aircraft was in flight. The release should not have been amended; and the aircraft should not have been flown. While in flight I received ACARS messages from dispatch advising the aircraft should not have been released. Obviously looking back; I can't believe I missed the MEL section stating 'Engine' generators while reviewing both MEL's--the key word being 'Engine'--and the APU can not be considered as one of the three required for dispatch. I personally feel I needed to slow down the process.
An E-145 Captain; Dispatcher; and Maintenance Controller -- confused by conflicting deferrals on two engine driven generators; one of which was not 'deferred inoperative' -- determined erroneously that the aircraft could be released. Subsequent investigation determined that release was inappropriate as the generator with a 'deferred component in need of repair' could not qualify as an 'available generator' alternate electrical source for the 'deferred inoperative' one.