Narrative:

The problem I encountered occurred on 3 revenue air carrier flts I dispatched on jul/xz/98. The flts in question were air carrier xyz, yyx, and xzz. The flts were operated under far part 121. The problem stems from a limitation of the aircraft being added due to an airworthiness directive on the aircraft (the brasilia E120), but not reflected in the MEL. An airworthiness directive was issued for the aircraft, and concerned a load-shedding problem with the electrical system when 1 generator was lost while the aircraft was in icing conditions and the deicing equipment was operating. The airworthiness directive required a modification of the aircraft, but allowed relief to operate the aircraft under certain limitations until the modifications could be made. Added to the limitations section of the aircraft's flight standards manual for unmodified aircraft was 'both starter/generators must operate normally prior to flight.' the MEL, however, was not updated, and under MEL allows for deferral of '1 generator function' provided some listed conditions were met. Maintenance deferred 1 generator prior to departure of flight xyz. The crew called me to advise me of the MEL added to the aircraft, and I consulted the MEL and determined that the deferral was a legal deferral, and all of the provisions were met. Only after the 3 revenue flts were completed was I made aware of the limitation of the aircraft which had been added as a temporary revision to the flight standards manual. Therefore, the flts were operated with an illegal deferral. The problem here obviously is the conflicting information between the flight standards manual and the MEL. As dispatchers, we refer to the MEL continuously to determine an aircraft's airworthiness for revenue part 121 operations. I believe that when a limitation is added to an aircraft, the MEL should be updated at the same time to reflect compliance with the limitation.

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Original NASA ASRS Text

Title: AN EMBRAER 120 WAS DISPATCHED WITH A GENERATOR SYS DEFERRED INOP PER THE MEL BUT IN CONFLICT WITH AN AIRWORTHINESS DIRECTIVE.

Narrative: THE PROB I ENCOUNTERED OCCURRED ON 3 REVENUE ACR FLTS I DISPATCHED ON JUL/XZ/98. THE FLTS IN QUESTION WERE ACR XYZ, YYX, AND XZZ. THE FLTS WERE OPERATED UNDER FAR PART 121. THE PROB STEMS FROM A LIMITATION OF THE ACFT BEING ADDED DUE TO AN AIRWORTHINESS DIRECTIVE ON THE ACFT (THE BRASILIA E120), BUT NOT REFLECTED IN THE MEL. AN AIRWORTHINESS DIRECTIVE WAS ISSUED FOR THE ACFT, AND CONCERNED A LOAD-SHEDDING PROB WITH THE ELECTRICAL SYS WHEN 1 GENERATOR WAS LOST WHILE THE ACFT WAS IN ICING CONDITIONS AND THE DEICING EQUIP WAS OPERATING. THE AIRWORTHINESS DIRECTIVE REQUIRED A MODIFICATION OF THE ACFT, BUT ALLOWED RELIEF TO OPERATE THE ACFT UNDER CERTAIN LIMITATIONS UNTIL THE MODIFICATIONS COULD BE MADE. ADDED TO THE LIMITATIONS SECTION OF THE ACFT'S FLT STANDARDS MANUAL FOR UNMODIFIED ACFT WAS 'BOTH STARTER/GENERATORS MUST OPERATE NORMALLY PRIOR TO FLT.' THE MEL, HOWEVER, WAS NOT UPDATED, AND UNDER MEL ALLOWS FOR DEFERRAL OF '1 GENERATOR FUNCTION' PROVIDED SOME LISTED CONDITIONS WERE MET. MAINT DEFERRED 1 GENERATOR PRIOR TO DEP OF FLT XYZ. THE CREW CALLED ME TO ADVISE ME OF THE MEL ADDED TO THE ACFT, AND I CONSULTED THE MEL AND DETERMINED THAT THE DEFERRAL WAS A LEGAL DEFERRAL, AND ALL OF THE PROVISIONS WERE MET. ONLY AFTER THE 3 REVENUE FLTS WERE COMPLETED WAS I MADE AWARE OF THE LIMITATION OF THE ACFT WHICH HAD BEEN ADDED AS A TEMPORARY REVISION TO THE FLT STANDARDS MANUAL. THEREFORE, THE FLTS WERE OPERATED WITH AN ILLEGAL DEFERRAL. THE PROB HERE OBVIOUSLY IS THE CONFLICTING INFO BTWN THE FLT STANDARDS MANUAL AND THE MEL. AS DISPATCHERS, WE REFER TO THE MEL CONTINUOUSLY TO DETERMINE AN ACFT'S AIRWORTHINESS FOR REVENUE PART 121 OPS. I BELIEVE THAT WHEN A LIMITATION IS ADDED TO AN ACFT, THE MEL SHOULD BE UPDATED AT THE SAME TIME TO REFLECT COMPLIANCE WITH THE LIMITATION.

Data retrieved from NASA's ASRS site as of July 2007 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.