Narrative:

Originated in mht. Aircraft had #2 engine control unit meled. We read the MEL and were in compliance. En route to lga, #1 dc generator failed. Both yaw damper channels failed also after takeoff. Both items were written up in lga. Maintenance replaced #1 dc generator. The yaw damper was meled. We read the MEL for yaw damper and noted that autoplt cannot be used. After flying 3 legs, we were informed by maintenance in phl that we couldn't fly the airplane with both yaw dampers and an engine control unit inoperative. We remembered then, that the engine control unit MEL stated this, but we both forgot because at the time we read it, the yaw damper was working. The yaw damper MEL didn't mention both engine control units must be operating to be in compliance. I believe the problem was caused by us mentally thinking engine control unit MEL was in compliance because it was when we read it. With all that happened en route to lga, the MEL for the engine control unit was in the back of our heads. We didn't reread the engine control unit MEL to see if the yaw damper affected it. This was a mistake on our part. As a rule, we don't read the MEL items over before each flight unless it is a new MEL, which is what we did with the yaw damper. One problem that happened was the engine control unit MEL stated both yaw damper cannot be inoperative, however the yaw damper MEL didn't mention the engine control unit. It would help if mels included every possible item and system affected by it if inoperative, (ex, refer to engine control unit inoperative MEL) or company policy having us read mels prior to each flight.

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Original NASA ASRS Text

Title: DASH 8 FLC FAILED TO NOTICE THAT, WITH ENG CTL UNIT MELED THAT WITH BOTH YAW DAMPERS INOP, FLT WAS PROHIBITED.

Narrative: ORIGINATED IN MHT. ACFT HAD #2 ENG CTL UNIT MELED. WE READ THE MEL AND WERE IN COMPLIANCE. ENRTE TO LGA, #1 DC GENERATOR FAILED. BOTH YAW DAMPER CHANNELS FAILED ALSO AFTER TKOF. BOTH ITEMS WERE WRITTEN UP IN LGA. MAINT REPLACED #1 DC GENERATOR. THE YAW DAMPER WAS MELED. WE READ THE MEL FOR YAW DAMPER AND NOTED THAT AUTOPLT CANNOT BE USED. AFTER FLYING 3 LEGS, WE WERE INFORMED BY MAINT IN PHL THAT WE COULDN'T FLY THE AIRPLANE WITH BOTH YAW DAMPERS AND AN ENG CTL UNIT INOP. WE REMEMBERED THEN, THAT THE ENG CTL UNIT MEL STATED THIS, BUT WE BOTH FORGOT BECAUSE AT THE TIME WE READ IT, THE YAW DAMPER WAS WORKING. THE YAW DAMPER MEL DIDN'T MENTION BOTH ENG CTL UNITS MUST BE OPERATING TO BE IN COMPLIANCE. I BELIEVE THE PROB WAS CAUSED BY US MENTALLY THINKING ENG CTL UNIT MEL WAS IN COMPLIANCE BECAUSE IT WAS WHEN WE READ IT. WITH ALL THAT HAPPENED ENRTE TO LGA, THE MEL FOR THE ENG CTL UNIT WAS IN THE BACK OF OUR HEADS. WE DIDN'T REREAD THE ENG CTL UNIT MEL TO SEE IF THE YAW DAMPER AFFECTED IT. THIS WAS A MISTAKE ON OUR PART. AS A RULE, WE DON'T READ THE MEL ITEMS OVER BEFORE EACH FLT UNLESS IT IS A NEW MEL, WHICH IS WHAT WE DID WITH THE YAW DAMPER. ONE PROB THAT HAPPENED WAS THE ENG CTL UNIT MEL STATED BOTH YAW DAMPER CANNOT BE INOP, HOWEVER THE YAW DAMPER MEL DIDN'T MENTION THE ENG CTL UNIT. IT WOULD HELP IF MELS INCLUDED EVERY POSSIBLE ITEM AND SYS AFFECTED BY IT IF INOP, (EX, REFER TO ENG CTL UNIT INOP MEL) OR COMPANY POLICY HAVING US READ MELS PRIOR TO EACH FLT.

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.