Narrative:

While preparing for a part 135 flight from ZZZ to dtw, our company scheduling called to inform us that our aircraft was grounded for an unknown maintenance problem. We were told to continue preflting our challenger 604, just in case the problem was resolved in time to do the trip. At XA30, our passenger arrived. Scheduling informed us that we were 99% sure that we could do the trip, after the appropriate write-ups and deferrals were made. I was contacted by our maintenance control department. Maintenance control informed me that the mfd #2 was replaced recently with an improper part number. They contacted the manufacturer and apparently gained approval to defer the mfd #2 until the proper part number could be installed within the next 3 days. Maintenance control then told me 'word-for-word' how to write up and defer this item. I faxed them a copy of the write-up, and they agreed that everything was correct. By XA48, we were ready to depart, and successfully completed the flight. En route, I checked the MEL to verify my write-up and deferral, but could not find an entry for mfd deferrals. The MEL number given to me by maintenance control was a reference to ED1 and ED2 (EICAS display) deferrals. After landing, I called them, but they said that everything was correct. I assumed they had a special waiver from the manufacturer or the FAA, since there was also a reference to bombardier in the deferral. The next day we flew another 2 legs, ending at our home base. I spoke with one of our line mechanics, who was very knowledgeable about the CL604. He also believed that mfd's were not deferrable. I called maintenance control again, but again they said that the #2 mfd was deferrable. I met with our chief pilot tuesday morning to express my concerns (and distrust) for maintenance control. After further investigation, it turned out that I was correct, and I had let maintenance control talk me into making an inappropriate deferral. In my rush to complete the flight, I trusted their expertise to help me with the write-ups. But if I had taken the time to doublechk it, I may have caught their error.

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Original NASA ASRS Text

Title: CAPT OF CL60 SERIES ACFT LEARNS THAT HIS COMPANY MAINT PERSONNEL HAVE IMPROPERLY DEFERRED A MFD AND CONVINCED HIM TO MAKE AN INAPPROPRIATE LOGBOOK ENTRY VERIFYING THE CONDITION MET WITH THE APPROPRIATE MEL.

Narrative: WHILE PREPARING FOR A PART 135 FLT FROM ZZZ TO DTW, OUR COMPANY SCHEDULING CALLED TO INFORM US THAT OUR ACFT WAS GNDED FOR AN UNKNOWN MAINT PROB. WE WERE TOLD TO CONTINUE PREFLTING OUR CHALLENGER 604, JUST IN CASE THE PROB WAS RESOLVED IN TIME TO DO THE TRIP. AT XA30, OUR PAX ARRIVED. SCHEDULING INFORMED US THAT WE WERE 99% SURE THAT WE COULD DO THE TRIP, AFTER THE APPROPRIATE WRITE-UPS AND DEFERRALS WERE MADE. I WAS CONTACTED BY OUR MAINT CTL DEPT. MAINT CTL INFORMED ME THAT THE MFD #2 WAS REPLACED RECENTLY WITH AN IMPROPER PART NUMBER. THEY CONTACTED THE MANUFACTURER AND APPARENTLY GAINED APPROVAL TO DEFER THE MFD #2 UNTIL THE PROPER PART NUMBER COULD BE INSTALLED WITHIN THE NEXT 3 DAYS. MAINT CTL THEN TOLD ME 'WORD-FOR-WORD' HOW TO WRITE UP AND DEFER THIS ITEM. I FAXED THEM A COPY OF THE WRITE-UP, AND THEY AGREED THAT EVERYTHING WAS CORRECT. BY XA48, WE WERE READY TO DEPART, AND SUCCESSFULLY COMPLETED THE FLT. ENRTE, I CHKED THE MEL TO VERIFY MY WRITE-UP AND DEFERRAL, BUT COULD NOT FIND AN ENTRY FOR MFD DEFERRALS. THE MEL NUMBER GIVEN TO ME BY MAINT CTL WAS A REF TO ED1 AND ED2 (EICAS DISPLAY) DEFERRALS. AFTER LNDG, I CALLED THEM, BUT THEY SAID THAT EVERYTHING WAS CORRECT. I ASSUMED THEY HAD A SPECIAL WAIVER FROM THE MANUFACTURER OR THE FAA, SINCE THERE WAS ALSO A REF TO BOMBARDIER IN THE DEFERRAL. THE NEXT DAY WE FLEW ANOTHER 2 LEGS, ENDING AT OUR HOME BASE. I SPOKE WITH ONE OF OUR LINE MECHS, WHO WAS VERY KNOWLEDGEABLE ABOUT THE CL604. HE ALSO BELIEVED THAT MFD'S WERE NOT DEFERRABLE. I CALLED MAINT CTL AGAIN, BUT AGAIN THEY SAID THAT THE #2 MFD WAS DEFERRABLE. I MET WITH OUR CHIEF PLT TUESDAY MORNING TO EXPRESS MY CONCERNS (AND DISTRUST) FOR MAINT CTL. AFTER FURTHER INVESTIGATION, IT TURNED OUT THAT I WAS CORRECT, AND I HAD LET MAINT CTL TALK ME INTO MAKING AN INAPPROPRIATE DEFERRAL. IN MY RUSH TO COMPLETE THE FLT, I TRUSTED THEIR EXPERTISE TO HELP ME WITH THE WRITE-UPS. BUT IF I HAD TAKEN THE TIME TO DOUBLECHK IT, I MAY HAVE CAUGHT THEIR ERROR.

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.