Narrative:

It was the first flight of the day and we showed up at the aircraft 40 mins prior to push. The aircraft was carrying an MEL item from the day before the flight. The MEL was the flight deck door access system keypad was inoperative (MEL 52-17). The MEL said we were good as long as we had an operating crew interphone system. We proceeded with our respective preflight duties and the 'a' flight attendant notified us of a problem that her crew interphone system was not working. Upon further examination, we discovered her PA system worked but her crew interphone did not. The 'B' flight attendant interphone and PA system worked normally and so did ours in the cockpit. The captain called dispatch and got maintenance on the line and informed maintenance and dispatch of our problem. Maintenance gave the captain 'MEL 23-4' with a tracking number for the forward flight attendant crew interphone not working. Dispatch followed with his initials and the time. The captain returned to the cockpit and he reviewed MEL 23-4 on the opc. It looked like we were good to go because upon glancing at the original MEL 52-17, we initially felt that since the cockpit and the 'B' flight attendant crew interphone worked fine, we had an operating system. Also, with dispatch and maintenance being in the loop, we thought we were good to go. While en route to ZZZ1 we reviewed the MEL again. Upon review of the MEL's, we questioned our interpretation of the system operating normally and decided that when we land, the captain would call dispatch and maintenance again and ask for a clarification and ruling on this point. Upon arriving, the next leg's paperwork showed both MEL's but the captain still called dispatch and maintenance that this MEL combination was in fact ok and not an oversight on their part and not a misinterp from ourselves. The captain told me when he called maintenance about the problem, that the maintenance person had to ask another maintenance person and together they realized it was not a legal combination for us to go with. So at this point we got contract maintenance in ZZZ1 to fix the 'a' flight attendant crew interphone. Unfortunately, maintenance missed the illegal MEL combination as well as dispatch and we initially misinterped the crew interphone MEL. (So we, too, initially missed it.)

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Original NASA ASRS Text

Title: A B737-300 WAS DISPATCHED IN NON COMPLIANCE WITH THE COCKPIT DOOR ACCESS KEYPAD DEFERRED PER THE MEL. FOUND FORWARD CABIN ATTENDANT'S CREW INTERPHONE INOP. ITEM WAS DEFERRED IN CONFLICT WITH THE MEL.

Narrative: IT WAS THE FIRST FLT OF THE DAY AND WE SHOWED UP AT THE ACFT 40 MINS PRIOR TO PUSH. THE ACFT WAS CARRYING AN MEL ITEM FROM THE DAY BEFORE THE FLT. THE MEL WAS THE FLT DECK DOOR ACCESS SYS KEYPAD WAS INOP (MEL 52-17). THE MEL SAID WE WERE GOOD AS LONG AS WE HAD AN OPERATING CREW INTERPHONE SYS. WE PROCEEDED WITH OUR RESPECTIVE PREFLT DUTIES AND THE 'A' FLT ATTENDANT NOTIFIED US OF A PROB THAT HER CREW INTERPHONE SYS WAS NOT WORKING. UPON FURTHER EXAM, WE DISCOVERED HER PA SYS WORKED BUT HER CREW INTERPHONE DID NOT. THE 'B' FLT ATTENDANT INTERPHONE AND PA SYS WORKED NORMALLY AND SO DID OURS IN THE COCKPIT. THE CAPT CALLED DISPATCH AND GOT MAINT ON THE LINE AND INFORMED MAINT AND DISPATCH OF OUR PROB. MAINT GAVE THE CAPT 'MEL 23-4' WITH A TRACKING NUMBER FOR THE FORWARD FLT ATTENDANT CREW INTERPHONE NOT WORKING. DISPATCH FOLLOWED WITH HIS INITIALS AND THE TIME. THE CAPT RETURNED TO THE COCKPIT AND HE REVIEWED MEL 23-4 ON THE OPC. IT LOOKED LIKE WE WERE GOOD TO GO BECAUSE UPON GLANCING AT THE ORIGINAL MEL 52-17, WE INITIALLY FELT THAT SINCE THE COCKPIT AND THE 'B' FLT ATTENDANT CREW INTERPHONE WORKED FINE, WE HAD AN OPERATING SYS. ALSO, WITH DISPATCH AND MAINT BEING IN THE LOOP, WE THOUGHT WE WERE GOOD TO GO. WHILE ENRTE TO ZZZ1 WE REVIEWED THE MEL AGAIN. UPON REVIEW OF THE MEL'S, WE QUESTIONED OUR INTERP OF THE SYS OPERATING NORMALLY AND DECIDED THAT WHEN WE LAND, THE CAPT WOULD CALL DISPATCH AND MAINT AGAIN AND ASK FOR A CLARIFICATION AND RULING ON THIS POINT. UPON ARRIVING, THE NEXT LEG'S PAPERWORK SHOWED BOTH MEL'S BUT THE CAPT STILL CALLED DISPATCH AND MAINT THAT THIS MEL COMBINATION WAS IN FACT OK AND NOT AN OVERSIGHT ON THEIR PART AND NOT A MISINTERP FROM OURSELVES. THE CAPT TOLD ME WHEN HE CALLED MAINT ABOUT THE PROB, THAT THE MAINT PERSON HAD TO ASK ANOTHER MAINT PERSON AND TOGETHER THEY REALIZED IT WAS NOT A LEGAL COMBINATION FOR US TO GO WITH. SO AT THIS POINT WE GOT CONTRACT MAINT IN ZZZ1 TO FIX THE 'A' FLT ATTENDANT CREW INTERPHONE. UNFORTUNATELY, MAINT MISSED THE ILLEGAL MEL COMBINATION AS WELL AS DISPATCH AND WE INITIALLY MISINTERPED THE CREW INTERPHONE MEL. (SO WE, TOO, INITIALLY MISSED IT.)

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.