Narrative:

Incompatible MEL's were issued for a flight on a B737-400 aircraft. An airspeed indicator and an FMS computer were on MEL. Better verbiage on the MEL book would prevent this from happening again. Supplemental information from acn 344243: released flight with 2 conflicting MEL's. Conflict not recognized prior to departure (1 flight segment san-sea). The aircraft should never have been released by maintenance without correcting either one or the other of the 2 MEL's. The dispatcher (myself) should also have caught discrepancy, however, workload was a prime factor in not catching mistake. I might add, I released flight and was relieved of shift and went home prior to departure. I worked 'graveyard' shift and flight departed during day shift. Supplemental information from acn 344245: in the corrective action block of the maintenance page there was an en route MEL issued and signed, but no placards were installed. A phone call to maintenance control confirmed that the airspeed indicator was in fact on the MEL list, and I was to correctly placard the gauge and logbook. In the meantime, more than the normal amount of distrs had built up. Catering was inadequate, duplicate seating problems, and clearance delivery had problems issuing clrncs forcing us to refile. In all the confusion, somehow we missed the note on the FMC inoperative procedure that read, 'speed tape is not to be used as primary airspeed indication.' maybe we missed it because the speed tape and airspeed indicator actually did operate normally. One correction to the problem would be when an FMC is deemed inoperative, a placard should be added to the speed tape. Seeing a placard on the speed tape and the airspeed indicator would have made it obvious that we had a no-fly situation on paper. The FMC was inoperative due to a fuel total problem only. Speed tape worked fine -- the airspeed indicator problem was on the ground - - once only. Supplemental information from acn 344435: aircraft arrived at gate late. Crew deplaning briefed us on FMC, stating only fuel and VNAV portions of FMC not working. Looked up both MEL items as a crew but with some distrs, ie, maintenance checks flight attendant requests and normal cockpit duties. I missed putting both MEL's together. On second leg reviewed all MEL items, however, still did not put airspeed inoperative and FMC inoperative together for no-go. FMC was working in all functions except fuel calculations. I should have caught the problem with dispatcher or maintenance on first flight and not relied on crew getting off aircraft. Supplemental information from acn 344247: while there was no safety of flight issue, it appears that I should not have accepted the aircraft with these conflicting MEL's. I was the third crew to fly the aircraft with these MEL's. Because it came in with these MEL's I did not check the MEL book as I should have. Instead relying on the fact that dispatch and maintenance control had released the aircraft and 2 other crews had been flying it. The MEL system should be used to flag inoperative items for flcs and to create a record of what items need to be fixed. It also provides a safeguard against operating the aircraft in an unsafe condition. Frequently when an item breaks, maintenance is forced to assign an MEL that is very broad. In this case, the FMC -- which has numerous functions -- if any one becomes inoperative, the MEL only allows for the entire unit to be deemed inoperative. Even if 99 percent of the FMC works fine. This does not make sense. Why take away useful tools from the pilots for only the sake of a strict bureaucratic interpretation of how the MEL should be applied. No clear guidance is provided in the preamble as to whether operative portions may be used. Our autoplt MEL states that operative portions may be used. This language should be added to the FMC MEL. The MEL should be a useful tool and not a arbitrary document used to trip up pilots, mechanics, and dispatchers on technicalities.

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Original NASA ASRS Text

Title: B737-400 DISPATCHED ILLEGALLY WITH CERTAIN 'NO-GO' ITEMS ENTERED IN LOGBOOK. DISPATCHERS COMPLAIN OF AIRLINE MAINT DEPT FAILING TO ADHERE TO THE PRINCIPLES OF THE MEL REQUIREMENTS FOR A B737-400. RPT ALLUDES TO A PUB DEFICIENCY. SPLIT SHIFT FOR DISPATCHERS. SECOND DISPATCHER FAILS TO CATCH ERROR. 3 DIFFERENT FLCS ALSO FAIL TO CATCH THIS PAPER ERROR ON AN AIRWORTHY ACFT.

Narrative: INCOMPATIBLE MEL'S WERE ISSUED FOR A FLT ON A B737-400 ACFT. AN AIRSPD INDICATOR AND AN FMS COMPUTER WERE ON MEL. BETTER VERBIAGE ON THE MEL BOOK WOULD PREVENT THIS FROM HAPPENING AGAIN. SUPPLEMENTAL INFO FROM ACN 344243: RELEASED FLT WITH 2 CONFLICTING MEL'S. CONFLICT NOT RECOGNIZED PRIOR TO DEP (1 FLT SEGMENT SAN-SEA). THE ACFT SHOULD NEVER HAVE BEEN RELEASED BY MAINT WITHOUT CORRECTING EITHER ONE OR THE OTHER OF THE 2 MEL'S. THE DISPATCHER (MYSELF) SHOULD ALSO HAVE CAUGHT DISCREPANCY, HOWEVER, WORKLOAD WAS A PRIME FACTOR IN NOT CATCHING MISTAKE. I MIGHT ADD, I RELEASED FLT AND WAS RELIEVED OF SHIFT AND WENT HOME PRIOR TO DEP. I WORKED 'GRAVEYARD' SHIFT AND FLT DEPARTED DURING DAY SHIFT. SUPPLEMENTAL INFO FROM ACN 344245: IN THE CORRECTIVE ACTION BLOCK OF THE MAINT PAGE THERE WAS AN ENRTE MEL ISSUED AND SIGNED, BUT NO PLACARDS WERE INSTALLED. A PHONE CALL TO MAINT CTL CONFIRMED THAT THE AIRSPD INDICATOR WAS IN FACT ON THE MEL LIST, AND I WAS TO CORRECTLY PLACARD THE GAUGE AND LOGBOOK. IN THE MEANTIME, MORE THAN THE NORMAL AMOUNT OF DISTRS HAD BUILT UP. CATERING WAS INADEQUATE, DUPLICATE SEATING PROBS, AND CLRNC DELIVERY HAD PROBS ISSUING CLRNCS FORCING US TO REFILE. IN ALL THE CONFUSION, SOMEHOW WE MISSED THE NOTE ON THE FMC INOP PROC THAT READ, 'SPD TAPE IS NOT TO BE USED AS PRIMARY AIRSPD INDICATION.' MAYBE WE MISSED IT BECAUSE THE SPD TAPE AND AIRSPD INDICATOR ACTUALLY DID OPERATE NORMALLY. ONE CORRECTION TO THE PROB WOULD BE WHEN AN FMC IS DEEMED INOP, A PLACARD SHOULD BE ADDED TO THE SPD TAPE. SEEING A PLACARD ON THE SPD TAPE AND THE AIRSPD INDICATOR WOULD HAVE MADE IT OBVIOUS THAT WE HAD A NO-FLY SIT ON PAPER. THE FMC WAS INOP DUE TO A FUEL TOTAL PROB ONLY. SPD TAPE WORKED FINE -- THE AIRSPD INDICATOR PROB WAS ON THE GND - - ONCE ONLY. SUPPLEMENTAL INFO FROM ACN 344435: ACFT ARRIVED AT GATE LATE. CREW DEPLANING BRIEFED US ON FMC, STATING ONLY FUEL AND VNAV PORTIONS OF FMC NOT WORKING. LOOKED UP BOTH MEL ITEMS AS A CREW BUT WITH SOME DISTRS, IE, MAINT CHKS FLT ATTENDANT REQUESTS AND NORMAL COCKPIT DUTIES. I MISSED PUTTING BOTH MEL'S TOGETHER. ON SECOND LEG REVIEWED ALL MEL ITEMS, HOWEVER, STILL DID NOT PUT AIRSPD INOP AND FMC INOP TOGETHER FOR NO-GO. FMC WAS WORKING IN ALL FUNCTIONS EXCEPT FUEL CALCULATIONS. I SHOULD HAVE CAUGHT THE PROB WITH DISPATCHER OR MAINT ON FIRST FLT AND NOT RELIED ON CREW GETTING OFF ACFT. SUPPLEMENTAL INFO FROM ACN 344247: WHILE THERE WAS NO SAFETY OF FLT ISSUE, IT APPEARS THAT I SHOULD NOT HAVE ACCEPTED THE ACFT WITH THESE CONFLICTING MEL'S. I WAS THE THIRD CREW TO FLY THE ACFT WITH THESE MEL'S. BECAUSE IT CAME IN WITH THESE MEL'S I DID NOT CHK THE MEL BOOK AS I SHOULD HAVE. INSTEAD RELYING ON THE FACT THAT DISPATCH AND MAINT CTL HAD RELEASED THE ACFT AND 2 OTHER CREWS HAD BEEN FLYING IT. THE MEL SYS SHOULD BE USED TO FLAG INOP ITEMS FOR FLCS AND TO CREATE A RECORD OF WHAT ITEMS NEED TO BE FIXED. IT ALSO PROVIDES A SAFEGUARD AGAINST OPERATING THE ACFT IN AN UNSAFE CONDITION. FREQUENTLY WHEN AN ITEM BREAKS, MAINT IS FORCED TO ASSIGN AN MEL THAT IS VERY BROAD. IN THIS CASE, THE FMC -- WHICH HAS NUMEROUS FUNCTIONS -- IF ANY ONE BECOMES INOP, THE MEL ONLY ALLOWS FOR THE ENTIRE UNIT TO BE DEEMED INOP. EVEN IF 99 PERCENT OF THE FMC WORKS FINE. THIS DOES NOT MAKE SENSE. WHY TAKE AWAY USEFUL TOOLS FROM THE PLTS FOR ONLY THE SAKE OF A STRICT BUREAUCRATIC INTERP OF HOW THE MEL SHOULD BE APPLIED. NO CLR GUIDANCE IS PROVIDED IN THE PREAMBLE AS TO WHETHER OPERATIVE PORTIONS MAY BE USED. OUR AUTOPLT MEL STATES THAT OPERATIVE PORTIONS MAY BE USED. THIS LANGUAGE SHOULD BE ADDED TO THE FMC MEL. THE MEL SHOULD BE A USEFUL TOOL AND NOT A ARBITRARY DOCUMENT USED TO TRIP UP PLTS, MECHS, AND DISPATCHERS ON TECHNICALITIES.

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.