FOKKER F28 FLC OPERATED ACFT CONTRARY TO THE ACFT'S APPROVED MEL EQUIP LIST.

Narrative

THE CAPT AND I RECEIVED THE ACFT AT AN OUTSTATION WITH 2 MEL ITEMS ALREADY LISTED. THE PERTINENT ONE WAS THE ALT ALERTER. AS PART OF THE MEL PROCESS; IT WAS DEACTIVATED. DURING OUR ARR INTO SEA; WE BRIEFED A PRACTICE CAT II APCH FOR PROCEDURAL PRACTICE. AS PART OF THE APCH; WE COUPLED THE AUTOPLT TO THE ILS. JUST BEFORE THE MIDDLE MARKER; THE AUTOPLT WENT OFF LINE; BUT THE AUTOPLT OUT' LIGHT DID NOT FLASH AS IT SHOULD. AFTER AN UNEVENTFUL LNDG; THE CAPT CALLED MAINT AND WROTE UP THE AUTOPLT APCH FUNCTION IN THE MAINT LOG. BECAUSE IT WAS JUST THE APCH FUNCTION THAT WE THOUGHT WAS FAULTY; IT DID NOT SEEM TO CONFLICT WITH THE ALT ALERTER BEING ON THE MEL. WE THEN CONTINUED TO OUR NEXT DEST. NEARLY A WK LATER; AN ASSISTANT CHIEF PLT CALLED ASKING ABOUT THE INCIDENT. HE CLAIMED THAT BOTH ITEMS CANNOT BE ON THE MEL AT THE SAME TIME. MY SUGGESTION IS THAT FOR CONFLICTING MEL ITEMS LIKE THIS; THE PROCS SHOULD BE EXPLICIT REGARDING WHETHER THE AUTOPLT CAN STILL BE USED ENRTE IF IT FAILED ON AN APCH MODE. COMMON SENSE INDICATES THAT A NORMALLY OPERATING AUTOPLT WITH THE APCH FUNCTION DEFERRED IS NOT IN CONFLICT WITH THE ALT ALERTER INOP.