AN MD88 CAPT ACCEPTS HIS ACFT WITH A NON MEL'ED FMS THAT REFLECTED AN ENG MIX OF 2 DIFFERENT TYPES OF ENGS; AFFECTING THE COMPUTER READOUT FOR CORRECT FMS DATA.

Narrative

ON DEC/WED/99 I WAS PIC OF AN MD88 ACFT AND WENT FROM MKE TO LAX TO MKE. THE ACFT HAD RETURNED TO SVC ON DEC/TUE/99 AFTER AN ENG CHANGE. ON DEC/WED/99 THE ACFT HAD A MIXED ENG ARRANGEMENT (ONE 219 AND ONE 217 ENG). OUR FLT PLAN INFO AND TKOF PERFORMANCE INFO REFLECTED THE ENG MIX. UNFORTUNATELY; BOEING AND OUR MAINT DEPT DID NOT DEFER THE FMS ON BOARD THE ACFT OR UPDATE THE INFO IN THE FMS TO REFLECT THE ENG MIX. IT WAS BROUGHT TO MY ATTN THAT ON OR ABOUT DEC/FRI/99 THE FMS WAS DEFERRED. OUR COMPANY DOES NOT USE THE FMS FOR FUEL BURN; FUEL REMAINING; OR DRIFTDOWN CALCULATIONS. THESE ITEMS ARE COVERED IN OUR FLT PLAN DATA. AT THIS POINT IT DOES NOT APPEAR THAT ANY FAR WAS VIOLATED. WHAT DID OCCUR WAS THE USE OF THE FMS WITH INCORRECT DATA. IT WAS A MISTAKE BY NUMEROUS PEOPLE AND DEPTS. THE PROB HAS BEEN HANDLED BY THE DEFERRING OF THE FMS UNTIL THE ENGS CAN BE MATCHED. SUPPLEMENTAL INFO FROM ACN 458578: THE CAPT AND I PERFORMED THE RECEIVING CHKLIST AND NOTICED THAT THE TRP TESTED LIKE AN MD81/82 NOT AN MD88. HE INQUIRED WITH MAINT AND WAS TOLD THE ENGS HAD BEEN DERATED TO AN MD81/82 TYPE. WE NEVER VERIFIED THE CHANGE OF ENG MODELS IN THE FMS AND FLEW OUR FLT. NEITHER THE CAPT NOR I HAD EVER EXPERIENCED AN ENG DERATE SIT ON AN MD88 AND DIDN'T THINK TO CHK THE FMS IDENT PAGE FOR THE PROPER ENG MODEL NUMBER.