WRONG ACFT WEIGHT AND BALANCE.

Narrative

AT SCHEDULED DEP FROM MIA TO MCO WE WERE GIVEN A COMPUTERIZED WT AND BAL AND THE CABIN DOOR WAS CLOSED FOR DEP. THE GND CREW WAS READY TO PUSH AND I COMPUTED THE TKOF PWR SETTING WHILE THE F/O COMPUTED THE STAB SETTING FROM THE INFO ON THE FORM. THIS WAS DONE HURRIEDLY TO DEPART ON SCHEDULE. THE NUMBERS WERE WITHIN LIMITS FOR THE AIRPLANE AND THE TKOF AND FLTS WERE NORMAL. APCHING MCO THE LNDG WT WAS COMPUTED AND THE ACFT WAS SLIGHTLY OVER LNDG WT. THIS SEEMED VERY ODD; BUT I STILL ASSUMED THE WTS WE WERE GIVEN WERE CORRECT. AFTER RECOMPUTING THE WTS (165 FOR EACH PAX RATHER THAN 170 WHICH IS ALLOWED FOR SUMMER) AND COUNTING INFANTS; I DECIDED THAT WE WERE GOING TO LAND RIGHT AT 71000 LBS (MAX GROSS LNDG WT). AFTER ARR AT THE GATE; I DECIDED THAT SINCE THE PAPERWORK STILL SHOWED US TO BE OVERWEIGHT I SHOULD WRITE UP AN OVERWT LNDG AND HAVE AN INSPECTION COMPLETED. THIS WAS DONE AND MAINT SIGNED OFF AN INSPECTION. SUBSEQUENTLY; I REALIZED THAT THE WT AND BAL PROVIDED BY THE MIA STATION WAS FOR ACFT XX RATHER THAN Y WHICH WE WERE FLYING. XX IS AN MLG A SERIES WITH HIGHER WT; WHILE Y IS A B SERIES. AFTER RUNNING A WT AND BAL FOR THE PROPER ACFT; WE WERE WELL UNDER LNDG WT; BUT ALL OF OUR PROVIDED DATA WAS INCORRECT. THERE PROBABLY WAS NOT A TRUE SAFETY PROB IN THIS CASE; AS WE WERE LIGHTER THAN THE WTS USED; BUT BECAUSE OF THE AMBIGUITY OF THE FORM IN USE BY THE COMPANY; IT WAS NOT IMMEDIATELY APPARENT THAT IT WAS FOR THE WRONG ACFT. ALL OF THE REMAINING PAPERWORK WAS FOR THE CORRECT ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATES ACFT WAS SUBSTITUTED PREVIOUS EVENING BUT NIGHT DISPATCH CREW NEGLECTED TO INFORM DAY DISPATCH CREW. INFO FOR ORIGINAL ACFT GIVEN TO FLT CREW. RPTR USED OPPORTUNITY TO SHOW DIRECTOR OF OPS THE FORMS USED BY HIS COMPANY BEFORE MERGER. MUCH BETTER ORGANIZED AND EASIER TO READ. INFO TAKEN TO TOP MGT.