AN FK100 FLC DEPARTS DFW OVERWT FOR THE FORTHCOMING LNDG ON A SET RWY AT COS; CO.

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WE WERE DISPATCHED AS A WT RESTR FLT. WE WERE AT A LESSER WT THAN THE RESTR FOR TKOF; SO WE DEPARTED DFW. ENRTE TO COS; I PULLED OUT THE PERFORMANCE MANUAL TO CALCULATE LNDG DATA AT COS WITH SNOW ON THE RWY. I DID NOT LOOK AT FLAPS 25 DEGS DATA; ONLY FLAPS 42 DEGS DATA; AS I WOULD NOT NORMALLY LAND ON A WET RWY AT FLAPS 25 DEGS. DATA SHOWED THAT WITH THE ENG ANTI-ICE CORRECTION AND THE ICE ACCRETION CALCULATIONS; OUR CLB LIMITED LNDG WT WAS 86300 LBS. I HAD MY FO CALCULATE THE DATA SEPARATELY. HIS NUMBERS WERE THE SAME; I SENT THE DATA TO DISPATCH VIA ACARS AND BURNED DOWN TO THE APPROPRIATE WT PRIOR TO LNDG. THE DISPATCHER AND I TALKED AFTER LNDG AND HE WAS CONCERNED THAT THE ORIGINAL TPS DATA DID NOT SPECIFICALLY INDICATE THAT THE TKOF WT RESTR WAS BASED ON A PLANNED FLAPS 25 DEG LNDG. A MORE RESTRICTIVE WT WOULD HAVE BEEN ASSOCIATED WITH A PLANNED FLAPS 42 DEG LNDG. HE IS CORRECT -- THE POSSIBILITY FOR THE DISPATCHER TO PLAN BASED ON 1 SPECIFIC CONSTRAINT AND THE CAPT TO EXECUTE THE PLAN USING A DIFFERENT CONSTRAINT DOES EXIST. UNLESS BOTH ARE AWARE OF AND PLANNING ON USING THE SAME PERFORMANCE VARIABLES IN THEIR CALCULATIONS A MISUNDERSTANDING COULD OCCUR. A SINGLE STATEMENT LINE ON THE TPS INDICATING THAT PERFORMANCE ASSUMPTIONS ARE BASED UPON SPECIFIC LNDG FLAP CONFIGNS WOULD ALLEVIATE THIS MISCOM IN THE FUTURE.