Narrative:

We were dispatched as a weight restr flight. We were at a lesser weight than the restr for takeoff, so we departed dfw. En route to cos, I pulled out the performance manual to calculate landing data at cos with snow on the runway. I did not look at flaps 25 degrees data, only flaps 42 degrees data, as I would not normally land on a wet runway at flaps 25 degrees. Data showed that with the engine anti-ice correction and the ice accretion calculations, our climb limited landing weight was 86300 pounds. I had my first officer calculate the data separately. His numbers were the same, I sent the data to dispatch via ACARS and burned down to the appropriate weight prior to landing. The dispatcher and I talked after landing and he was concerned that the original tps data did not specifically indicate that the takeoff weight restr was based on a planned flaps 25 degree landing. A more restrictive weight would have been associated with a planned flaps 42 degree landing. He is correct -- the possibility for the dispatcher to plan based on 1 specific constraint and the captain 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 landing flap configns would alleviate this miscom in the future.

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Original NASA ASRS Text

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

Narrative: 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.

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.