COMPUTATION OF PAYLOAD IN KILOS VICE POUNDS RESULTS IN DC8 TAKING OFF AT A WT WELL ABOVE THAT COMPUTED. TAIL STRIKE ON DEP AND OVERWT LNDG AT DEST WERE RESULT.

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WE RECEIVED A CALL FROM LOAD PLANNING ON THE INTERPHONE THAT THERE MAY BE AN ISSUE WITH THE LOAD PLAN WTS. HE INFORMED US THAT THE WTS IN THE LOAD PLAN WERE IN KILOS NOT POUNDS! I PROMPTLY INFORMED THE REP THAT OUR PAPERWORK WAS DONE IN POUNDS NOT KILOS. I INFORMED HIM THAT I WANTED THE LOAD PLAN REVISED TO INDICATE ALL WTS IN POUNDS. THE REP LEFT AFTER MAKING SEVERAL PHONE CALLS. WE QUICKLY RECALCULATED AN APPROX TKOF WT AND FOUND ON ARR WE WOULD BE ABOVE OUR MAX LNDG WT OF 250000 LBS. OUR OPTIONS AT THIS POINT WERE AS FOLLOWS: HAVE THE CUSTOMER 'BUMP' FREIGHT; DE-FUEL THE ACFT OR PLAN A LOWER FLT ALT TO INCREASE OUR FUEL FLOW AND MAKE OUR LNDG WT SAFELY WITHIN LIMITS. AFTER DISCUSSING THIS WITH MY CREW AND MAINT; IT WAS MY DECISION NOT TO INCONVENIENCE THE CUSTOMER ANY MORE THAN HE HAD BEEN UP TO THIS POINT. MAINT INFORMED ME THAT DE-FUELING COULD TAKE A VERY LONG TIME SO I CALLED OPERATIONS AND HAD THEM RUN A FLT PLAN THAT WAS AT A LOWER ALT; TO MEET MY LNDG WT GOALS. UPON ARR AT THE ACFT WITH THE NEW LOAD PLAN; THE REP WAS VERY APOLOGETIC AND INFORMED ME THAT INDEED THE LOAD PLANNER HAD BEEN INFORMED TO CONVERT ALL WTS FROM KILOS TO POUNDS. HE ALSO INFORMED ME THAT THE PREVIOUS WEEK'S FLT; THE LOAD PLAN WAS ALSO DELIVERED WITH THE WTS IN KILOS! THIS BRINGS ME TO WHAT HAPPENED ON THE PREVIOUS WEEK'S FLT. ON ROTATION; THE FO STRUCK THE TAIL. I WAS LOOKING FORWARD AT THIS POINT BUT THE ROTATION DID NOT SEEM EXCESSIVE OR ABRUPT. WE AT FIRST THOUGHT WE MIGHT HAVE HAD A LOAD SHIFT; AS THERE WAS A VOID IN POSITION P-2; AND AFTER A SAFE ALT; WE CHKED THE LOAD AND IT APPEARED TO BE OK. WE HAD NO OTHER PROBLEMS WITH THE OPERATIONS OF THE ACFT SO THE DECISION WAS MADE TO CONTINUE TO OUR DEST. UPON MY ARR; AN ENGINEER AND MYSELF INSPECTED THE TAILSKID AND DETERMINED IT WAS WITHIN LIMITS DESCRIBED IN THE LIMITS SECTION. WE WROTE IT IN THE LOGBOOK AND DEPARTED WITHOUT INCIDENT. IN RETROSPECT OF THE ABOVE INCIDENT; WITH THE KNOWLEDGE FROM THE REP AS TO THE WTS BEING IN KILOS AND NOT POUNDS; IT IS MY CONCLUSION THAT THE ACFT WTS ON BOTH FLTS WERE APPROX THE SAME; NEARLY 285000 LBS AS OPPOSED TO THE 245000 LBS WE HAD COMPUTED OUR TAKEOFF NUMBERS FROM. AT A FLAPS 15 VR SPD OF AROUND 138 KTS; WE ROTATED OVER 10 KTS SLOW; AND THE ACTUAL CENTER GRAVITY OF THIS ACFT WAS AN UNKNOWN. AND THE ABOVE MENTIONED ACFT MAY HAVE HAD AN OVERWT LNDG ON ARR. I BELIEVE THERE WAS NO FAULT IN THE STRIKING OF THE TAIL OR THE OVERWT LNDG AS WE WERE FLYING THIS ACFT BASED ON INVALID DATA.