FLT CREW OF B744 EXPERIENCED TAIL STRIKE ON TKOF FROM RJNN. INCORRECT FUEL ON BOARD ENTERED INTO FMC RESULTED IN CALCULATED TKOF SPDS WELL UNDER THAT REQUIRED FOR ACTUAL TKOF GROSS WT.

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AT ROTATION ON TKOF IN NGO NOTICED A BUMP THAT FELT LIKE IT CAME FROM THE GEAR AREA. WE LOOKED AT THE EICAS GEAR SYNOPTIC PAGE TO SEE IF WE HAD BLOWN A TIRE ALONG WITH CHKING ALL OTHER SYS. EVERYTHING CHKED NORMAL. DURING THIS TIME WE GOT SEVERAL INSUFFICIENT FUEL MESSAGES; HOWEVER DISMISSED THEM BECAUSE THE WINDS HAD NOT BEEN COMPLETELY PROGRAMMED IN THE FMC. AFTER WE GOT TO ALT 33000 FT THE FO BROUGHT TO MY ATTN THAT PROGRESS PAGE 2 CALCULATED FUEL WAS COMING UP AT APPROX 68000 LBS AND NO TOTAL FUEL WAS INDICATED ON 6L PROGRESS PAGE 2. I SENT A MESSAGE TO DISPATCH AND MAINT CTL TO SEE IF THEY MIGHT HAVE AN IDEA HOW TO CORRECT THE PROB. SHORTLY AFTER WE DISCOVERED THE WRONG INFO ON THE CALCULATED FUEL BLOCK ON THE PERFORMANCE PAGE AND CORRECTED IT. THIS ALLEVIATED THE PROB. AT THIS POINT WE BECAME MORE CONCERNED ABOUT A POSSIBLE TAIL STRIKE; KNOWING OUR TKOF NUMBERS WERE WAY OFF. THE FO AND I DISCUSSED THIS AND WHAT ACTION; IF ANY; SHOULD BE TAKEN. AFTER CHKING ALL SYS THERE WERE STILL NO INDICATIONS OF ANYTHING ABNORMAL. AFTER DISCUSSING THIS WITH THE FO; I DECIDED TO WAKE THE CAPT; THE RELIEF PLT; TO GET HIS INPUT; WHICH WAS TO CONTINUE. I AGREED; THINKING THAT WE SIMPLY HAD HIT A BUMP ON THE RWY. AFTER ARRIVING IN DTW; WE INSPECTED THE TAIL SECTION AND CONFIRMED THERE HAD BEEN A TAIL STRIKE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED THAT THIS INCIDENT WAS THE SUBJECT OF AN INVESTIGATION BY THE ACR AND THE FAA. NO PROBABLE CAUSE SHORT OF A FINDING OF LIKELY PLT ERROR IN PROGRAMMING THE PERFORMANCE INITIALIZATION PAGE WAS REACHED. THE ASSUMPTION IS THAT SOMEHOW AN IMPROPER MANUAL ENTRY WAS MADE TO THE FUEL ON BOARD LINE OF THE PERFORMANCE INITIALIZATION PAGE WHICH OVERRODE THE AUTOMATIC FMC CALCULATION WHICH NORMALLY IS UTILIZED BY THE FMC FOR DEVELOPMENT OF THE TKOF V-SPDS. THE SPECIFICS OF HOW THIS OCCURRED WAS UNRESOLVED. THE RPTR AND THE ANALYST AGREED THE LACK OF AN INDEPENDENT CALCULATION METHOD FOR COMPARISON TO THE FMC DEVELOPED SPDS WAS INSTRUMENTAL IN ALLOWING THE ERROR TO GO UNDISCOVERED.