B747-400 CAPTAIN REPORTS SUBSTANDARD TAKEOFF PERFORMANCE ON MILITARY CHARTER FLIGHT.

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THIS WAS A MILITARY CHARTER. WE EXPERIENCED SEVERAL PROBLEMS AND SAFETY ISSUES AS DESCRIBED BELOW: AIRCRAFT PERFORMED AS IF IT WAS OVERWEIGHT. WE ROTATED APPROXIMATELY 9;000 FT DOWN THE RUNWAY; MUCH FURTHER DOWN THAN I WOULD HAVE EXPECTED. TAKEOFF GROSS WEIGHT WAS APPROXIMATELY 805.0. MAXIMUM TAKEOFF GROSS WEIGHT WAS 858.0. WE USED MAXIMUM EPR AND FLAPS 20 DEGREES. THE RUNWAY WAS WET AND UNGROOVED. TEMPERATURE WAS 3 DEGREES CELSIUS AND WIND WAS APPROXIMATELY A 5 KT HEADWIND. WE WERE SURPRISED BY THE LENGTH OF THE TAKEOFF ROLL. I WAS STARTLED TO SEE THE DISPLACED THRESHOLD LINE QUICKLY APPROACHING. WE ROTATED OVER THAT LINE. ALSO; ON APPROACH TO ZZZ; THE CLEAN MANEUVERING BUG WAS RESTING ON THE YELLOW SPEED ARC; SIGNIFYING TO ME THAT THE AIRCRAFT THOUGHT IT WAS HEAVIER THAN WHAT WAS PROGRAMMED INTO THE FMC. I AM CONCERNED THAT THE WEIGHTS WE USED WERE INCORRECT; AND THAT WE WERE MUCH HEAVIER THAN WE THOUGHT. I FREQUENTLY FLY TO VHHH WITH HEAVIER WEIGHTS USING REDUCED POWER AND WARMER TEMPERATURES AND SEE MUCH BETTER PERFORMANCE THAN WHAT WE EXPERIENCED HERE. POSSIBLY; THE WEIGHTS USED PER PASSENGER ARE INCORRECT. THESE SOLDIERS WERE ALL HEAVILY LADEN WITH BACKPACKS AND GUNS; ETC. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING INFORMATION: REPORTER ADVISED THE FLIGHT CREW FAILED TO NOTE THE DISPLACED THRESHOLD NORTHEAST OF INTERSECTION F WHERE THEY ENTERED RUNWAY 21. THE ROTATION AT THE DISPLACED THRESHOLD AT THE FAR END WAS STILL 3;461 FT FROM THE PHYSICAL THRESHOLD OF THE RUNWAY. THIS GAVE THE IMPRESSION THAT THE ROTATION POINT WAS MORE DELAYED THAN; IN ACTUALITY; IT WAS. THIS ERROR DID NOT; HOWEVER; MITIGATE THE SUPPORTING EVIDENCE OF GREATER THAN PLANNED WEIGHT THAT CAME TO LIGHT WHEN MANEUVERING FOR LANDING. THE REPORTER ADVISES THE YELLOW ARC TO WHICH HE REFERS IS DERIVED DIRECTLY FROM ANGLE OF ATTACK INFORMATION THAT IS NOT INFLUENCED BY DATA ENTERED INTO THE FMS. THE CONTRADICTION BETWEEN THE ADVERTISED WEIGHT AND ACTUAL IS; THEREFORE; STILL WELL DOCUMENTED.