B747-400 CREW TAXIED OFF THE HARD SURFACE WHEN THE TWR CTLR TOLD THE CREW TO USE THE REVERSE HIGH SPD TXWY.

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DURING FLT PREPARATION; THE CAPT; DISPATCH; AND I REVIEWED THE WX; NOTAMS; FUEL LOAD; AND AIRPLANE MAINT STATUS FOR THE FLT XXXX FROM IAD TO ZZZ. WE DISCUSSED THE ZZZ RWY 17 LNDG NOTAM AND REVIEWED IT IN CONJUNCTION WITH AN AVAILABLE ARPT DIAGRAM. WE BOTH AGREED THAT RWY 35 AT ZZZ WOULD BE THE PREFERRED LNDG RWY AND IT APPEARED THE FORECAST CONDITIONS UPON OUR ARR WOULD ALLOW US TO USE RWY 35 FOR LNDG. WE ALSO NOTED THE AUTO-SPDBRAKE DEFERRAL ON THE AIRPLANE. UPON ARR AT ZZZ; ACTUAL WIND CONDITIONS COMBINED WITH THE PERFORMANCE LIMITATIONS IMPOSED BY THE AUTO-SPDBRAKE DEFERRAL MADE A LNDG ON RWY 17 OUR ONLY LEGAL OPTION AT OUR 599000 LB LNDG WT. DURING THE APCH BRIEFING; WE REVIEWED THE NOTAM'S DIRECTIONS FOR EXECUTING A 180 DEG TURN AROUND AT THE S END OF RWY 17 AND TXWY A. WE ALSO KNEW (PER THE NOTAM) THAT WE WERE NOT SUPPOSED TO USE TXWY A S OF THE RAMP FOR CONCRETE STRESS REASONS. THE MINIMUM 180 DEG TURN RADIUS OF THE B747-400 IS 153 FT AND RWY 17/35 AT ZZZ IS ONLY 150 FT. AFTER A NORMAL APCH; LNDG; AND TAXI TO THE S END OF RWY 17; THE CAPT MANEUVERED THE AIRPLANE TO THE FAR R SIDE OF THE RWY TO EXECUTE A L 180 DEGS USING TXWY A FOR ADDITIONAL WIDTH DURING THE TURN. AFTER TURNING APPROX 90 DEGS TO THE L; IT BECAME APPARENT THAT WE WOULD NOT BE ABLE TO COMPLETE THE TURN AND STAY ON THE PAVEMENT. I VOICED MY CONCERN ABOUT THIS TO THE CAPT AND WE SLOWED TO A STOP FACING EASTWARD TOWARDS TXWY A. I RADIOED THE TWR ABOUT OUR PREDICAMENT. TWR INSTRUCTED US TO TAXI N ON TXWY A THEN TURN L ON TXWY B THEN BACK TO THE R ON RWY 17/35 TO TAXI TO THE RAMP. WE QUESTIONED THE TWR'S INSTRUCTIONS TO US IN REGARDS TO THE NOTAM. THE TWR ASSURED US IT WAS OK TO PROCEED UP TXWY A TO TXWY B BUT NOT TO GO BEYOND THE TXWY B ON TXWY A AS THE TXWY WASN'T STRESSED ENOUGH FURTHER UP. THE L TURN FROM TXWY A TO TXWY B APPEARED TO EXCEED 90 DEGS (APPEARS TO BE ABOUT 110-120 DEGS) ACCORDING TO THE TAXI CHART. I VOICED TWICE THAT THE UPCOMING TURN ONTO TXWY B WAS GOING TO BE 'PRETTY TIGHT.' THE CAPT LINED UP TO THE R SIDE OF TXWY A TO GIVE HIM MORE ROOM FOR THE TURN. HALFWAY THROUGH THE TURN; I FELT THE AIRPLANE SMOOTHLY AND EVER SO SLOWLY TILT SLIGHTLY LEFT THE RETURN TO WHERE IT WAS. I REALIZED THAT AT LEAST A FEW TIRES PROBABLY LEFT THE PAVEMENT. WHEN WE COMPLETED THE TURN N ON RWY 17/35; I COULD SEE 2 TIRE TRACKS ON THE INSIDE OF THE TXWY A TO TXWY B TURN AND REALIZED THE L WING GEAR HAD IN FACT BRIEFLY LEFT THE PAVEMENT. WHEN I INSPECTED THE AIRPLANE AFTER PARKING; THERE WAS SOME DRIED DIRT RESIDUE ON ALL 4 L WING GEAR TIRES. THERE WAS NO DIRT ON ANY OTHER PART OF THE L WING TRUCK AND THERE APPEARED TO BE NO DAMAGE TO EITHER THE L WING GEAR TRUCK OR TIRES. THE ONLY CONTRIBUTING FACTOR THAT MAY HAVE UNCONSCIOUSLY COME INTO PLAY WAS THE DESIRE TO COMPLETE THE MISSION. WE WERE RETURNING APPROX 310 SOLDIERS FROM 9 MONTHS OF DUTY IN IRAQ TO THEIR HOME AND MANY FRIENDS AND FAMILY WERE ANXIOUSLY WAITING OUTSIDE THE FENCE AT THE RAMP. SUPPLEMENTAL INFO FROM ACN 599983: WIND AT 150 DEGS/10 KTS MAKING RWY 35 UNUSABLE FOR LNDG. RWY 17 VISUAL APCH WAS NORMAL WITH LNDG IN THE TOUCHDOWN ZONE AND MANUAL SPDBRAKE DEPLOYMENT. ACFT WAS SLOWED TO BEGIN 180 DEG TURN ON THE RWY TO TAXI BACK FOR PARKING. AFTER APPROX 110 DEGS OF TURN; IT DID NOT APPEAR THE ACFT COULD COMPLETE THE TURN ON THE HARD SURFACE. THE FO CALLED THE TWR FOR INSTRUCTIONS. TWR ADVISED TURNOFF AND TAXI N ON TXWY A TO TXWY B TO REENTER THE RWY; AS N OF TXWY B WAS UNSATISFACTORY FOR B747 OPS. THE CREW QUERIED TWR AS THAT INSTRUCTION WAS CONTRARY TO THE NOTAM AND WE WERE ADVISED IT WAS OK. TXWY B REQUIRED APPROX 120 DEG TURN. AFTER THE TURN ONTO TXWY B; THE CAPT REENTERED THE RWY TO TAXI BACK TO TXWY E AND PARKING. BOTH CREW MEMBERS LOOKED OVER AND SAW TIRE TRACKS IN THE GRASS AT THE INTXN OF TXWYS A AND B. CAPT NOTIFIED DISPATCH WHO LET ZZZ TWR PERSONNEL KNOW OF THE DEP FROM THE TXWY. CAPT ALSO TALKED TO THE DUTY FLT MGR. MECH ON BOARD INSPECTED THE L MAIN WING GEAR AND FOUND NO DEFECTS EXCEPT SOME DIRTON THE TIRE SIDEWALLS. EVENTUALLY THE ORD CHIEF PLT ADVISED THE CREW TO SPEND THE NIGHT UNTIL A SAFETY DEBRIEFING WAS ACCOMPLISHED. ZZZ FIELD CONDITIONS WERE DRY AND THE GRASS SURFACES WERE HARD AND DRY.