B747-400 CAPTAIN ADVISES UNABLE TO ACCESS FULL LENGTH OF RWY 10L FROM S2 TXWY AT SFO. BELIEVES REDUCED THRUST COMPUTATIONS BASED ON FULL LENGTH ARE NOT ACCURATE.

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THERE IS A POTENTIAL PROB WITH THE USE OF TXWY S2 TO ENTER SFO RWY 10L FOR TKOF. THE WESTERNMOST PORTION OF THE BULBOUS AREA OF S-S2 JUST TO THE S OF RWY 10L IS NOT AVAILABLE FOR TAXI. THEREFORE; THE CLOSEST A B747-400 CAN GET TO THE END OF THE RWY FOR TKOF LINE-UP IS APPROX 500 FT DOWN THE RWY. WE HAVE TKOF DATA AVAILABLE FROM THE FULL LENGTH OF RWY 10L AND FROM TXWY U WITH 10840 FT AVAILABLE; BUT NONE FROM 500 FT DOWN THE RWY. WHEN A FULLY LOADED B747-400 TAKES OFF IT WOULD BE PRUDENT TO KNOW IF THERE WAS ANY DIFFERENCE IN THE RWY PERFORMANCE DATA AT THESE 3 POINTS. ACCESS FROM TXWY S FROM THE N OR THE S TO RWY 10L ALLOWS FULL LENGTH USE AND TXWY U HAS SPECIFIC DATA; BUT NONE WAS AVAILABLE FOR ENTRY FROM TXWY S2. THE REPORTER ADVISED THEY UTILIZED MAX TKOF THRUST FOR THEIR DEPARTURE VICE THE NORMAL REDUCED FIGURE BASED; THEY BELIEVED; ON THE FULL LENGTH OF THE RWY. HIS ACR'S TECH SPECIALISTS HAVE SINCE ADVISED THEY WERE AWARE OF THE PROBLEM AND THAT A POINT DOWN THE RWY HAD BEEN ESTABLISHED FOR ALL TKOF COMPUTATIONS FROM 10L.