B757 CREW DEPARTED LAX WITH THE COMPANY TAILORED FMC ANGEL 2 SID. THE L NAV CALLED FOR A L TURN EARLIER THAN ATC DEEMED APPROPRIATE.

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NOV/XA/99; ANGEL 2 SID RWY 25R LAX ARPT. DEP IS AN FMS ONLY DEP. ACR SPECIAL PAGES HAVE A NOTE ABOUT NOT TURNING BEFORE CROSSING THE SANTA MONICA (SMO) 160 DEG RADIAL. AT 400 FT LNAV WAS SELECTED FOR COURSE GUIDANCE WHICH INDICATED WE HAD DRIFTED L; SMOOG INTERSECTION INDICATED SLIGHTLY R OF PRESENT TRACK. WE CORRECTED R. LAX TWR IMMEDIATELY QUERIED IF WE HAD A 'MAP SHIFT' ON FMS. THEY FURTHER INDICATED THAT THE PREVIOUS NIGHT'S FLT HAD DONE THE SAME THING. ANOTHER FLT HAD CORRECTED L. I WAS REQUESTED TO RPT THE ANOMALY TO MY COMPANY. AFTER MIDNIGHT FLTS ARE USUALLY GIVEN AN FMS DEP. THE ACFT HAD A FULL IRU ALIGNMENT BEFORE PUSHBACK. IF THE B757 ACFT IS NOT CAPABLE OF A REASONABLY SHORT TAXI AND A STRAIGHT OUT DEP; THEN THERE IS A PROB. IF THE POS ARE ALL CORRECT IN THE DATABASE; THE ACFT SIMPLY CANNOT FIND SMOOG CORRECTLY RIGHT AFTER TKOF. IF WE NEED TO TRACK THE CTRLINE PRECISELY; THEN THE PROC; AT LEAST FOR THE ACR B757 SHOULD BE CHANGED TO FLY THE ILS RWY 25R OUTBOUND TO SMOOG; THEN FLY THE FMS TRACK.