Narrative:

Nov/xa/99, angel 2 SID runway 25R lax airport. Departure is an FMS only departure. Air carrier special pages have a note about not turning before crossing the santa monica (smo) 160 degree radial. At 400 ft LNAV was selected for course guidance which indicated we had drifted left, smoog intersection indicated slightly right of present track. We corrected right. Lax tower immediately queried if we had a 'map shift' on FMS. They further indicated that the previous night's flight had done the same thing. Another flight had corrected left. I was requested to report the anomaly to my company. After midnight flts are usually given an FMS departure. The aircraft had a full IRU alignment before pushback. If the B757 aircraft is not capable of a reasonably short taxi and a straight out departure, then there is a problem. If the position are all correct in the database, the aircraft simply cannot find smoog correctly right after takeoff. If we need to track the centerline precisely, then the procedure, at least for the air carrier B757 should be changed to fly the ILS runway 25R outbound to smoog, then fly the FMS track.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.