A B757 CREW; DEPARTING LAX; EXPERIENCED AN UNWANTED 5 DEG L TURN; WHEN THE LNAV WAS SELECTED.

Narrative

FLT WAS FILED AND CLRED ON THE 'ANGEL 2 FMS DEP' FROM LAX; DAGGETT TRANSITION. THE FMS WAS ALIGNED TO THE ARPT REF POINT (N3356.6 W11824.5). GND SPD AVERAGE AFTER ALIGNMENT WAS NOTED AT 1 KT AND A MAP COMPARISON WAS MADE AT THE END OF RWY 25R; POS WAS SLIGHTLY N OF RWY DEPICTION AND NOT CONSIDERED SIGNIFICANT. AFTER 400 FT AGL; LNAV WAS SELECTED; THE BANK STEERING BAR COMMANDED A SLIGHT (5 DEG) L TURN TOWARDS THE FIRST POINT 'SMOOG' RATHER THAN COMMANDING THE 249 DEG RADIAL REQUIRED. THE COPLT FLYING NOTICED THE CHANGE AND WE CAME BACK RIGHT TO THE REQUIRED HDG. ARPT NOISE PROCS DICTATE NO TURNS AFTER TKOF UNTIL THE SMO VOR 160 DEG RADIAL. EVEN THOUGH WE HAD COMPLIED WITH COMPANY ALIGNMENT AND TAXI PROCS THE SLIGHT MAP DEV ON DEP AND THE PROX OF THE FIRST RNAV FIX RESULTED IN A COMMANDED TURN THAT COULD CONFLICT WITH REQUIRED NOISE ABATEMENT PROCS. COMMENTS: 1) ARPT REF POINTS AND QUICK 30 SECOND ALIGNMENTS DO NOT ASSURE ACCURACY DURING THE INITIAL PHASE OF RNAV DEPS. 2) 10 NM SCALE MAP DISPLAYS ARE NOT ACCURATE ENOUGH TO ACCESS MAP/FMS DEV. 3) THERE ARE NO ENG OR RWY COORDINATES AVAILABLE EXCEPT BY THE LATITUDE/LONGITUDE SCALE ON THE ARPT PAGE; EASY TO MAKE MISTAKES. 4) THERE ARE NO RAW DATA REFS ON RNAV DEPS AND AIRWAYS TO CHK FOR MAP DRIFT; OR BACK-UP IN CASE OF MAP FAILURE.