Narrative:

Our clearance was the lax 5 (250 degree heading to smo 160 degree radial then left turn to 220 degrees). We were to keep the saab aircraft ahead in sight as he will be turning sbound. After takeoff while completing PNF duties; I realize we are turning prior to the smo 160 degree radial. Simultaneously; the lax tower must have recognized the early turn and advised us to fly the lax 5 as published. We immediately stopped our turn and continued straight out. We were handed off to socal departure and asked if the tower had given us an early turn. I replied they had not; but while my attention was diverted I had lost sight of the saab. Socal told us to stop our climb; which we did. Once clear; we continued our climb and were handed off to the next sector. In discussing the events with the first officer; he told me he had never lost sight of the saab. It's hard to say what caused this situation. We were originally anticipating runway 24L and had that set in the FMC; as we taxied to runway 25R I changed the runway in the computer and made sure the 160 degree radial was in the legs page; however; we did not verbally discuss the procedure and turn; and this may have contributed to the error. Because the departure procedure is different depending on runways we should have briefed the prohibition to the turn prior to the smo 160 degree radial. Supplemental information from acn 703299: in 10 yrs of flying out of lax; I have departed on sbound flts from the 25 runways roughly 25-30 times. And in each case; immediately after takeoff; contrary to the published departure procedure directing a turn at the smo 160 degree radial and the taxiway signage prohibiting any turns prior to the shoreline; had been given the clearance; 'start your turn now; and contact departure.' it's also very common; when operating a sbound departure from the 24 runways; to be issued a turn to 210 degrees or 220 degrees. And; similarly; immediately after takeoff; and well before reaching the shoreline; it's very routine to be told to 'start your turn now.' this was a case of someone hearing what they 'expected' to hear; and doing what they 'anticipated' they would be cleared to do. I had briefed the departure with references to the laxx 2 chart regarding the turn to 220 degrees at the smo 160 degree radial; and the taxiway signs stating 'no turns before the shoreline.' I also briefed that I expected to be cleared to start the turn well before the radial. I had the 160 degree radial depicted on my map; but started the turn early anticipating the clearance I had always received in the past.

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Original NASA ASRS Text

Title: B737-900 FLT CREW HAS A HDG TRACK DEV DURING THE LAX 5 DEP.

Narrative: OUR CLRNC WAS THE LAX 5 (250 DEG HDG TO SMO 160 DEG RADIAL THEN L TURN TO 220 DEGS). WE WERE TO KEEP THE SAAB ACFT AHEAD IN SIGHT AS HE WILL BE TURNING SBOUND. AFTER TKOF WHILE COMPLETING PNF DUTIES; I REALIZE WE ARE TURNING PRIOR TO THE SMO 160 DEG RADIAL. SIMULTANEOUSLY; THE LAX TWR MUST HAVE RECOGNIZED THE EARLY TURN AND ADVISED US TO FLY THE LAX 5 AS PUBLISHED. WE IMMEDIATELY STOPPED OUR TURN AND CONTINUED STRAIGHT OUT. WE WERE HANDED OFF TO SOCAL DEP AND ASKED IF THE TWR HAD GIVEN US AN EARLY TURN. I REPLIED THEY HAD NOT; BUT WHILE MY ATTN WAS DIVERTED I HAD LOST SIGHT OF THE SAAB. SOCAL TOLD US TO STOP OUR CLB; WHICH WE DID. ONCE CLR; WE CONTINUED OUR CLB AND WERE HANDED OFF TO THE NEXT SECTOR. IN DISCUSSING THE EVENTS WITH THE FO; HE TOLD ME HE HAD NEVER LOST SIGHT OF THE SAAB. IT'S HARD TO SAY WHAT CAUSED THIS SITUATION. WE WERE ORIGINALLY ANTICIPATING RWY 24L AND HAD THAT SET IN THE FMC; AS WE TAXIED TO RWY 25R I CHANGED THE RWY IN THE COMPUTER AND MADE SURE THE 160 DEG RADIAL WAS IN THE LEGS PAGE; HOWEVER; WE DID NOT VERBALLY DISCUSS THE PROC AND TURN; AND THIS MAY HAVE CONTRIBUTED TO THE ERROR. BECAUSE THE DEP PROC IS DIFFERENT DEPENDING ON RWYS WE SHOULD HAVE BRIEFED THE PROHIBITION TO THE TURN PRIOR TO THE SMO 160 DEG RADIAL. SUPPLEMENTAL INFO FROM ACN 703299: IN 10 YRS OF FLYING OUT OF LAX; I HAVE DEPARTED ON SBOUND FLTS FROM THE 25 RWYS ROUGHLY 25-30 TIMES. AND IN EACH CASE; IMMEDIATELY AFTER TKOF; CONTRARY TO THE PUBLISHED DEP PROC DIRECTING A TURN AT THE SMO 160 DEG RADIAL AND THE TXWY SIGNAGE PROHIBITING ANY TURNS PRIOR TO THE SHORELINE; HAD BEEN GIVEN THE CLRNC; 'START YOUR TURN NOW; AND CONTACT DEP.' IT'S ALSO VERY COMMON; WHEN OPERATING A SBOUND DEP FROM THE 24 RWYS; TO BE ISSUED A TURN TO 210 DEGS OR 220 DEGS. AND; SIMILARLY; IMMEDIATELY AFTER TKOF; AND WELL BEFORE REACHING THE SHORELINE; IT'S VERY ROUTINE TO BE TOLD TO 'START YOUR TURN NOW.' THIS WAS A CASE OF SOMEONE HEARING WHAT THEY 'EXPECTED' TO HEAR; AND DOING WHAT THEY 'ANTICIPATED' THEY WOULD BE CLRED TO DO. I HAD BRIEFED THE DEP WITH REFS TO THE LAXX 2 CHART REGARDING THE TURN TO 220 DEGS AT THE SMO 160 DEG RADIAL; AND THE TXWY SIGNS STATING 'NO TURNS BEFORE THE SHORELINE.' I ALSO BRIEFED THAT I EXPECTED TO BE CLRED TO START THE TURN WELL BEFORE THE RADIAL. I HAD THE 160 DEG RADIAL DEPICTED ON MY MAP; BUT STARTED THE TURN EARLY ANTICIPATING THE CLRNC I HAD ALWAYS RECEIVED IN THE PAST.

Data retrieved from NASA's ASRS site as of January 2009 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.