Narrative:

Descent into lax on seavu one arrival. Arrival plate notes indicate aircraft should proceed via runway 25L unless otherwise instructed by ATC; but that runway is notamed closed for construction. We set up for the north complex runway 24R as the majority of our flights are sent to the north side to expedite our aircraft flow. We were cleared to descend via the arrival and on descent between konzl and cataw intersections; we were told to expect runway 25R as the north complex would be unavailable. The captain/pilot monitoring went heads down to change the FMC while I continued to fly the arrival and track the altitude restrictions. LNAV and ap engaged. Approaching cataw intersection at 14000 ft I reviewed the arrival for the next altitude; placed it in the altitude window and double checked the next fix and altitude. Moments after passing cataw I noticed the aircraft didn't turn north as per the arrival. I double checked the plate; verbally announced that the autopilot missed the turn and turned the heading indicator to a heading that would put us back on course. During this time we flew approximately 1/2 mile off the arrival. While in the turn; socal called and announced that we didn't turn to seavu. Another controller took over and issued a heading; altitude; clearance to join the localizer and gave the localizer frequency. From this I understood that the controller was aware that the change of runways had us scrambling to make navigation changes close in on the arrival and after the descent via the arrival clearance was issued. We continued to the localizer and landed uneventfully on runway 25R. In later discussion with the captain; it became apparent that while making the FMC changes; the route likely dropped due to a discontinuity; the LNAV disengaged and the aircraft continued straight ahead on heading after cataw. I didn't catch the LNAV change while double checking the next fix on the plate and altitude setting in the window and the captain missed it while changing the runway and arrival fix sequence. I had lax VOR active on my radio for DME rather than the crossing radial to pomona VOR that would have also clued me in that the autopilot wasn't piloting very well; and neither was I. This is a high workload arrival (as are others into lax) with some 14 step-down fixes prior to the approach. Runway changes close in make for conditions that can tax the coordination of the best of crews. While I understand that runway changes may be necessary at times due to traffic; I feel that close-in on the arrival; a runway change should be followed with ATC vectors rather than lose one pilot to FMC changes while the other deals with an even higher workload flying and monitoring alone. We should have been better prepared for the possible change and briefed how we would respond. The note on the arrival should be changed while runway 25L is closed for construction. We were expecting the north complex as is the usual routine; but were left scrambling and unprepared.

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Original NASA ASRS Text

Title: B737-700 FLT CREW HAS TRACK/HEADING DEVIATION DURING SEAVU ONE ARR TO LAX.

Narrative: DESCENT INTO LAX ON SEAVU ONE ARRIVAL. ARRIVAL PLATE NOTES INDICATE ACFT SHOULD PROCEED VIA RWY 25L UNLESS OTHERWISE INSTRUCTED BY ATC; BUT THAT RWY IS NOTAMED CLOSED FOR CONSTRUCTION. WE SET UP FOR THE NORTH COMPLEX RWY 24R AS THE MAJORITY OF OUR FLIGHTS ARE SENT TO THE NORTH SIDE TO EXPEDITE OUR AIRCRAFT FLOW. WE WERE CLEARED TO DESCEND VIA THE ARRIVAL AND ON DESCENT BETWEEN KONZL AND CATAW INTERSECTIONS; WE WERE TOLD TO EXPECT RWY 25R AS THE NORTH COMPLEX WOULD BE UNAVAILABLE. THE CAPTAIN/PILOT MONITORING WENT HEADS DOWN TO CHANGE THE FMC WHILE I CONTINUED TO FLY THE ARRIVAL AND TRACK THE ALTITUDE RESTRICTIONS. LNAV AND AP ENGAGED. APPROACHING CATAW INTERSECTION AT 14000 FT I REVIEWED THE ARRIVAL FOR THE NEXT ALTITUDE; PLACED IT IN THE ALTITUDE WINDOW AND DOUBLE CHECKED THE NEXT FIX AND ALTITUDE. MOMENTS AFTER PASSING CATAW I NOTICED THE AIRCRAFT DIDN'T TURN NORTH AS PER THE ARRIVAL. I DOUBLE CHECKED THE PLATE; VERBALLY ANNOUNCED THAT THE AUTOPILOT MISSED THE TURN AND TURNED THE HEADING INDICATOR TO A HEADING THAT WOULD PUT US BACK ON COURSE. DURING THIS TIME WE FLEW APPROXIMATELY 1/2 MILE OFF THE ARRIVAL. WHILE IN THE TURN; SOCAL CALLED AND ANNOUNCED THAT WE DIDN'T TURN TO SEAVU. ANOTHER CONTROLLER TOOK OVER AND ISSUED A HEADING; ALTITUDE; CLEARANCE TO JOIN THE LOCALIZER AND GAVE THE LOC FREQUENCY. FROM THIS I UNDERSTOOD THAT THE CONTROLLER WAS AWARE THAT THE CHANGE OF RWYS HAD US SCRAMBLING TO MAKE NAVIGATION CHANGES CLOSE IN ON THE ARRIVAL AND AFTER THE DESCENT VIA THE ARRIVAL CLEARANCE WAS ISSUED. WE CONTINUED TO THE LOCALIZER AND LANDED UNEVENTFULLY ON RWY 25R. IN LATER DISCUSSION WITH THE CAPTAIN; IT BECAME APPARENT THAT WHILE MAKING THE FMC CHANGES; THE ROUTE LIKELY DROPPED DUE TO A DISCONTINUITY; THE LNAV DISENGAGED AND THE AIRCRAFT CONTINUED STRAIGHT AHEAD ON HEADING AFTER CATAW. I DIDN'T CATCH THE LNAV CHANGE WHILE DOUBLE CHECKING THE NEXT FIX ON THE PLATE AND ALTITUDE SETTING IN THE WINDOW AND THE CAPTAIN MISSED IT WHILE CHANGING THE RUNWAY AND ARRIVAL FIX SEQUENCE. I HAD LAX VOR ACTIVE ON MY RADIO FOR DME RATHER THAN THE CROSSING RADIAL TO POMONA VOR THAT WOULD HAVE ALSO CLUED ME IN THAT THE AUTOPILOT WASN'T PILOTING VERY WELL; AND NEITHER WAS I. THIS IS A HIGH WORKLOAD ARRIVAL (AS ARE OTHERS INTO LAX) WITH SOME 14 STEP-DOWN FIXES PRIOR TO THE APPROACH. RUNWAY CHANGES CLOSE IN MAKE FOR CONDITIONS THAT CAN TAX THE COORDINATION OF THE BEST OF CREWS. WHILE I UNDERSTAND THAT RUNWAY CHANGES MAY BE NECESSARY AT TIMES DUE TO TRAFFIC; I FEEL THAT CLOSE-IN ON THE ARRIVAL; A RUNWAY CHANGE SHOULD BE FOLLOWED WITH ATC VECTORS RATHER THAN LOSE ONE PILOT TO FMC CHANGES WHILE THE OTHER DEALS WITH AN EVEN HIGHER WORKLOAD FLYING AND MONITORING ALONE. WE SHOULD HAVE BEEN BETTER PREPARED FOR THE POSSIBLE CHANGE AND BRIEFED HOW WE WOULD RESPOND. THE NOTE ON THE ARRIVAL SHOULD BE CHANGED WHILE RWY 25L IS CLOSED FOR CONSTRUCTION. WE WERE EXPECTING THE NORTH COMPLEX AS IS THE USUAL ROUTINE; BUT WERE LEFT SCRAMBLING AND UNPREPARED.

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.