Narrative:

We originally had been given the civet 5 runway 25L arrival into lax. We were now given direct tnp and the seavu 1 runway 25L arrival. We were told to descend via the seavu 1; runway 25L. Just passing dixxn about to intercept the runway 25L course we were given descend seavu 1 runway 24R. This is a complicated FMC change; since we have to reinstall the seavu 1 with our original ifp (tnp); put new runway in; and then find the right fix to fly to. I was expecting this since socal is doing this so often now and had finished within 15 seconds of having new course in; but realized that we were almost past the minze point and needed to turn aircraft for runway 24R. The aircraft wouldn't engage in LNAV even though there was no discontinuity and that the next fix was magenta. I had the first officer just heading select the aircraft on the course. We were never off course but LNAV wouldn't engage. We were then cleared for the approach runway 24R but almost immediately that was canceled and told maintain 4000 ft. We were then cleared for approach to runway 24L; with a B747 for runway 24R only 3 and 1/2 mi ahead for the right. Also told to maintain 180 KTS; which became apparent was too fast with the heavy ahead of us. We had to slow down to maintain separation. Socal when giving us runway 24L never gave us a heading; told us to 'just slide it over to the left.' this is the latest I have ever been given a change in the seavu 1 arrival. For this application we were at one time or another given an approach clearance to 3 different runways! We were IMC during most of this maneuver. A very high workload environment for a large aircraft like a B757 to be performing in IMC.

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Original NASA ASRS Text

Title: B757-200 FLT CREW RECEIVES MULTIPLE STAR AND RWY CHANGES DURING LATE STAGES OF ARRIVAL TO LAX.

Narrative: WE ORIGINALLY HAD BEEN GIVEN THE CIVET 5 RWY 25L ARR INTO LAX. WE WERE NOW GIVEN DIRECT TNP AND THE SEAVU 1 RWY 25L ARR. WE WERE TOLD TO DSND VIA THE SEAVU 1; RWY 25L. JUST PASSING DIXXN ABOUT TO INTERCEPT THE RWY 25L COURSE WE WERE GIVEN DSND SEAVU 1 RWY 24R. THIS IS A COMPLICATED FMC CHANGE; SINCE WE HAVE TO REINSTALL THE SEAVU 1 WITH OUR ORIGINAL IFP (TNP); PUT NEW RWY IN; AND THEN FIND THE RIGHT FIX TO FLY TO. I WAS EXPECTING THIS SINCE SOCAL IS DOING THIS SO OFTEN NOW AND HAD FINISHED WITHIN 15 SECONDS OF HAVING NEW COURSE IN; BUT REALIZED THAT WE WERE ALMOST PAST THE MINZE POINT AND NEEDED TO TURN ACFT FOR RWY 24R. THE ACFT WOULDN'T ENGAGE IN LNAV EVEN THOUGH THERE WAS NO DISCONTINUITY AND THAT THE NEXT FIX WAS MAGENTA. I HAD THE FO JUST HDG SELECT THE ACFT ON THE COURSE. WE WERE NEVER OFF COURSE BUT LNAV WOULDN'T ENGAGE. WE WERE THEN CLRED FOR THE APCH RWY 24R BUT ALMOST IMMEDIATELY THAT WAS CANCELED AND TOLD MAINTAIN 4000 FT. WE WERE THEN CLRED FOR APCH TO RWY 24L; WITH A B747 FOR RWY 24R ONLY 3 AND 1/2 MI AHEAD FOR THE R. ALSO TOLD TO MAINTAIN 180 KTS; WHICH BECAME APPARENT WAS TOO FAST WITH THE HVY AHEAD OF US. WE HAD TO SLOW DOWN TO MAINTAIN SEPARATION. SOCAL WHEN GIVING US RWY 24L NEVER GAVE US A HDG; TOLD US TO 'JUST SLIDE IT OVER TO THE L.' THIS IS THE LATEST I HAVE EVER BEEN GIVEN A CHANGE IN THE SEAVU 1 ARR. FOR THIS APPLICATION WE WERE AT ONE TIME OR ANOTHER GIVEN AN APCH CLRNC TO 3 DIFFERENT RWYS! WE WERE IMC DURING MOST OF THIS MANEUVER. A VERY HIGH WORKLOAD ENVIRONMENT FOR A LARGE ACFT LIKE A B757 TO BE PERFORMING IN IMC.

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.