Narrative:

It was the fourth leg of a long day crossing the country from east coast to west; marked with much en route WX (thunderstorms) and a couple of instrument apches. I was the PF and we were descending for the seavu one arrival into lax. Before we reached FL180; we had to brief an ILS into lax; as the WX was reported as overcast at 700 ft. As we were still talking to lax center; we did not have knowledge of which runway to expect; so we briefed the most likely approach; the ILS runway 24R. We did not get handed to socal approach until over konzl intersection. Socal then advised us to expect the ILS runway 25L; GS inoperative. Since I was busy with flying the step down fixes on the seavu arrival; my captain began setting up the new approach in the FMC; set the navigation radios to the new frequency; and read aloud the new minimums and tdze. So he basically briefed the highlights of the approach; while I glanced at the chart in between making the step down restrs. After crossing limma (FAF); I commenced a descent to the localizer (GS out) MDA of 600 ft. We broke out right at 700 ft; and saw the airport immediately. I rolled the vsi to smoothly level at 600 ft. Just after level off; lax tower advised us to check our altimeter setting; as they were getting a low altitude warning on us. The altimeters were set correctly; and it was then that I realized I had descended to 600 ft too early; as our DME was passing through 4.5 from the localizer; which was still one mile east of ladle. The captain then advised the tower we had the airport in sight and were proceeding visually. By the time we started correcting the altitude; we were within 3.5 DME; and we descended visually to the runway. This incident really made me think a lot about preventing similar instances in the future. This is definitely a mistake I will not make again. First off; when we received the assignment for the ILS runway 25R; I failed to give the control of the aircraft to the captain; so that I could brief the approach and be better familiar with the step down fixes. Once we received the runway 25L assignment; the captain quickly tried to make all the necessary changes and read aloud the highlights; but in retrospect; I should have briefed the approach that I would fly to completion. I was far too lax about briefing the approach; and especially being aware of the minimums peculiar to the localizer only approach. Second; the captain; as pm; missed my mistake in not leveling off prior to reaching ladle. I'd like to mention several contributing factors which helped contribute to this incident. First; is the fact the lax typically does not assign a runway until the crew is in the throes of a very busy arrival. It is unfortunate that there cannot be an earlier awareness of which approach will be flown; so that a briefing can be comfortably completed before becoming completely consumed with a new altitude every 3-7 miles; speed restrs; and traffic advisories. Second; and very key; was the fact that the ladle step down fix did not appear in the FMC with the ILS runway 25L approach programmed. Perhaps this is because the fix is superfluous when flying the full ILS; but it is a good reminder to check that all fixes are in the FMC; or at the very least to be aware that some may not appear. It would be easy to assume that the crew had passed the fix; just because the next fix on the legs page is the runway (or map). Finally; in my humble opinion; it seems that our procedures should allow for the setting of step down altitudes after the FAF. If our pilots are pre-programmed only to set the MDA; I believe it will lead to a better chance of missing these step down fixes. When time is of the essence and crews are swamped with tasks; it is possible to inadvertently begin paying attention only to items that are absolutely necessary for the logistics of setting up the approach. The result is paying much more attention to the MDA which needs setting; to the neglect of the other altitude that is smaller and buried within the profile view of the approach chart. I humbly but strongly submit that our procedures allow us to set these altitudes; before a crew misses one and has a close encounter with terrain or obstructions. Again; though; it is clear to me that the ultimate correction is to fully and completely look at all aspects of the approach; especially those which occur as one descends closer to terrain. I will not miss this again.

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Original NASA ASRS Text

Title: A B737 ON THE LAX SEAVU ARR WAS GIVEN A LATE RWY ASSIGNMENT TO RWY 25L WITH THE GS OTS. CREW DSNDED BELOW MDA PRIOR TO FAF THEN RECEIVED LOW ALT WARNING.

Narrative: IT WAS THE FOURTH LEG OF A LONG DAY CROSSING THE COUNTRY FROM EAST COAST TO WEST; MARKED WITH MUCH ENRTE WX (THUNDERSTORMS) AND A COUPLE OF INSTRUMENT APCHES. I WAS THE PF AND WE WERE DSNDING FOR THE SEAVU ONE ARR INTO LAX. BEFORE WE REACHED FL180; WE HAD TO BRIEF AN ILS INTO LAX; AS THE WX WAS RPTED AS OVERCAST AT 700 FT. AS WE WERE STILL TALKING TO LAX CENTER; WE DID NOT HAVE KNOWLEDGE OF WHICH RWY TO EXPECT; SO WE BRIEFED THE MOST LIKELY APCH; THE ILS RWY 24R. WE DID NOT GET HANDED TO SOCAL APCH UNTIL OVER KONZL INTXN. SOCAL THEN ADVISED US TO EXPECT THE ILS RWY 25L; GS INOPERATIVE. SINCE I WAS BUSY WITH FLYING THE STEP DOWN FIXES ON THE SEAVU ARR; MY CAPT BEGAN SETTING UP THE NEW APCH IN THE FMC; SET THE NAV RADIOS TO THE NEW FREQUENCY; AND READ ALOUD THE NEW MINIMUMS AND TDZE. SO HE BASICALLY BRIEFED THE HIGHLIGHTS OF THE APCH; WHILE I GLANCED AT THE CHART IN BETWEEN MAKING THE STEP DOWN RESTRS. AFTER CROSSING LIMMA (FAF); I COMMENCED A DSCNT TO THE LOC (GS OUT) MDA OF 600 FT. WE BROKE OUT RIGHT AT 700 FT; AND SAW THE ARPT IMMEDIATELY. I ROLLED THE VSI TO SMOOTHLY LEVEL AT 600 FT. JUST AFTER LEVEL OFF; LAX TOWER ADVISED US TO CHECK OUR ALTIMETER SETTING; AS THEY WERE GETTING A LOW ALTITUDE WARNING ON US. THE ALTIMETERS WERE SET CORRECTLY; AND IT WAS THEN THAT I REALIZED I HAD DSNDED TO 600 FT TOO EARLY; AS OUR DME WAS PASSING THROUGH 4.5 FROM THE LOC; WHICH WAS STILL ONE MILE EAST OF LADLE. THE CAPT THEN ADVISED THE TOWER WE HAD THE ARPT IN SIGHT AND WERE PROCEEDING VISUALLY. BY THE TIME WE STARTED CORRECTING THE ALTITUDE; WE WERE WITHIN 3.5 DME; AND WE DSNDED VISUALLY TO THE RWY. THIS INCIDENT REALLY MADE ME THINK A LOT ABOUT PREVENTING SIMILAR INSTANCES IN THE FUTURE. THIS IS DEFINITELY A MISTAKE I WILL NOT MAKE AGAIN. FIRST OFF; WHEN WE RECEIVED THE ASSIGNMENT FOR THE ILS RWY 25R; I FAILED TO GIVE THE CONTROL OF THE ACFT TO THE CAPT; SO THAT I COULD BRIEF THE APCH AND BE BETTER FAMILIAR WITH THE STEP DOWN FIXES. ONCE WE RECEIVED THE RWY 25L ASSIGNMENT; THE CAPT QUICKLY TRIED TO MAKE ALL THE NECESSARY CHANGES AND READ ALOUD THE HIGHLIGHTS; BUT IN RETROSPECT; I SHOULD HAVE BRIEFED THE APCH THAT I WOULD FLY TO COMPLETION. I WAS FAR TOO LAX ABOUT BRIEFING THE APCH; AND ESPECIALLY BEING AWARE OF THE MINIMUMS PECULIAR TO THE LOC ONLY APCH. SECOND; THE CAPT; AS PM; MISSED MY MISTAKE IN NOT LEVELING OFF PRIOR TO REACHING LADLE. I'D LIKE TO MENTION SEVERAL CONTRIBUTING FACTORS WHICH HELPED CONTRIBUTE TO THIS INCIDENT. FIRST; IS THE FACT THE LAX TYPICALLY DOES NOT ASSIGN A RWY UNTIL THE CREW IS IN THE THROES OF A VERY BUSY ARR. IT IS UNFORTUNATE THAT THERE CANNOT BE AN EARLIER AWARENESS OF WHICH APCH WILL BE FLOWN; SO THAT A BRIEFING CAN BE COMFORTABLY COMPLETED BEFORE BECOMING COMPLETELY CONSUMED WITH A NEW ALTITUDE EVERY 3-7 MILES; SPEED RESTRS; AND TFC ADVISORIES. SECOND; AND VERY KEY; WAS THE FACT THAT THE LADLE STEP DOWN FIX DID NOT APPEAR IN THE FMC WITH THE ILS RWY 25L APCH PROGRAMMED. PERHAPS THIS IS BECAUSE THE FIX IS SUPERFLUOUS WHEN FLYING THE FULL ILS; BUT IT IS A GOOD REMINDER TO CHECK THAT ALL FIXES ARE IN THE FMC; OR AT THE VERY LEAST TO BE AWARE THAT SOME MAY NOT APPEAR. IT WOULD BE EASY TO ASSUME THAT THE CREW HAD PASSED THE FIX; JUST BECAUSE THE NEXT FIX ON THE LEGS PAGE IS THE RWY (OR MAP). FINALLY; IN MY HUMBLE OPINION; IT SEEMS THAT OUR PROCS SHOULD ALLOW FOR THE SETTING OF STEP DOWN ALTITUDES AFTER THE FAF. IF OUR PLTS ARE PRE-PROGRAMMED ONLY TO SET THE MDA; I BELIEVE IT WILL LEAD TO A BETTER CHANCE OF MISSING THESE STEP DOWN FIXES. WHEN TIME IS OF THE ESSENCE AND CREWS ARE SWAMPED WITH TASKS; IT IS POSSIBLE TO INADVERTENTLY BEGIN PAYING ATTENTION ONLY TO ITEMS THAT ARE ABSOLUTELY NECESSARY FOR THE LOGISTICS OF SETTING UP THE APCH. THE RESULT IS PAYING MUCH MORE ATTENTION TO THE MDA WHICH NEEDS SETTING; TO THE NEGLECT OF THE OTHER ALTITUDE THAT IS SMALLER AND BURIED WITHIN THE PROFILE VIEW OF THE APCH CHART. I HUMBLY BUT STRONGLY SUBMIT THAT OUR PROCS ALLOW US TO SET THESE ALTITUDES; BEFORE A CREW MISSES ONE AND HAS A CLOSE ENCOUNTER WITH TERRAIN OR OBSTRUCTIONS. AGAIN; THOUGH; IT IS CLEAR TO ME THAT THE ULTIMATE CORRECTION IS TO FULLY AND COMPLETELY LOOK AT ALL ASPECTS OF THE APCH; ESPECIALLY THOSE WHICH OCCUR AS ONE DSNDS CLOSER TO TERRAIN. I WILL NOT MISS THIS AGAIN.

Data retrieved from NASA's ASRS site as of May 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.