Narrative:

Intercepted ILS localizer course to runway 25L at lax from pdz 3 arrival. Captain flying, and he was flying using map mode on HSI. I was monitoring raw data ILS on my HSI and began noticing a DME related problem. From ILS DME, I was showing that we were passing fixes, while captain was still showing the fix out in front of us on his HSI map. I pointed this out and we began to get high on the approach profile. At the same time, I began to notice we were drifting left of course and mentioned this to the captain. He noted that we were on course according to his HSI map display. We continued drifting left and I told the captain that I was showing full scale deflection. He turned back aggressively to correct to course and we rejoined localizer course. I would guess that we ended up approximately 2 mi or so left of localizer course when we corrected back. We were visual with the airport from about 10 mi out but since the wind showed to be about 35 KTS out of the south on the HSI, I thought that it was probably taking a lot of left crab to maintain course. This contributed to my confusion as to the degree to which we were drifting left. The captain and I had read the F-4 regarding the map shift at lax, so we realized what was happening. It just took a little time to put it all together. I would recommend all crews fly raw data until the FMS problem is fixed. Supplemental information from acn 445009: while on the pdz 3 arrival into lax, we experienced a map shift. While tracking the FMC, my first officer monitored raw data and observed errors on the approach. Inside gate, we received a series of successive airspeed changes from ATC, and with the errors in DME to identify our crossing fixes, my distraction allowed us to be south of the centerline of runway 25L. We were approximately 1-2 mi south of centerline before correcting back. This is an estimate, as we had no way of accurately determining this distance. We were also a bit high on approach as our xings were a confusion from displayed information and raw data. By the time I noticed the differences between the FMC map display and raw data, we were off our intended track. ATC did not make any reference to this, nor seemed upset with our deviation. We landed on the touchdown zone at the proper point and at proper speed. The distrs between what was displayed on the FMC and raw data, and the quick adjustments from ATC seemed to all come together at the most inopportune moment. Callback conversation with reporter acn 445010 revealed the following information: the captain was unable to provide any additional detail. The first officer was not in town.

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Original NASA ASRS Text

Title: B757 CREW EXPERIENCED MAP SHIFT ON ARR AT LAX.

Narrative: INTERCEPTED ILS LOC COURSE TO RWY 25L AT LAX FROM PDZ 3 ARR. CAPT FLYING, AND HE WAS FLYING USING MAP MODE ON HSI. I WAS MONITORING RAW DATA ILS ON MY HSI AND BEGAN NOTICING A DME RELATED PROB. FROM ILS DME, I WAS SHOWING THAT WE WERE PASSING FIXES, WHILE CAPT WAS STILL SHOWING THE FIX OUT IN FRONT OF US ON HIS HSI MAP. I POINTED THIS OUT AND WE BEGAN TO GET HIGH ON THE APCH PROFILE. AT THE SAME TIME, I BEGAN TO NOTICE WE WERE DRIFTING L OF COURSE AND MENTIONED THIS TO THE CAPT. HE NOTED THAT WE WERE ON COURSE ACCORDING TO HIS HSI MAP DISPLAY. WE CONTINUED DRIFTING L AND I TOLD THE CAPT THAT I WAS SHOWING FULL SCALE DEFLECTION. HE TURNED BACK AGGRESSIVELY TO CORRECT TO COURSE AND WE REJOINED LOC COURSE. I WOULD GUESS THAT WE ENDED UP APPROX 2 MI OR SO L OF LOC COURSE WHEN WE CORRECTED BACK. WE WERE VISUAL WITH THE ARPT FROM ABOUT 10 MI OUT BUT SINCE THE WIND SHOWED TO BE ABOUT 35 KTS OUT OF THE S ON THE HSI, I THOUGHT THAT IT WAS PROBABLY TAKING A LOT OF L CRAB TO MAINTAIN COURSE. THIS CONTRIBUTED TO MY CONFUSION AS TO THE DEG TO WHICH WE WERE DRIFTING L. THE CAPT AND I HAD READ THE F-4 REGARDING THE MAP SHIFT AT LAX, SO WE REALIZED WHAT WAS HAPPENING. IT JUST TOOK A LITTLE TIME TO PUT IT ALL TOGETHER. I WOULD RECOMMEND ALL CREWS FLY RAW DATA UNTIL THE FMS PROB IS FIXED. SUPPLEMENTAL INFO FROM ACN 445009: WHILE ON THE PDZ 3 ARR INTO LAX, WE EXPERIENCED A MAP SHIFT. WHILE TRACKING THE FMC, MY FO MONITORED RAW DATA AND OBSERVED ERRORS ON THE APCH. INSIDE GATE, WE RECEIVED A SERIES OF SUCCESSIVE AIRSPD CHANGES FROM ATC, AND WITH THE ERRORS IN DME TO IDENT OUR XING FIXES, MY DISTR ALLOWED US TO BE S OF THE CTRLINE OF RWY 25L. WE WERE APPROX 1-2 MI S OF CTRLINE BEFORE CORRECTING BACK. THIS IS AN ESTIMATE, AS WE HAD NO WAY OF ACCURATELY DETERMINING THIS DISTANCE. WE WERE ALSO A BIT HIGH ON APCH AS OUR XINGS WERE A CONFUSION FROM DISPLAYED INFO AND RAW DATA. BY THE TIME I NOTICED THE DIFFERENCES BTWN THE FMC MAP DISPLAY AND RAW DATA, WE WERE OFF OUR INTENDED TRACK. ATC DID NOT MAKE ANY REF TO THIS, NOR SEEMED UPSET WITH OUR DEV. WE LANDED ON THE TOUCHDOWN ZONE AT THE PROPER POINT AND AT PROPER SPD. THE DISTRS BTWN WHAT WAS DISPLAYED ON THE FMC AND RAW DATA, AND THE QUICK ADJUSTMENTS FROM ATC SEEMED TO ALL COME TOGETHER AT THE MOST INOPPORTUNE MOMENT. CALLBACK CONVERSATION WITH RPTR ACN 445010 REVEALED THE FOLLOWING INFO: THE CAPT WAS UNABLE TO PROVIDE ANY ADDITIONAL DETAIL. THE FO WAS NOT IN TOWN.

Data retrieved from NASA's ASRS site as of July 2007 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.