Narrative:

It was a beautiful morning in scel. I had reviewed the andes 4 arrival and the CAT IIIA ILS runway 17 as well as the commercial chart in prep for the approach and ldg. We started the briefing before T/D, but completed it during the descent. We knew the potential for map shift existed, but did not mention it in the brief. We were all very aware of the high terrain descending in clear skies into scel. I had tuned the tbn 355 radial, but did not refer to it during the descent, using instead LNAV on the map mode. Dscnding through approximately FL150 the first officer checked the VOR course and found us to be left of course approximately 5 NM. At the same time scel approach wanted to know why almost every 767 was off course. I confirmed the deviation and corrected back on, subsequently disregarding the map and completing the rest of the arrival and CAT III autoland with no further problems using raw data. Causing factors: briefing should be completed prior to descent. Recommend PF to be on raw data during the descent using the map as a backup especially in IMC conditions. Callback conversation with reporter revealed the following information: reporter stated that the information related to the possibility of a map shift is on a company chart. The page does not stated where it occurs. Reporter is of the opinion that it occurs because of the high surrounding terrain. Once the aircraft approachs and passes tbn VORTAC the IRU updates the map position. The terrain to the east when 40 miles out is anywhere from 15,000 ft to 20,000 ft high. The approach controllers are very good at monitoring the acfts progress. The 767's were off course more that day than usual. On the ground the reporter talked with crews of other us carriers and they all noted the map shift. He doesn't know if their company policy requires monitoring of the raw data as his company does. He feels that a note on the arrival page, as well as the present note on airport chart is warranted regarding the need to monitor and navigate by the raw data because of map shifts north of tbn.

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Original NASA ASRS Text

Title: MAP SHIFT PROB. A B-767-300 FLC NOTES THEY ARE LEFT OF THE 355 DEG RADIAL OF TBN VORTAC WHILE USING THEIR FMS MAP DISPLAY FOR GUIDANCE. SCEL APCH CTLR ISSUES ALERT THAT ALL B-767'S HAVE BEEN OFF COURSE N OF TBN VOR ON ANDES 4 ARR TO SCEL, FO.

Narrative: IT WAS A BEAUTIFUL MORNING IN SCEL. I HAD REVIEWED THE ANDES 4 ARR AND THE CAT IIIA ILS RWY 17 AS WELL AS THE COMMERCIAL CHART IN PREP FOR THE APCH AND LDG. WE STARTED THE BRIEFING BEFORE T/D, BUT COMPLETED IT DURING THE DSCNT. WE KNEW THE POTENTIAL FOR MAP SHIFT EXISTED, BUT DID NOT MENTION IT IN THE BRIEF. WE WERE ALL VERY AWARE OF THE HIGH TERRAIN DESCENDING IN CLEAR SKIES INTO SCEL. I HAD TUNED THE TBN 355 RADIAL, BUT DID NOT REFER TO IT DURING THE DSCNT, USING INSTEAD LNAV ON THE MAP MODE. DSCNDING THROUGH APPROX FL150 THE FO CHKED THE VOR COURSE AND FOUND US TO BE LEFT OF COURSE APPROX 5 NM. AT THE SAME TIME SCEL APCH WANTED TO KNOW WHY ALMOST EVERY 767 WAS OFF COURSE. I CONFIRMED THE DEVIATION AND CORRECTED BACK ON, SUBSEQUENTLY DISREGARDING THE MAP AND COMPLETING THE REST OF THE ARR AND CAT III AUTOLAND WITH NO FURTHER PROBS USING RAW DATA. CAUSING FACTORS: BRIEFING SHOULD BE COMPLETED PRIOR TO DSCNT. RECOMMEND PF TO BE ON RAW DATA DURING THE DSCNT USING THE MAP AS A BACKUP ESPECIALLY IN IMC CONDITIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE INFO RELATED TO THE POSSIBILITY OF A MAP SHIFT IS ON A COMPANY CHART. THE PAGE DOES NOT STATED WHERE IT OCCURS. RPTR IS OF THE OPINION THAT IT OCCURS BECAUSE OF THE HIGH SURROUNDING TERRAIN. ONCE THE ACFT APCHS AND PASSES TBN VORTAC THE IRU UPDATES THE MAP POS. THE TERRAIN TO THE E WHEN 40 MILES OUT IS ANYWHERE FROM 15,000 FT TO 20,000 FT HIGH. THE APCH CTLRS ARE VERY GOOD AT MONITORING THE ACFTS PROGRESS. THE 767'S WERE OFF COURSE MORE THAT DAY THAN USUAL. ON THE GND THE RPTR TALKED WITH CREWS OF OTHER U.S. CARRIERS AND THEY ALL NOTED THE MAP SHIFT. HE DOESN'T KNOW IF THEIR COMPANY POLICY REQUIRES MONITORING OF THE RAW DATA AS HIS COMPANY DOES. HE FEELS THAT A NOTE ON THE ARR PAGE, AS WELL AS THE PRESENT NOTE ON ARPT CHART IS WARRANTED REGARDING THE NEED TO MONITOR AND NAVIGATE BY THE RAW DATA BECAUSE OF MAP SHIFTS NORTH OF TBN.

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.