A B767 crew experienced a navigation equipment deviation while on a 33 mi final.

Attributes
ACN	512585
Time
Date	200105
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	intersection : arnes
State Reference	CA
Altitude	msl single value : 10000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sct.tracon
Operator	common carrier : air carrier
Make Model Name	B767 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	arrival star : civet
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 230 flight time total : 17000 flight time type : 2151
ASRS Report	512585
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance non adherence : published procedure other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : returned to intended or assigned course flight crew : overrode automation
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

As we approached arnes intersection on the civet arrival, we had a map shift of about 1/4 mi to the right or north. The autoplt was on and it was in LNAV and flight level change descending. The autoplt rolled into a right turn to follow the new shifted track as we determined if the localizer was correct or the map. As the localizer went 1 DOT right of course, we turned off the autoplt and turned back to the center of the localizer. We both turned to the ILS mode to complete the civet with localizer and DME only. As we turned back, ATC said they showed us to the right of center and asked if we were correcting. We said we were. As we approached the FAF, I checked the map and it had corrected back to normal. But I think it remained shifted for about 2 mins. After landing, I called the approach control on the telephone and he said it had not caused any conflict. He did tell me though that air carrier had a problem with their B757 a while ago. Just as they would hit the arnes intersection, their map would shift left and the airplanes would start a turn to the left. We also told a mechanic and put this information in the aircraft logbook.

Original NASA ASRS Text

Title: A B767 CREW EXPERIENCED A NAV EQUIP DEV WHILE ON A 33 MI FINAL.

Narrative: AS WE APCHED ARNES INTXN ON THE CIVET ARR, WE HAD A MAP SHIFT OF ABOUT 1/4 MI TO THE R OR N. THE AUTOPLT WAS ON AND IT WAS IN LNAV AND FLT LEVEL CHANGE DSNDING. THE AUTOPLT ROLLED INTO A R TURN TO FOLLOW THE NEW SHIFTED TRACK AS WE DETERMINED IF THE LOC WAS CORRECT OR THE MAP. AS THE LOC WENT 1 DOT R OF COURSE, WE TURNED OFF THE AUTOPLT AND TURNED BACK TO THE CTR OF THE LOC. WE BOTH TURNED TO THE ILS MODE TO COMPLETE THE CIVET WITH LOC AND DME ONLY. AS WE TURNED BACK, ATC SAID THEY SHOWED US TO THE R OF CTR AND ASKED IF WE WERE CORRECTING. WE SAID WE WERE. AS WE APCHED THE FAF, I CHKED THE MAP AND IT HAD CORRECTED BACK TO NORMAL. BUT I THINK IT REMAINED SHIFTED FOR ABOUT 2 MINS. AFTER LNDG, I CALLED THE APCH CTL ON THE TELEPHONE AND HE SAID IT HAD NOT CAUSED ANY CONFLICT. HE DID TELL ME THOUGH THAT ACR HAD A PROB WITH THEIR B757 A WHILE AGO. JUST AS THEY WOULD HIT THE ARNES INTXN, THEIR MAP WOULD SHIFT L AND THE AIRPLANES WOULD START A TURN TO THE L. WE ALSO TOLD A MECH AND PUT THIS INFO IN THE ACFT LOGBOOK.

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.