Narrative:

This report is about a lateral deviation during ILS approach into shanghai due to temporary loss of localizer signal. I was the pilot flying and captain was pilot not flying. We were vectored to ILS 17R final approach course by shanghai approach. Shanghai was using runway 17R (west side) and [runway] 16 (east side) for arrivals. I was flying with the autopilot and autothrottles on; and intercepted the localizer at about 15 NM. The captain called 'established on localizer' to approach and were then cleared the ILS 17R into shanghai. Weather was VMC with scattered clouds at approximately 1;500 ft and approximately 5 miles visibility. At approximately 8 NM; I noticed the flight director commanded a slight right turn off our course and noticed that my localizer indicator became erratic. As I said to the captain that the localizer looks bad; the flight director commanded a slight turn left back to course; the flight director appeared to be making an appropriate correction. As the aircraft rolled left; the flight director commanded more left bank; as my localizer remained erratic. As the aircraft rolled through approximately 10 degrees of left bank passing our course to the left; I disconnected the autopilot and began to roll back to the right. At this point we were slightly left of course moving left of course. As I rolled the aircraft back to the right; I asked the captain to select runway heading for the flight director. Just as I rolled out with a slight intercept heading back to localizer course; shanghai approach asked us to 'confirm we were established on ILS'; the captain responded that we lost the localizer signal and were correcting back to course. The localizer was beginning to settle down and appeared to intermittently indicate 1 dot left of course. The captain then said he had runway in sight (using efvs) and called for control of the airplane to align us quicker. I transferred control to him and he aligned the aircraft visually with the runway until I visually acquired the runway at approximately 4 NM. The localizer signal now appeared to be valid. Remainder of approach and landing were uneventful. Based on my sa we had negligible amount of lateral deviation right of course and deviated a little more than 1 dot left of course at approximately 6 to 7 NM. I allowed the autopilot to remain engaged with the erratic localizer indication for too long. Once I noticed that the localizer was erratic; I should have disconnected the autopilot immediately to prevent any erratic flight director commands. Although; the flight director appeared initially to be correcting for the deviation; the localizer was still erratic and I should have downgraded automation immediately. Then; we could have reported loss of localizer and asked for vectors to visual approach.

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Original NASA ASRS Text

Title: Air Carrier First Officer experiences an erratic LOC signal during approach to ZSPD and allows the aircraft to drift left of course before turning off the autopilot. The aircraft is realigned with the runway visually and the LOC signal becomes stronger as the approach continues.

Narrative: This report is about a lateral deviation during ILS approach into Shanghai due to temporary loss of localizer signal. I was the pilot flying and Captain was pilot not flying. We were vectored to ILS 17R final approach course by Shanghai Approach. Shanghai was using Runway 17R (west side) and [Runway] 16 (east side) for arrivals. I was flying with the autopilot and autothrottles on; and intercepted the localizer at about 15 NM. The Captain called 'established on localizer' to approach and were then cleared the ILS 17R into Shanghai. Weather was VMC with scattered clouds at approximately 1;500 FT and approximately 5 miles visibility. At approximately 8 NM; I noticed the flight director commanded a slight right turn off our course and noticed that my localizer indicator became erratic. As I said to the Captain that the localizer looks bad; the flight director commanded a slight turn left back to course; the flight director appeared to be making an appropriate correction. As the aircraft rolled left; the flight director commanded more left bank; as my localizer remained erratic. As the aircraft rolled through approximately 10 degrees of left bank passing our course to the left; I disconnected the autopilot and began to roll back to the right. At this point we were slightly left of course moving left of course. As I rolled the aircraft back to the right; I asked the Captain to select runway heading for the flight director. Just as I rolled out with a slight intercept heading back to localizer course; Shanghai Approach asked us to 'confirm we were established on ILS'; the Captain responded that we lost the localizer signal and were correcting back to course. The localizer was beginning to settle down and appeared to intermittently indicate 1 dot left of course. The Captain then said he had runway in sight (using EFVS) and called for control of the airplane to align us quicker. I transferred control to him and he aligned the aircraft visually with the runway until I visually acquired the runway at approximately 4 NM. The localizer signal now appeared to be valid. Remainder of approach and landing were uneventful. Based on my SA we had negligible amount of lateral deviation right of course and deviated a little more than 1 dot left of course at approximately 6 to 7 NM. I allowed the autopilot to remain engaged with the erratic localizer indication for too long. Once I noticed that the localizer was erratic; I should have disconnected the autopilot immediately to prevent any erratic flight director commands. Although; the flight director appeared initially to be correcting for the deviation; the localizer was still erratic and I should have downgraded automation immediately. Then; we could have reported loss of localizer and asked for vectors to visual approach.

Data retrieved from NASA's ASRS site as of July 2013 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.