Narrative:

Performing an autoland to runway 07R at anc involves a recurrent anomaly as follows: aircraft not in check status or mechanical deficiency. Airport/runway has no reported deficiencies. Aircraft configured flaps 50; FMS speed and 'stable' at 5 miles from touchdown. Aircraft tracking/corrected as needed inbound on the localizer and glide when intercepted. Airport weather-winds calm.anomaly:approaching runway 07R at approximately 500 feet above touchdown as seen visually the aircraft will begin to drift off the extended centerline to the right. This is verified by raw data on the localizer CDI. The autopilot will do nothing to correct and return to the centerline course and if allowed to continue aircraft will touchdown right of the centerline of the runway uncomfortably so. Then; once the nose gear touches down the aircraft/autopilot will aggressively return to the centerline and begin tracking; this on a dry runway-one of my several concerns is how will the aircraft do on a contaminated runway with 'less than good braking action' measured?there is no interference in the critical area of the GS or localizer antennas on the ground. No preceding aircraft; ground vehicle traffic; wildlife visible or equipment failure reported from the tower cab. There is a problem either unique to or a combination of airway facilities; aircraft type and the runway topography as the approach end of the runway has such an aggressive slope that it may be deflecting the localizer signal. This description is what occurred on this flight/this date and is also a narrative of what has occurred on numerous other approaches to this runway using this procedure.runway topography and slope of touchdown zone. Surrounding runway topography causing multi-path signals. No other suggestion for possible causal explanation but my experience is definitive and repeatable. I understand that recent adjustments have been made to the ground based airways facility equipment and a subsequent FAA flight check performed but I wonder if this may be unique to the MD11 architecture and suggest a follow up/flight test in the MD11 along with pireps from [different aircraft we operate] in the meanwhile to verify this is or is not unique to the MD11.

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Original NASA ASRS Text

Title: MD11 Captain reported that the autopilot drifted to the right of the centerline at ANC airport when performing an autoland approach.

Narrative: Performing an autoland to Runway 07R at ANC involves a recurrent anomaly as follows: Aircraft not in check status or mechanical deficiency. Airport/Runway has no reported deficiencies. Aircraft configured Flaps 50; FMS Speed and 'Stable' at 5 miles from touchdown. Aircraft tracking/corrected as needed inbound on the Localizer and Glide when intercepted. Airport Weather-winds calm.Anomaly:Approaching Runway 07R at approximately 500 feet above touchdown as seen visually the aircraft will begin to drift off the extended centerline to the right. This is verified by Raw Data on the localizer CDI. The Autopilot will do nothing to correct and return to the centerline course and if allowed to continue aircraft will touchdown right of the centerline of the runway uncomfortably so. Then; once the nose gear touches down the aircraft/autopilot will aggressively return to the centerline and begin tracking; this on a dry runway-one of my several concerns is how will the aircraft do on a contaminated runway with 'less than good braking action' measured?There is no interference in the critical area of the GS or Localizer Antennas on the ground. No preceding aircraft; ground vehicle traffic; wildlife visible or equipment failure reported from the tower cab. There is a problem either unique to or a combination of airway facilities; aircraft type and the runway topography as the approach end of the runway has such an aggressive slope that it may be deflecting the localizer signal. This description is what occurred on this flight/this date and is also a narrative of what has occurred on numerous other approaches to this runway using this procedure.Runway topography and slope of touchdown zone. Surrounding Runway Topography causing multi-path signals. No other suggestion for possible causal explanation but my experience is definitive and repeatable. I understand that recent adjustments have been made to the ground based airways facility equipment and a subsequent FAA flight check performed but I wonder if this may be unique to the MD11 architecture and suggest a follow up/flight test in the MD11 along with PIREPs from [different aircraft we operate] in the meanwhile to verify this is or is not unique to the MD11.

Data retrieved from NASA's ASRS site 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.