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An erj pilot reported that in the navigation mode the aircraft s-turned while following the ind 23L localizer oscillations between 10 and 20 miles; but stabilized in the heading mode. The localizer oscillations ceased inside zerox.
| Attributes | |
| ACN | 1151783 |
| Time | |
| Date | 201402 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | IND.Airport |
| State Reference | IN |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | Medium Transport Low Wing 2 Turbojet Eng |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | ILS/VOR |
| Person 1 | |
| Function | Captain Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | ATC Issue All Types Deviation - Track / Heading All Types |
Narrative:
The flight was cleared to intercept the [runway] 23L localizer between clang and isola. We had a positive localizer identification and a stable reception of localizer and glideslope. The localizer needle seemed to be stable at first. No oscillations were noted before interception. The FGC was set to the navigation mode. When the autopilot captured the localizer; the localizer needle started to fluctuate about 2-3 degrees either side of the approach course and the autopilot chased the needle resulting in continuous large s-turns on the final between 20 and 10 miles. The pilot flying switched to heading mode to dampen the oscillations. The localizer needle was stable once inside the zerox FAF. The glideslope was stable the whole time. I have no suggestions how to fix the localizer oscillation problems.
Original NASA ASRS Text
Title: An ERJ pilot reported that in the NAV Mode the aircraft S-turned while following the IND 23L localizer oscillations between 10 and 20 miles; but stabilized in the Heading Mode. The localizer oscillations ceased inside ZEROX.
Narrative: The flight was cleared to intercept the [Runway] 23L localizer between CLANG and ISOLA. We had a positive localizer ID and a stable reception of localizer and glideslope. The localizer needle seemed to be stable at first. No oscillations were noted before interception. The FGC was set to the NAV mode. When the autopilot captured the localizer; the localizer needle started to fluctuate about 2-3 degrees either side of the approach course and the autopilot chased the needle resulting in continuous large S-turns on the final between 20 and 10 miles. The pilot flying switched to HDG mode to dampen the oscillations. The localizer needle was stable once inside the ZEROX FAF. The glideslope was stable the whole time. I have no suggestions how to fix the localizer oscillation problems.
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.