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An air carrier MD80 flight crew experiences ILS localizer fluctuations during an approach to runway 4R at ord. When the preceding aircraft cleared the runway these fluctuations ceased.
| Attributes | |
| ACN | 430546 |
| Time | |
| Date | 199903 |
| Day | Tue |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : 01g.fss navaid : ifju.ils |
| State Reference | IL |
| Altitude | msl bound lower : 2200 msl bound upper : 3000 |
| Environment | |
| Flight Conditions | IMC |
| Weather Elements | Snow |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : c90.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Super 80 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 4r |
| Flight Phase | descent : approach |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | tower : ord.tower |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 4r |
| Flight Phase | descent : approach landing : roll |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : multi engine pilot : atp |
| ASRS Report | 430546 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | controller : local |
| Qualification | pilot : multi engine pilot : instrument pilot : commercial |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : ils and flight director course indicator other flight crewa |
| Resolutory Action | flight crew : overrode automation |
| Consequence | other |
| Supplementary | |
| Problem Areas | Airport |
| Primary Problem | Airport |
| Situations | |
| Navigational Aid | IFJU.ILS |
Narrative:
At 3000 ft on approach noticed localizer deflections of 1 1/2 DOT either side of center. Flight directors attempted to bracket this deflection during approach. Strongly suspect this deflection was caused by previous aircraft exiting the runway 4R. After aircraft cleared runway and at about the runway 4R OM, localizer deflections steadied. Completed manual approach as per air carrier operating specifications. Recommend we continue with advisory to crews prohibiting coupled approachs to runway 4R. WX was IFR, 1 1/2 mi visibility with snow showers. Ceiling approximately 500 ft.
Original NASA ASRS Text
Title: AN ACR MD80 FLC EXPERIENCES ILS LOC FLUCTUATIONS DURING AN APCH TO RWY 4R AT ORD. WHEN THE PRECEDING ACFT CLRED THE RWY THESE FLUCTUATIONS CEASED.
Narrative: AT 3000 FT ON APCH NOTICED LOC DEFLECTIONS OF 1 1/2 DOT EITHER SIDE OF CTR. FLT DIRECTORS ATTEMPTED TO BRACKET THIS DEFLECTION DURING APCH. STRONGLY SUSPECT THIS DEFLECTION WAS CAUSED BY PREVIOUS ACFT EXITING THE RWY 4R. AFTER ACFT CLRED RWY AND AT ABOUT THE RWY 4R OM, LOC DEFLECTIONS STEADIED. COMPLETED MANUAL APCH AS PER ACR OPERATING SPECS. RECOMMEND WE CONTINUE WITH ADVISORY TO CREWS PROHIBITING COUPLED APCHS TO RWY 4R. WX WAS IFR, 1 1/2 MI VISIBILITY WITH SNOW SHOWERS. CEILING APPROX 500 FT.
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.