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B737 flight crew; during an ILS approach; compared the FMS guidance to the ILS localizer guidance and show a deviation of approximately one third mi difference on the FMS track.
| Attributes | |
| ACN | 688932 |
| Time | |
| Date | 200602 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : fai.airport |
| State Reference | AK |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Controlling Facilities | tracon : fai.tracon tower : fai.tower |
| Operator | common carrier : air carrier |
| Make Model Name | B737-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| ASRS Report | 688932 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | aircraft equipment problem : less severe other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : fmc/ils/loc other flight crewa other flight crewb |
| Resolutory Action | none taken : anomaly accepted |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Aircraft |
| Primary Problem | Aircraft |
Narrative:
This is a second report on the same type event at the same location. On visual approach to fai runway 1L ILS we saw a map shift event. We did a straight-in approach from more than 20 mi out using the ILS for guidance. We pulled up the approach from the database and did not modify it at all. The initial fix on the approach was a centerline fix about 4-5 mi before cache. Between the first fix and cache; the FMS showed us .3 NM left of course when the localizer was centered. The anp was .05 to .04. The error showed all the way down to the runway (our track showed us landing beside the runway). The report I made about the same type event that occurred was in aircraft XXX. We had used that airplane all day through southeast including rnp approachs with no errors noted. It seems the discrepancy is in the coded approach to fai.
Original NASA ASRS Text
Title: B737 FLT CREW; DURING AN ILS APCH; COMPARED THE FMS GUIDANCE TO THE ILS LOC GUIDANCE AND SHOW A DEV OF APPROX ONE THIRD MI DIFFERENCE ON THE FMS TRACK.
Narrative: THIS IS A SECOND RPT ON THE SAME TYPE EVENT AT THE SAME LOCATION. ON VISUAL APCH TO FAI RWY 1L ILS WE SAW A MAP SHIFT EVENT. WE DID A STRAIGHT-IN APCH FROM MORE THAN 20 MI OUT USING THE ILS FOR GUIDANCE. WE PULLED UP THE APCH FROM THE DATABASE AND DID NOT MODIFY IT AT ALL. THE INITIAL FIX ON THE APCH WAS A CTRLINE FIX ABOUT 4-5 MI BEFORE CACHE. BTWN THE FIRST FIX AND CACHE; THE FMS SHOWED US .3 NM L OF COURSE WHEN THE LOC WAS CTRED. THE ANP WAS .05 TO .04. THE ERROR SHOWED ALL THE WAY DOWN TO THE RWY (OUR TRACK SHOWED US LNDG BESIDE THE RWY). THE RPT I MADE ABOUT THE SAME TYPE EVENT THAT OCCURRED WAS IN ACFT XXX. WE HAD USED THAT AIRPLANE ALL DAY THROUGH SE INCLUDING RNP APCHS WITH NO ERRORS NOTED. IT SEEMS THE DISCREPANCY IS IN THE CODED APCH TO FAI.
Data retrieved from NASA's ASRS site as of January 2009 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.