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A B737-300 flight crew was surprised when the autoflight system initiated a hard right turn during an arrival sequencing.
| Attributes | |
| ACN | 897215 |
| Time | |
| Date | 201007 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.ARTCC |
| State Reference | US |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | FMS/FMC |
| Person 1 | |
| Function | First Officer |
| Experience | Flight Crew Last 90 Days 230 Flight Crew Type 6000 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Track / Heading All Types |
Narrative:
We were on our fourth arrival into the airport because of weather and changing runways. We were coming from the southwest heading about 050 toward a fix on the arrival. The aircraft started to turn sharply to the right nine miles before we reached the fix. The number two FMC blanked out just before this; but came back with no errors. We thought the plane was unsure of its position. The captain went to cws and turned the plane back towards our original heading. I told ATC we were having navigation problems and they gave us a heading. After talking about it; we decided the plane needed to start the turn nine miles out because of our ground speed and the large heading change (about 120 degrees). If we had glass in the plane; it would not have been a problem.
Original NASA ASRS Text
Title: A B737-300 flight crew was surprised when the autoflight system initiated a hard right turn during an arrival sequencing.
Narrative: We were on our fourth arrival into the airport because of weather and changing runways. We were coming from the southwest heading about 050 toward a fix on the arrival. The aircraft started to turn sharply to the right nine miles before we reached the fix. The number two FMC blanked out just before this; but came back with no errors. We thought the plane was unsure of its position. The Captain went to CWS and turned the plane back towards our original heading. I told ATC we were having navigation problems and they gave us a heading. After talking about it; we decided the plane needed to start the turn nine miles out because of our ground speed and the large heading change (about 120 degrees). If we had glass in the plane; it would not have been a problem.
Data retrieved from NASA's ASRS site as of April 2012 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.