# SDR ASAA2023061533562

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: June 13, 2023
- Submitted: June 15, 2023
- Operation: Air carrier
- Aircraft: [N531AS](https://openairdocs.org/aircraft/N531AS), registered now
- Make and model: Boeing 737890
- Aircraft serial: 35199
- Aircraft time: 45,956 hours, 13,338 cycles
- System (JASC): [3400 · Navigation System](https://openairdocs.org/jasc/3400)
- Part: Unknown
- Part number: UNKNOWN
- Condition: Unknown
- Location: Unknown
- Stage of operation: CR
- How discovered: V
- Nature of condition: J
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2023061533562

## Discrepancy

AT CRUISE FO HAD VTRK DISPLAYED ON ND DISPLAY AND AUTOPILOT REVERTED TO CWS ROLL MODE. VTRK WENT AWAY AND OPS WENT BACK TO NORMAL. GROUNDED - YES. VERIFIED FMC+DFCS FAULTS FOR FMC DATA INVALID AND PRES POS LAT RATE. NO OTHER OCCURRENCES PREVIOUS FLT LEGS. DFCS BITE, FMC BITE CHKS GOOD REF B737-800 FIMS 22-11-801 & 34-61-801. VERIFIED ADIRU-L AND -R BITE CHKS GOOD AND NO FAULTS REF FIM 34-21-801.

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