# SDR AALA201912169044

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: December 12, 2019
- Submitted: December 16, 2019
- Operation: Air carrier
- Aircraft: [N923NN](https://openairdocs.org/aircraft/N923NN), registered now
- Make and model: Boeing 737823
- Aircraft serial: 31167
- Aircraft time: 21,555 hours, 8,747 cycles
- System (JASC): [3420 · Attitude and Direction Data System](https://openairdocs.org/jasc/3420)
- Part: Adiru
- Part number: HG2050ACXX
- Part serial: 56057154
- Condition: Faulty
- Stage of operation: DE
- How discovered: O
- Nature of condition: J
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/AALA201912169044

## Discrepancy

AIRCRAFT WAS GROUNDED: PILOT REPORTS ON DESCENT, FMC MESSAGE- IR5-L DRIFT THEN VERIFY POSITION LEFT PFD TUMBLED AND HEADING WAS  INCORRECT. FINALLY THE LEFT IRS FAULT LIGHT ILLUMINATED. ON FINAL AIRSPEED LOW WARNINGS. THE  F/O INSTRUMENTS WERE NORMAL THROUGHOUT. MAINTENANCE REMOVED AND REPLACED LEFT AIR DATA INERTIAL REFERENCE UNIT IAW AMM 34-21-01 . OPS CHECKS GOOD.

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