# SDR AALA201905199006

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: May 18, 2019
- Submitted: May 21, 2019
- Operation: Air carrier
- Aircraft: [N501AA](https://openairdocs.org/aircraft/N501AA), registered now
- Make and model: Doug DC-9-82
- Registry model: [Doug DC-9-82](https://openairdocs.org/model/mcdonnell-douglas-dc-9-82) (OpenAirDocs)
- Aircraft serial: 49738
- Aircraft time: 81,866 hours, 43,964 cycles
- System (JASC): [3421 · Attitude Gyro and Indicating System](https://openairdocs.org/jasc/3421)
- Part: Gyro
- Part serial: 88076598
- Condition: Faulty
- Location: Zone 100
- Stage of operation: DE
- How discovered: O
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/AALA201905199006

## Discrepancy

AIRCRAFT WAS GROUNDED: PILOT REPORTS INTERMITTENT AUTOPILOT PITCH MOVEMENT TWITCHING IN SMOOTH LEVEL FLIGHT. NOTE: UPON DESCENT FD BARS & AIRCRAFT (GOLD TRIANGLE SYMBOL) STAYED TOGETHER BUT PITCHED UP & DOWN RELATIVE TO THE HORIZON AND AUTOPILOT FOLLOWED THIS INSTRUMENT MOVEMENT ON CA PFD ONLY AUTOPILOT WAS  CONNECTED TO F.O. SIDE AND ALTHOUGH AUTOPILOT PITCH WAS OSCILLATING THE F/O/ PFD WAS STABLE. MAINTENANCE FOUND MULTIPLE ATTITUDE 1 SIGNAL FAULTS ON BOTH DFGCS DURING FAULT REVIEW. REPLACED THE #1 VERTICAL GYRO IAW AMM 34-23-01. OPS TEST GOOD.

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