# SDR SF20050721

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: July 21, 2005
- Submitted: July 22, 2005
- Operation: Air carrier
- Aircraft: [N123XS](https://openairdocs.org/aircraft/N123XS), registered now
- Make and model: Saab SF340A
- Registry model: [Saab SF340A](https://openairdocs.org/model/saab-scania-sf340a) (OpenAirDocs)
- Aircraft serial: 123
- System (JASC): [3417 · Air Data Computer](https://openairdocs.org/jasc/3417)
- Part: Adc
- Condition: Malfunctioned
- Location: Cockpit
- Stage of operation: CR
- How discovered: O
- Nature of condition: S
- Precautionary procedure: A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/SF20050721

## Discrepancy

FLIGHT 9003 FWA-DAY, PILOT CALLED ON THE RADIO REPORTING THE CAPTAIN'S ALTIMETER AND VERTICAL SPEED INDICATOR WERE FLUCTUATING 20-40 FT, CAUSING THE AUTO-PILOT TO FOLLOW WITH A PITCH UP AND DOWN FLUCTUATION. AIRCRAFT WAS TOLD TO RETURN TO FWA. AIR DATA COMPUTER WAS REPLACED.

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