# SDR 95ZZZX3001

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: May 20, 1995
- Submitted: March 26, 2000
- Operation: General aviation
- Aircraft: [N12885](https://openairdocs.org/aircraft/N12885), registered now
- Make and model: Cessna 172
- Registry model: [Cessna 172](https://openairdocs.org/model/cessna-172) (OpenAirDocs)
- Aircraft serial: 17262342
- System (JASC): [3416 · Altimeter, Barometric/Encoder](https://openairdocs.org/jasc/3416)
- Part: Encoder
- Part number: D120P2T
- Condition: Defective
- Location: Altimeter
- Component: Transcal
- Stage of operation: IN
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/95ZZZX3001

## Discrepancy

THERE WAS ZERO BACKLASH IN THE ENCODER MODULE GEAR MESH.  THE O/H MANUAL CALLS OUT ONE-QUARTER TO ONE-HALF TOOTH WIDTH BLACKLASH IN THIS MESH.  WHEN THE BACKLA SH IS ZERO, A VERY SLIGHT CHANGE IN TEMPERATURE CAN CAUSE THE ENCODER TO HANG UP.

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