# SDR 99ZZZX4536

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: October 29, 1999
- Submitted: March 26, 2000
- Operation: Air carrier
- Aircraft: [N317TT](https://openairdocs.org/aircraft/N317TT), registered now
- Make and model: Lear 35A
- Registry model: [Lear 35A](https://openairdocs.org/model/gates-learjet-35a) (OpenAirDocs)
- Aircraft serial: 317
- System (JASC): [2133 · Pressure Regulator/Outflow Valve](https://openairdocs.org/jasc/2133)
- Part: Valve
- Part number: 1304061
- Condition: Cracked
- Location: Fuselage
- Part time: 6,766 hours
- Component: Airesrch
- Stage of operation: IN
- Nature of condition: W
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/99ZZZX4536

## Discrepancy

AS A RESULT OF A RECENT PRESSURE VESSEL INSP, FOUND THE SAFETY VALVE, PN 130406-1, SN 121-2018, DATED 12-22-81 BY LEAR, WAS FOUND TO HAVE A CRACKED NR 1 BOSS.  BY DATE AND S/N, THIS VALVE IS NOT AFFECTED BY AD 95-20-03 (LEARJET SB 35-21-19).  TO LOCATE CRACK,  'AN' FITTING WAS REMOVED.  PRESSURIZATION SYS WAS WORKING NORMALLY, WITH NO INDICATION OF A CRACK. LEARJET CONFIRMED CRACKS NOT ACCEPTABLE AND VALVE REPLACED.  SINCE BOTH OUTFLOW VALVE AND SAFETY VALVE HAVE SAME P/N, BOTH VALVES WERE CHECKED.  NO CRACKS FOUND IN THE OUTFLOW VALVE.  CRACK WAS APPARENTLY CAUSED BY OVERTORQUE SITUATION, OR, OVER A PERIOD OF TIME, CAUSED BY EXTREME TEMP CHANGES.  SUBMITTER SUSPECTED OVERTQORQUE POSSIBILITY FIRST.

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