# SDR ASAA2023052343342

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: May 23, 2023
- Submitted: May 25, 2023
- Operation: Air carrier
- Aircraft: [N492AS](https://openairdocs.org/aircraft/N492AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 44110
- Aircraft time: 27,718 hours, 8,713 cycles
- System (JASC): [3600 · Pneumatic System](https://openairdocs.org/jasc/3600)
- Part: Unknown
- Part number: UNKNOWN
- Condition: Unknown
- Location: Unknown
- Stage of operation: NR
- How discovered: V
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2023052343342

## Discrepancy

ISOLATION VALVE DOES NOT OPEN WHEN SELECTED. APPEARS TO OPERATE CORRECTLY IN "AUTO"(BOTH PACKS IN AUTO, BOTH ENGINES AND APU BLEED ON, R DUCT PRESS &0 WITH ISOL OPEN. GROUNDED - YES. VERIFIED PILOT'S DISCREPANCY. VALVE DOESN'T OPEN INTERMITTENTLY, BUT WORKS IN AUTO & CLOSES CONSISTENTLY. SUSPECT ISOLATION VALVE STICKS INTERMITTENTLY. PERFORMED B737-900 FIM 36-10 TASK 806 INITAL EVAL. NO FAULT NOTED.

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