# SDR ASAA2019041979042

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: April 17, 2019
- Submitted: April 20, 2019
- Operation: Air carrier
- Aircraft: [N448AS](https://openairdocs.org/aircraft/N448AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 36356
- Aircraft time: 12,266 hours, 4,048 cycles
- System (JASC): [2150 · Cabin Cooling System](https://openairdocs.org/jasc/2150)
- Part: Control Valve
- Condition: Failed
- Location: Lt A/C Pack
- Part time: 44,016 hours, 14,438 cycles
- Stage of operation: CR
- How discovered: O
- Nature of condition: O
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2019041979042

## Discrepancy

LEVEL AT CRUISE AT 34000 THE CABIN CLIMB GUAGE SHOWED +/- 500 FPM. LEFT DUCT PRESSURE FLUCTUATED FROM 45/40 PSI. R DUC WAS STEADY AT 45 PSI. LEVEL AT 24000 CABIN CLIMB SHOWED +/- 300 FPM. GROUNDED - YES. DURING CHECK FOUND #1 TCV FLUCTUATING (OPEN/CLOSE) CAUSING +/- 200 FPM CABIN ALTITUDE REF FIM 21-33 TASK 802. REMOVED AND REPLACED L/H PACK TCV REF B737-900 AMM 21-51-10. OPS AND BITE CK GOOD. NO LEAKS. NO FAULTS ON DCPC #1 OR #2. REPEATED AIRCRAFT CABIN LEAK CKS REF AMM 05-51-91. NO LEAKS. OPS CKS GOOD. NO CABIN ALT RATE FLUCTUATIONS.

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