# SDR DALA2018081765126

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: August 15, 2018
- Submitted: August 17, 2018
- Operation: Air carrier
- Aircraft: [N721TW](https://openairdocs.org/aircraft/N721TW), registered now
- Make and model: Boeing 757231
- Aircraft serial: 29954
- Aircraft time: 69,887 hours, 18,738 cycles
- System (JASC): [2130 · Cabin Pressure Control System](https://openairdocs.org/jasc/2130)
- Part: Check Valve
- Condition: Failed
- Stage of operation: CR
- How discovered: O
- Nature of condition: J
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/DALA2018081765126

## Discrepancy

LOST PRESSURIZATION AT FL 340, 2 HOURS. INTO FLIGHT UNCOMMANDED. CABIN ALTITUDE 10,000, DIFFERENTIAL 6.2, SHORTLY AFTERWARD RED CABIN ALTITUDE EICAS. OXYGEN MASKS DONNED AND AIRCRAFT FLOWN TO 10,000 FT. AIRCRAFT PRESSURE CLIMBED AND DESCENDED +/- 2,000 FT WHILE LEVEL. CABIN CLIMBED 1,000 FT/MIN WHILE DESCENDING OUT OF 10,000. WAS UNABLE TO CLOSE THE OUTFLOW VALVE MANUALLY ONLY TO 90%.  TROUBLESHOT IAW NO GO ODI 2132. FOUND CLAMP DETACHED ON THE LT PACK OUTLET, CHECK VALVE LEAKING, AND B-NUT LOOSEON REHEATER LINE. TIGHTENED BOTH IAW AMM 20-11-00. BITE TESTED BOTH CPC IAW AMM 21-30-00-815-002, LOW INFLOW FAULT. LEFT PACK CHECK VALVE FAILED. R & R THE CHECK VALVE IAW AMM 21-51-1, PB401. R & R TWO PRESSURE CONTROLLERS IAW  AMM 21-51-00-755-622 WITH NO FAULTS. EXCESSIVE CABIN PRESSURE LEAKAGE CHECKED IAW AMM 05-51-24. LEAKS WITHIN LIMITS. AIRCRAFT OK FOR SERVICE.

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