# SDR P5CA2025101800093

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: October 18, 2025
- Submitted: October 20, 2025
- Operation: Air carrier
- Aircraft: [N858GT](https://openairdocs.org/aircraft/N858GT), registered now
- Make and model: Boeing 747-87UF
- Registry model: [Boeing 747-87UF](https://openairdocs.org/model/boeing-747-87uf) (OpenAirDocs)
- Aircraft serial: 37569
- Aircraft time: 59,356 hours, 9,237 cycles
- System (JASC): [2133 · Pressure Regulator/Outflow Valve](https://openairdocs.org/jasc/2133)
- Part: Outflow Valve
- Part number: 50E991
- Part serial: 515
- Condition: Faulted
- Location: Zone 100
- Stage of operation: CL
- How discovered: O
- Nature of condition: J
- Precautionary procedure: A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/P5CA2025101800093

## Discrepancy

AT FLT 310, CABIN PRESSURE BECAME UNCONTROLLABLE. OUTFLOW VALVES WERE INDICATING FULLY CLOSED. CABIN ALTITUDE WAS CLIMBING 200 FPM.(<P>COMPLETED THE FOLLOWING CHECKS PER BOEING SR: CABIN SYSTEM CONTROL PRESSURE TEST AMM TASK 21-31-00-735-011 AND EXCESSIVE CABIN PRESSURE LEAKAGE TEST PER AMM 05-51-08-702-001. PARTS REPLACED. REF AMM 21-26-15/401. R & R FWD CARGO OVERBOARD VALVE.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.