# SDR UALA2009112503664

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: November 25, 2009
- Submitted: November 25, 2009
- Operation: Air carrier
- Aircraft: [N120UA](https://openairdocs.org/aircraft/N120UA), registered now
- Make and model: Boeing 747422
- Aircraft serial: 29166
- Aircraft time: 43,383 hours, 5,179 cycles
- Engine: Pwa PW4056
- System (JASC): [4900 · Airborne Auxiliary Power Unit (APU) System](https://openairdocs.org/jasc/4900)
- Part: Controller
- Part number: 77328918
- Part serial: 235
- Condition: Popped
- Location: Apu
- Stage of operation: CR
- How discovered: O
- Nature of condition: J
- Precautionary procedure: J, A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/UALA2009112503664

## Discrepancy

APU ELEC STANDBY CIRCUIT BREAKER POPPED, RTFL.  REPLACED THE NR 4 ENG HIGH PRESSURE CONTROLLER, NR 4 ENG PRESSURE REGULATING VALVE AND REPLACED THE NR 4 ENG PRESSURE REGULATING VALVE CONTROLLER.  ALSO, CHK'D THE SECURITY OF THE BLEED LINES.  ALL CHECKS ARE GOOD.  ACCOMPLISHED ENG RUN FOR PRV, PRV CONTROLLER AND HPC REPLACEMENT.  NO FAULTS NOTED.

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