# SDR BB07065

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: August 14, 2007
- Submitted: August 16, 2007
- Operation: Air carrier
- Aircraft: N205UW
- Make and model: Boeing 757-23N
- Registry model: [Boeing 757-23N](https://openairdocs.org/model/boeing-757-23n) (OpenAirDocs)
- Aircraft serial: 30887
- Aircraft time: 21,175 hours, 6,714 cycles
- System (JASC): [4900 · Airborne Auxiliary Power Unit (APU) System](https://openairdocs.org/jasc/4900)
- Part: Check Valve
- Part number: 32021303
- Part serial: 2500
- Condition: Chattering
- Location: Apu
- Part time: 2,324 hours, 718 cycles
- Stage of operation: CR
- How discovered: O
- Nature of condition: O
- Precautionary procedure: A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/BB07065

## Discrepancy

FLIGHT 728, PHL-GLA:  CREW REPORTED A RHYTHMIC KNOCKING SOUND IN THE AREA OF SEAT 13A.  FLIGHT RETURNED TO PHL.  MAINTENANCE REPLACED THE APU CHECK VALVE.

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