# SDR IPXA2024120405940

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: December 3, 2024
- Submitted: December 4, 2024
- Operation: Air carrier
- Aircraft: [N475UP](https://openairdocs.org/aircraft/N475UP), registered now
- Make and model: Boeing 757-24APF
- Registry model: [Boeing 757-24APF](https://openairdocs.org/model/boeing-757-24apf) (OpenAirDocs)
- Aircraft serial: 28845
- Aircraft time: 23,094 hours, 15,736 cycles
- System (JASC): [2150 · Cabin Cooling System](https://openairdocs.org/jasc/2150)
- Part: A/C Pack
- Condition: Faulted
- Location: Zone 100
- Stage of operation: IN
- How discovered: V
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/IPXA2024120405940

## Discrepancy

VERY LOUD BUZZING NOISE FROM LEFT A/C PACK WHEN USING ENGINE BLEED AIR SOUND NOT PRESENT WHEN USING APU BLEED AIR. SOUND SEEMS TO COME FROM RIGHT SIDE GLARE SHIELD IN FRONT OF F/O. FOUND A LOW BUZZING NOISE WHEN RUNNING APU WITH RIGHT AND LEFT PACKS ON. FOUND NOISE TO BE COMING FROM NEAR F/O WINDOW SUNVISOR TRACK . FOUND LOOSE SCREW ON SUNVISOR TRACK. TIGHTENED SCREW PER AMM 20-11-00. NOISE APPEARS TO BE GONE.

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