# SDR UPS804364

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: September 6, 1995
- Submitted: March 26, 2000
- Operation: Air carrier
- Aircraft: [N422UP](https://openairdocs.org/aircraft/N422UP), registered now
- Make and model: Boeing 757-24APF
- Registry model: [Boeing 757-24APF](https://openairdocs.org/model/boeing-757-24apf) (OpenAirDocs)
- Aircraft serial: 25324
- System (JASC): [4900 · Airborne Auxiliary Power Unit (APU) System](https://openairdocs.org/jasc/4900)
- Part: Apu
- Condition: Malfunction
- Location: Empennage
- Stage of operation: CL
- Nature of condition: J
- Precautionary procedure: A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/UPS804364

## Discrepancy

PILOT REPORTED, A/C DID AIR TURNBACK DUE TO APU AUTO-SHUTDOWN IN FLIGHT.  THIS LEFT A/C WITH ONLY ONE OPERATING GENERATOR DUE TO LEFT ENGINE GENERATOR BEING ON DEFERRAL (M-97875).  BITE CHECKED APU, FOUND REVERSE FLOW SHUTDOWN FAULT WITH NO LRU FAULTS.  REPLACED LEFT ENG IDG IAW MM 24-11-1, OPS CKS OK AND THIS CLEARED M 97875.  REPLACED APU SURGE BLEED VALVE IAW MM 49-53-1 AND APU FLOW SENSOR MODULE IAW MM 49-53-8, OPS CHECKS OK.

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