# SDR AALA202609061034

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: September 3, 2026
- Submitted: September 7, 2026
- Operation: Air carrier
- Aircraft: [N539UW](https://openairdocs.org/aircraft/N539UW), registered now
- Make and model: Airbus A321-231
- Registry model: [Airbus A321-231](https://openairdocs.org/model/airbus-a321-231) (OpenAirDocs)
- Aircraft serial: 4082
- Aircraft time: 52,405 hours, 21,108 cycles
- System (JASC): [4900 · Airborne Auxiliary Power Unit (APU) System](https://openairdocs.org/jasc/4900)
- Part: Pressure Switch
- Condition: Faulted
- Location: Zone 100
- Component: Apu, Hnywl, 1319A
- Component part number: 38007081
- Stage of operation: CL
- How discovered: O
- Nature of condition: H, J
- Precautionary procedure: A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/AALA202609061034

## Discrepancy

AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO DFW DUE TO THE FLIGHT CREW REPORTING WITH ENGINE 1 IDG INOPERATIVE AND ON MEL THE APU AUTO SHUTDOWN WHILE PASSING FL 290 - THE AIRCRAFFT LANDED SAFELY AT DFW WITHOUT FURTHER INCIDENT - MAINTENANCE FOUND AN APU OIL PRESSURE SWITCH FAULT MESSAGE ON THE MCDU AND REPLACED THE PRESSURE SWITCH PER AMM 49-94-14

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