# SDR BJNA090101

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: January 29, 2009
- Submitted: February 24, 2009
- Operation: Air carrier
- Aircraft: N43XA
- Make and model: Boeing 737-400
- Registry model: [Boeing 737-400](https://openairdocs.org/model/boeing-737-400) (OpenAirDocs)
- Aircraft serial: 24796
- System (JASC): [4920 · APU Core Engine](https://openairdocs.org/jasc/4920)
- Part: Apu
- Part number: GTCP85129J
- Part serial: P30557
- Condition: Overheated
- Stage of operation: CR
- How discovered: O
- Nature of condition: M, J
- Precautionary procedure: A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/BJNA090101

## Discrepancy

APU FIRE/OVHT LIGHT ILLUMINATED IN FLIGHT.  QRH/MEMORY ITEMS FOLLOWED, BOTTLE DISCHARGED, FIRE/OVHT LIGHT EXTINGUISHED.  INSPECTION FOUND HEAT DAMAGE TO OVHT/FIRE DETECTION WIRING AND POSSIBLE TURBINE WHEEL FAILURE.  REMOVED AND REPLACED APU.  FAILURE ANALYSIS - PROBABLE CAUSES ARE DEFECTIVE TEMPERATURE CONTROL SYS/ INCORRECT TURBINE BEARING SLEEVE INSTALLED, WHICH WOULD RESULT IN EXCESSIVE VIBRATION FOLLOWED BY CONTACT OF THE TURBINE WHEEL AND SHROUD.  (K)

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