# SDR CHIR2018041000001

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: March 26, 2018
- Submitted: April 11, 2018
- Operation: Air carrier
- Filed by: [Columbia Helicopters, Inc, repair station CHIR823C](https://openairdocs.org/faa-repair-station/CHIR823C/columbia-helicopters-inc.md) (OpenAirDocs)
- Aircraft: [N188CH](https://openairdocs.org/aircraft/N188CH), registered now
- Make and model: Boeing 1072
- Aircraft serial: 107
- Aircraft time: 72,928 hours
- System (JASC): [6320 · Main Rotor Gearbox](https://openairdocs.org/jasc/6320)
- Part: Idler Assy
- Condition: Worn
- Location: Mr Transmission
- Part time: 4,057 hours
- Component: Transmission, Boeing
- Component part number: 107D201037
- Stage of operation: UK
- How discovered: O
- Nature of condition: O
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/CHIR2018041000001

## Discrepancy

DURING COAST DOWN AT THE END OF DAY, HEARD AN ABNORMAL CLICKING NOISE COMING FROM THE NR 1 HIGH SPEED SHAFT. THE PILOTS REPORTED THE NR 1 NF STAYED WITH THE NR DURING COAST DOWN WHILE NR 2 NF INDICATION SPLIT OFF. ON FURTHER INVESTIGATION, FOUND THE NR 1 CLUTCH FAILED TO DISENGAGE. REMOVED AND REPLACED THE XMSN AND RETURNED THE A/C BACK TO SERVICE. DURING INSPECTION OF IDLER HUBS, FOUND PINION SPURS AND IDLER HUBS WERE WORN AND WERE OUT OF TOLERANCE. CLUTCHES AND ASSOCIATED ARTICLES SCRAPPED DUE TO WEAR.

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