# SDR 9JLA2021040510262

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: March 30, 2021
- Submitted: April 5, 2021
- Operation: Air carrier
- Aircraft: [N561MT](https://openairdocs.org/aircraft/N561MT), registered now
- Make and model: Cessna 560CESSNA
- Aircraft serial: 5600122
- Aircraft time: 8,424 hours, 7,723 cycles
- System (JASC): [3200 · Landing Gear System](https://openairdocs.org/jasc/3200)
- Part: Relay
- Part number: 71226
- Condition: Defective
- Stage of operation: IN
- How discovered: 9
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/9JLA2021040510262

## Discrepancy

THE FLIGHT CREW REPORTED THAT THE ROTARY TEST SWITCH FAILED TO TEST THE LANDING GEAR SYSTEM CAUSING THE FLIGHT TO BE CANCELLED. THE MAINTENANCE VENDOR TROUBLESHOT AND DISCOVERED A DEFECTIVE K78 RELAY ON PCB101. THE MAINTENANCE VENDOR REPLACED THE K78 RELAY WITH NEW. OPERATIONAL CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.

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