Master Switches

Cessna Model 172S Skyhawk SPArcing Avionics MasterPilot reported burning smell and failure of avionics #2 buss during run-up. Troubleshooting revealed the right side of the avionics master switch (#2 buss) had been arcing internally. Replaced switch; ops check okay.

Editorial Staff

Sunday, November 19, 2017 at 12:00 AM ET

Verified

Key Takeaways:

Master and avionics master switches are prone to various failures across different aircraft models.
Observed failure modes include internal arcing, corrosion, manufacturing defects, and intermittent or sticking operation.
These malfunctions can lead to critical issues such as loss of avionics, damaged components, burning smells, or impaired aircraft system control.

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Cessna Model 172S Skyhawk SP
Arcing Avionics Master

Pilot reported burning smell and failure of avionics #2 buss during run-up. Troubleshooting revealed the right side of the avionics master switch (#2 buss) had been arcing internally. Replaced switch; ops check okay.
Part total time: 1018.0 hours