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Magneto Checks

What you’re checking, and why, and doing them while airborne and when running lean of peak EGT.  

Gemini Sparkle

Key Takeaways:

  • Aircraft spark-ignition engines use self-contained magnetos for ignition, with dual magnetos and spark plugs per cylinder providing redundancy and increased power.
  • Pilots perform pre-flight magneto checks during run-ups, monitoring RPM drop to assess ignition system health; specific RPM drop limits and differences between mags indicate normal operation.
  • Anomalies during mag checks, such as excessive RPM drop, rough running, an engine quitting, or no RPM drop, signal potential issues like fouled spark plugs, ignition failure, or a faulty P-lead, some of which may render the aircraft unairworthy.
  • Magneto checks can also be performed airborne, and modern engine monitors (EGT/CHT) can help pilots precisely identify which cylinder and spark plug are experiencing issues.
See a mistake? Contact us.

A typical aircraft spark-ignition engine isn’t at all like the one powering the vehicle your drove to the airport. Unless, maybe, you drove a vintage tractor or motorcycle. There are so many differences, listing them here would take up lots of space, and we really only want to focus on what pilots can do and learn about their magnetos from the cockpit.

As we should know from ground school, the magnetos use energy from the operating engine to create electricity. By rotating an armature near a magnet and then sending the resulting energy into a secondary coil, high-voltage electricity is created. The mags, in turn, are connected by a wiring harness to the spark plugs, usually two of which are in each cylinder.

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