Those of us flying aircraft with reciprocating engines should be performing what is commonly referred to as a mag check, or magneto check, prior to every flight. During the engine run-up, we turn the ignition key to the Left position to disengage or ground the right magneto, noting the rpm change, before turning the key back to Both. We then repeat this process by turning the key to Right to ground the left magneto. 288
The Other Grounding
Those of us flying aircraft with reciprocating engines should be performing what is commonly referred to as a mag check, or magneto check, prior to every flight. During the engine run-up, we turn the ignition key to the Left position to disengage or ground the right magneto, noting the rpm change, before turning the key back to Both. We then repeat this process by turning the key to Right to ground the left magneto. In addition to noting the rpm drop, if any, we also should be examining other instrument indications-fuel flow, if so equipped-and especially, the EGT values presented on a multi-probe engine monitor if one is installed.
Key Takeaways:
- Pre-flight magneto checks are essential for reciprocating engines to confirm proper operation on each magneto, identifying issues like spark plug fouling (excessive RPM drop) or incorrect timing.
- A "hot magneto" (no RPM change when selected) indicates a critical failure in the grounding system, posing a significant safety risk by preventing reliable engine shutdown and increasing the chance of an unintended engine start.
- Performing a magneto grounding check at engine shutdown is crucial to ensure both magnetos are fully grounded, mitigating the hazard of accidental engine starts when the propeller is moved, even after mixture cutoff.
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