What are signs of fouled spark plugs?

Fouled spark plugs can significantly impact engine performance, and recognizing the signs is crucial for maintenance and safety in aviation. The correct answer focuses on two specific symptoms: a rough idle of the engine and a high RPM drop during a magneto check.

When spark plugs become fouled, they can be coated with oil, carbon, or other contaminants, which hinders their ability to produce a strong spark. This can lead to an uneven combustion process, resulting in a rough engine idle because the fuel-air mixture is not igniting efficiently. During a magneto check, you perform this test to assess the performance of the ignition system by momentarily cutting off one magneto at a time. A high RPM drop while doing this suggests that one magneto is not functioning adequately due to the fouled spark plugs, leading to a more significant drop in RPM compared to when both magnetos are operational.

The other options may describe notable engine performance issues, but they do not directly correlate with the typical symptoms of fouled spark plugs. For example, signs like high fuel flow and engine misfires may indicate other issues such as fuel system problems or ignition failures. Smoky exhaust usually points to burning oil rather than fouled plugs, and low oil pressure is a serious