FAA Powerplant Written Practice Test

A common indicator of a malfunctioning magneto is irregular engine speeds. This is because the magneto is responsible for generating the electrical current needed to create the spark for combustion in the engine. If the magneto is not functioning properly, it can lead to inconsistent spark timing or strength, which results in fluctuating cylinder pressures and uneven power delivery during operation. This irregularity manifests as changes in engine RPM or overall performance issues, making it an evident sign of magneto malfunction.

The other indicators mentioned, while they may seem relevant, do not specifically point to magneto issues. Increased fuel consumption could result from various factors, such as carburetion problems or engine tuning, rather than solely because of a magneto fault. Frequent ignition failure might suggest issues within the ignition system but does not directly reflect the inconsistent performance indicative of magneto problems. Lastly, consistent engine performance would contradict the very premise of magneto malfunction, as a properly functioning magneto should contribute to stable operation.