Which of the following statements about the magneto check is true?

The correct answer is that a drop must not exceed 50 RPM between both magnetos. This standard is crucial because it ensures that both magnetos are functioning effectively, which is essential for the reliability and efficiency of the engine's ignition system. The operational limits for a magneto check are designed to identify any irregularities in either magneto performance. If the RPM drop exceeds 50 between the two, it could indicate a malfunction or a significant difference in performance that might affect engine reliability.

Since the magneto check is part of routine engine maintenance, adherence to this limit is critical for flight safety. Consequently, maintaining both magnetos within the specified RPM drop ensures that the aircraft's ignition system is in optimal condition, reducing the risk of engine failure during operation.