What is the maximum allowable RPM drop for the magnetos?

The maximum allowable RPM drop for the magnetos is typically set at 175 RPM for the PA-28A series. This specification ensures that both magnetos are functioning properly and are providing adequate spark to the engine for reliable performance. During a magneto check, a drop exceeding this limit may indicate an issue with the ignition system, such as a faulty magneto or problem with the spark plugs. By adhering to this RPM drop standard, pilots can confirm the integrity and reliability of the ignition system before flight, contributing to overall safety and operational effectiveness. It's crucial for pilots to understand this benchmark, as it plays a significant role in pre-flight checks and ensures that the aircraft engine will perform as expected during operation.