Aircraft Engine Maintenance: Magneto Timing and Check

Magneto Timing

• Never advance timing beyond specifications to reduce RPM drop on single ignition, as it is an erroneous practice.
• RPM drop on single ignition is a natural characteristic of dual ignition design and should not be overemphasized.

Magneto Check

• The purpose of the magneto check is to determine if all cylinders are firing.
• If all cylinders are not firing, the engine will run extremely rough, making it apparent that investigation is needed.
• Factors that can influence RPM drop include:
• Ambient air temperature
• Humidity
• Airport altitude
• Absence of RPM drop can be a sign that the magneto timing has been set in advance of the specified setting.
• Magneto checks should be performed by comparing the performance of individual right and left magnetos.