When making a magneto check on an engine equipped with a constant-speed propeller, should the propeller control be in the low-pitch or high-pitch position?

When making a magneto check on an engine equipped with a constant-speed propeller, should the propeller control be in the low-pitch or high-pitch position?

• A. High-pitch, high RPM position.
• B. High-pitch, low RPM position.
• C. Low-pitch, low RPM position.
• D. Low-pitch, high RPM position.

Answer: (D)

When checking magnetos on an engine with a constant-speed prop, you want the engine turning fast and the prop causing as little load as possible. Setting the propeller to low-pitch (fine) lets the engine reach a high RPM under the existing throttle setting. At high RPM, the magnetos produce a stronger, more reliable spark, and the magneto drop test becomes meaningful because you’re observing the system under the speed range where ignition performance is most critical. If the prop were in high-pitch, the engine would be heavily loaded and wouldn’t reach the required RPM, making the check less reliable and potentially masking faults. So, the proper setup is low-pitch, high RPM.

When checking magnetos on an engine with a constant-speed prop, you want the engine turning fast and the prop causing as little load as possible. Setting the propeller to low-pitch (fine) lets the engine reach a high RPM under the existing throttle setting. At high RPM, the magnetos produce a stronger, more reliable spark, and the magneto drop test becomes meaningful because you’re observing the system under the speed range where ignition performance is most critical. If the prop were in high-pitch, the engine would be heavily loaded and wouldn’t reach the required RPM, making the check less reliable and potentially masking faults. So, the proper setup is low-pitch, high RPM.