McCulloch 40 hp

 

Aircraft Spark Plug, metal enclosed

typically results in an RPM that is about 75 RPM lower than a dual system. The two systems are typically controlled by an ignition switch in the cockpit of the airplane.

This switch arrangement permits both systems to be checked before 

taking off to ensure that both systems are working properly. During normal operation both systems are operating which provides the aircraft with the most safe and efficient operation.