A magneto is a self-contained electrical generator that uses magnets to produce a high voltage current that fires the engine spark plugs. Because of their simple design, magnetos are compact, and because they require no external electrical source to operate, they are reliable.
An aircraft magneto is comprised of a rotating magnet in close proximity to a high-output coil. As the magnet spins, it generates electricity until it achieves a spike of 20,000 to 30,000 volts. When this voltage spike is achieved, a distributor carries the amplified current to the spark plug, which ignites the fuel-air mixture to fire the pistons.
Aircraft piston engines are designed with two independent ignition systems—that is to say, two spark plugs per cylinder. Likewise, there are two magnetos, left and right. The left aircraft magneto fires one plug per cylinder, while the right aircraft magneto fires the other. This redundant system ensures that the ignition will keep sparking even if one magneto fails.
There are various types and brands of aircraft magnetos and choosing the right one for your aircraft application is important. The predominant aircraft magneto types are Slick Magnetos, Bendix dual magnetos, and Bendix single magnetos.
Currently these magnetos are manufactured by Champion Aerospace. The Slick Magneto line was acquired by Champion in 1990s. Slick Magnetos offer a smaller and lighter design compared to other aircraft magnetos. The light weight of the part allows for easier installation of a Slick Magneto. The noise suppression of the magneto is also a feature that allows for the elimination of magneto filters on Slick Magnetos.
Parts for Slick magnetos are engineered for balanced wear which allows for predictable wear on the part and time for servicing. Another benefit of Slick Magnetos is the ease to keep up maintenance due to new parts used for servicing. All repair work for a Slick Magneto is to be completed in compliance with Champion manual L1363.
A dual magneto is an arrangement in which the left aircraft magneto and right aircraft magneto are contained in a single housing and operated by a single magnet rotor and engine drive.
Due to both magnetos being together there is significant reduction in weight and space taken up by a dual magneto as compared to single magnetos. Moreover, the single-housing design allows for more regular maintenance of the ignition system.
Dual magnetos were produced by Teledyne Continental Motors until October of 2010, when the line was ended. There are two series of dual magnetos available, D2000 and D3000, which differ mainly in the design of the housing.
A Bendix single magneto, commonly referred to as a “Bendix Mag”, is a specific type of aircraft magneto manufactured by Teledyne Continental Motors. Bendix single magnetos have been in continuous production by TCM since 1947. They are known for their light weight, compact design, reliability, and high output. There are multiple models of Bendix magnetos for different types of aircraft applications.
The S-20 series Bendix magneto can be impulse coupled or direct drive. This series will have a feed through capacitor that filters out radio noise from the magneto. The “short cover” Bendix magneto, which is easily distinguished by the rear contact cover, is a variation of this series. The S-200 series Bendix magneto uses an ignition vibrator along with a retard breaker assembly to start the engine. The last series is the S-1200. These Bendix magnetos can be impulse coupled or use retard breaker contact assembly. This Bendix Magneto series is able to reach higher voltages to allow for higher altitude of flight.
Having trouble with your aircraft magneto? View our Aircraft Magneto Troubleshooting Guides!