The function of the aviation piston engine ignition system is to provide an electrical spark to ignite the fuel/air mixture in the engine cylinders. The ignition system of the engine is a separate system and is not part of the airplane’s overall electrical system. The magneto type ignition system is used on most reciprocating aircraft engines. Magnetos are engine-driven self-contained units that supply electrical current without using an external source of current. Magnetos are frequently not maintained to requirements specified in L1363 Manual- 4300/6300 Series Magneto Maintenance and Overhaul Manual, probably because they’re so reliable and all engines have a redundant magneto. Magnetos need regular maintenance, and the consequences of neglect can be devastating.
Modern airplane engines are required by to have a dual ignition system – that is, two separate magnetos to supply the electric current to the two spark plugs contained in each cylinder. One magneto system supplies the current to one set of plugs, while the second magneto system supplies the current to the other set of plugs. The airplane’s double ignition system provides better performance because of more efficient combustion and a higher level of safety through redundancy.