Harmon Technologies, Inc.

Magneto Switch

The magneto switch is a key switch that is sort of like the ignition key of a car.  It has five positions, Off, left, right, both, and start.  Unlike a car engine, an aircraft engine has two completely independent ignition systems and two spark plugs for each cylinder.  This switch is used to start the engine and normally, the engine runs with both ignition systems working.  The switch allows one or the other system to be enabled separately.  This is used during the run-up test that is done before takeoff to make sure that both systems are operating properly.  Should a partial failure of one system cause slightly rough engine operation, that system could be disabled using this switch.  While ignition system failures are very rare, normally, the other system performs so well that nobody is aware that there even was a problem until the systems are independently tested before the next flight.

Copyright © 2004 Harmon Technologies, Inc.