Continental/Bendix ignition switches are the OEM switches in most aircraft applications. Modern airplane engines
are required by Federal Aviation Regulations to have a dual ignition system, which 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; the second magneto system supplies the current to the other set of plugs. For that
reason the ignition switch has four positions: OFF, L, R, and BOTH. With the switch in the “L” or “R” position, only
one magneto is supplying current and only one set of spark plugs in each cylinder is firing. With the switch in the
BOTH position, both magnetos are supplying current and both spark plugs are firing. One advantage of the dual
ignition system is increased safety. In case one system fails, the engine may be operated on the other until a
landing is safely made. The other advantage is more complete and even combustion of the mixture, and
consequently improved engine performance; i.e., the fuel mixture will be ignited on each side of the combustion
chamber and burn toward the center.
