Words for: Preflight Procedures
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The switch in the cockpit that turns the engine's ignition on or off and lets the pilot test each ignition system separately.
The cockpit control, usually a key-operated rotary switch, that selects which of the airplane's magnetos are providing electrical current to the spark plugs. Typical positions are OFF, R (right magneto only), L (left magneto only), BOTH, and START. When the switch is OFF, both magnetos are grounded and cannot fire the engine.
Seen during engine start, engine run-up, shutdown, and especially during hand propping, where an incorrect switch position can make the engine start unexpectedly.
A magneto is a small engine-driven generator that produces its own high-voltage spark, named from the Greek root for 'magnet' because it works by spinning magnets past a coil. The switch is named after the device it controls.
Proper use prevents accidental engine rotation during hand propping and ensures reliable ignition once running.
Do not assume OFF is only a normal electrical off switch. On many aircraft, OFF works by grounding the magnetos; if that ground path fails, the magneto can still make spark.
During the runup, the pilot moved the magneto switch from BOTH to R, noted the rpm drop, then back to BOTH before testing L.
After the engine started, the pilot moved the magneto switch to BOTH for normal flight operation.