What is a magneto?

• A. A self-contained, engine-driven unit that supplies electrical current to the spark plugs; completely independent of the airplane's electrical system. Normally there are two magnetos per engine.
• B. A device used to measure heading on the cockpit compass.
• C. A type of fuel pump.
• D. A sensor for airspeed measurement.

Answer: (A)

A magneto is a self-contained, engine-driven unit that supplies electrical current to the spark plugs, completely independent of the airplane’s electrical system. Because it’s driven by the engine, it will continue to provide ignition even if the aircraft’s battery or alternator fails. Most piston engines use two magnetos for redundancy and reliability, so each magneto can fire the spark plugs across the cylinders, helping ensure consistent ignition. The other options describe a heading-measuring device, a fuel pump, and an airspeed sensor, which are not related to the ignition system.