What is a magneto and why is it used in aircraft engine ignition?

• A. A magneto is a primary power source for avionics.
• B. A magneto is a self-contained ignition source that generates spark energy for the engine independently of the aircraft’s electrical system.
• C. A magneto stores energy for starting.
• D. A magneto regulates voltage on the DC bus.

Answer: (B)

A magneto is a self-contained ignition source that generates the spark needed by the engine’s spark plugs independently of the aircraft’s electrical system. It works by using engine rotation to produce a high-voltage spark at the correct time without drawing power from the battery or alternator. This reliability is crucial in aviation because ignition must continue even if the aircraft’s electrical system fails. Many engines use two magnetos to provide redundancy and consistent ignition across all cylinders, with timing advanced as engine speed increases to ensure proper ignition at every RPM.

Other options don’t fit: magnetos don’t power avionics, they don’t store energy for starting, and they don’t regulate the DC bus voltage.