FAA Powerplant Written Practice Test

In a dual magneto ignition system, what component is shared by both ignition systems?

1. Ignition coil

2. Rotating magnet

3. Power switch

4. Distributor cap

The correct answer is: Rotating magnet

In a dual magneto ignition system, the rotating magnet is the component that is shared by both ignition systems. In this setup, there are typically two magnetos which generate high voltage for spark ignition. The rotating magnet functions as the source of magnetic flux, and as it rotates, it induces an electrical current in the coils within each magneto. This inductive method ensures that when the magnet moves past the coils, it creates an alternating current that is transformed into the high voltage needed to create a spark at the spark plugs. This design is crucial because it provides redundancy; if one magneto fails, the other can still provide sufficient ignition for engine operation, enhancing reliability and safety in aircraft engines. The shared rotating magnet is essential for synchronizing the timing of the ignition events for both systems, facilitating their simultaneous operation to ensure proper combustion. Other components such as the ignition coil, power switch, and distributor cap are typically dedicated to individual ignitions or specific control functions within the engine's ignition system. They do not have the dual functionality offered by the shared rotating magnet that directly contributes to the fundamental working of both ignition sources.