FAA Powerplant Written Practice Test

What is the power source for a booster coil on a radial engine?

1. Magnetic field

2. Battery power

3. Generator output

4. Solar energy

The correct answer is: Battery power

The power source for a booster coil on a radial engine is battery power. Booster coils function to enhance the spark provided to the ignition system, particularly in high-compression engines. They require a reliable electrical source to generate the necessary voltage that boosts the primary ignition system. In the context of radial engines, they are typically designed to operate with a 12 or 24-volt battery system that supplies DC power. The booster coil uses this battery power to create a magnetic field and subsequently generate a high-voltage pulse for the spark plugs during the ignition phase. This process helps ensure reliable starting and consistent ignition, especially when the engine is cold or under high load conditions. Other options do not serve as suitable power sources for booster coils. A magnetic field is a consequence of current flow and cannot be a standalone power source. Generator output also relies on the system being operational and does not provide the immediate initiation needed during starting. Solar energy is not applicable in this scenario, as standard aviation engines do not utilize solar power for ignition systems.