What is the purpose of the battery?

• A. To power the radio
• B. It is the starter motor to turn the engine
• C. To generate electrical power for avionics
• D. To power the starter alternator

Answer: (B)

The main idea is that the battery’s job is to provide the initial electrical energy needed to start the engine by powering the starter motor. When you activate the start switch or key, the battery delivers a high current to the starter, turning the engine over until it fires. Once the engine is running, the aircraft’s electrical system is typically supplied by the alternator (generator) and this power also recharges the battery. That’s why avionics and radios are powered by the system once the engine is running, not directly by the battery as the primary source. The term about a “starter alternator” isn’t the usual arrangement; the starter is powered by the battery, and the alternator/generator then supplies ongoing electrical power and keeps the battery charged.