What is the primary purpose of an ammeter in an aircraft electrical system?

• A. To monitor fuel consumption of electrical accessories.
• B. To measure voltage across the main bus.
• C. To indicate the total current flow to or from the electrical system, helping monitor charging and discharging of the battery and generator output.
• D. To regulate frequency of AC power.

Answer: (C)

An ammeter’s job is to show how much current is flowing into or out of the aircraft’s electrical system. This lets you see whether the battery is being charged by the generator or being discharged to power the loads. It provides a quick overall picture of the system’s current balance, so you can detect if the generator isn’t delivering enough current or if the battery is supplying power due to an overload or generator fault. It reads positive when the system is charging and negative when the battery is supplying power. It does not measure fuel use, it does not indicate voltage across the main bus (that’s the voltmeter’s job), and it does not regulate AC power frequency (that’s managed by the generator and its control system).