When do all of the NAV lights turn on?

• A. When the battery switches are turned on
• B. When the engine starts
• C. When the APU is running
• D. When the GPU is connected

Answer: (A)

The lights that help other pilots see your aircraft at night are powered by the aircraft’s electrical system. On this airplane, turning the battery switches to ON energizes the battery bus that feeds the navigation light circuits, so all the NAV lights come on as soon as those switches are on. Engine start isn’t the trigger by itself, and while an APU or external power can supply electrical power, the reliable and intended way to establish NAV lights is to switch the battery switches ON. This setup ensures the lights are ready and powered before or independent of engine or APU operations.