On which bus is external power distributed?

The correct answer is the battery bus. In the T-6 aircraft, external power is connected to the battery bus to supply electrical power to all essential systems when the aircraft is on the ground and not powered by the engines. This configuration allows for the charging of the battery as well as powering of avionics and other electrical systems without requiring the engines to be running.

During ground operations, especially for pre-flight checks or when the engines are not operating, utilizing battery power ensures that the necessary equipment can be functional for pilot training and maintenance. The battery bus serves as the initial point where external power is received before being distributed further to other systems as needed.

Other buses like the generator bus, main bus, and accessory bus perform different functions in the aircraft's electrical system, with the generator bus primarily being powered by the aircraft's onboard generators once they are running, rather than connecting directly to external power sources.