What does the Start Bus use as its primary power source?

The Start Bus primarily operates using a battery or Ground Power Unit (GPU) as its power source. The Start Bus is typically used in aircraft to initiate the engine start process and power various systems while the aircraft is on the ground. Batteries provide a reliable source of energy when engines are not running and are essential for starting the aircraft's engines, especially in situations where the aircraft is not connected to a GPU. The GPU serves as an external source of power that can be connected to the aircraft to supply electrical power, aiding in starting the engines and powering onboard systems during ground operations.

Using batteries or a GPU ensures that the Start Bus can function effectively without relying on the aircraft's engines, making it a versatile and dependable power source in various operational scenarios.