Where does an APU derive its fuel supply from?

An auxiliary power unit (APU) derives its fuel supply from the aircraft's main fuel supply. This is because the APU is designed to enhance the efficiency and mechanics of the aircraft while on the ground, providing power for functions such as electrical generation, environmental control, and pneumatic pressure for starting the main engines. By drawing fuel from the main fuel tanks, the APU utilizes the existing fuel system already in place, allowing for a more streamlined approach to fuel management aboard the aircraft.

This system ensures that the APU operates efficiently without needing a separate fuel tank, which would add unnecessary weight and complexity to the design of the aircraft. Utilizing the aircraft's main fuel supply also helps in maintaining fuel balance and simplifies logistics, as the same fuel is used for the main engines and the APU.