What is the fuel source for the APU?

The correct fuel source for the APU (Auxiliary Power Unit) on the C-130J is gravity fed from the No. 2 main tank. This fuel supply method is efficient and ensures that the APU receives an adequate amount of fuel for operation without the need for complex pumping systems.

Main tanks, specifically the No. 2 tank in this case, are designed to supply fuel to various components of the aircraft, including the APU. The gravity feed system is advantageous because it simplifies the design and reduces the potential points of failure compared to a system that relies on pumps, thus enhancing reliability during operation.

Other options involve various fuel tank configurations that either do not supply fuel to the APU or refer to auxiliary tank systems which are not designated for this specific function. Understanding the APU's fuel source is essential for ensuring proper operations and maintenance on the C-130J, and knowing that it draws from the No. 2 main tank helps streamline fuel management during missions.