Can the APU be operational while the aircraft is in flight?

The option indicating that the APU is designed for ground operations only is correct because the Auxiliary Power Unit (APU) on the C-130J is specifically engineered to provide power for onboard systems, such as electrical power and pneumatic pressure, when the aircraft is on the ground. Its primary functions include starting the main engines, heating or cooling the cabin during ground operations, and powering auxiliary systems without the need to run the main engines.

During flight, the aircraft systems are powered by the engines' generators, and the APU does not operate in that environment. Safety and operational protocols dictate that the APU is not utilized in flight, as it is not equipped or certified to supply power during airborne operations, which is why the APU's operational parameters are strictly limited to when the aircraft is stationary on the ground.