Which statement best describes the APU during the start process?

The statement indicating that the APU start process is completely automatic once initiated is indeed accurate. During the APU start sequence, the aircraft systems manage various functions without the need for continuous pilot intervention. This automation encompasses several steps, such as fuel pump activation, ignition, and monitoring of the start status.

When the APU start is initiated by the pilot, the aircraft's onboard systems handle the ignition sequence and the necessary fuel management. The pilot's role primarily involves the initial selection to start the APU, after which the automation takes over and allows the APU to start without further manual control. This feature not only simplifies the process for the pilot but also enhances safety and operational efficiency.

In contrast, the other statements suggest actions or requirements that are not consistent with the characteristics of the APU start process. For example, ignition occurring prior to the FLAP OPEN indication implies a sequence that doesn't align with the automatic processes in place. The notion that the pilot must manually turn on the APU fuel pump before starting overlooks the automated system’s capability to do this, and stating that the APU can only be started with external power disregards its independence as a self-contained unit that can start using internal fuel sources when required.