How long can the APU run continuously without requiring a shutdown?

The APU (Auxiliary Power Unit) on the C-130J can run continuously for several hours without needing a shutdown. This capability is vital for providing electrical power and pneumatic pressure when the main engines are not operating, especially during ground operations or pre-flight preparations. Operating the APU for this duration allows ground crews to perform necessary tasks, such as running onboard systems, without taxing the aircraft’s main engines or consuming fuel unnecessarily.

While considerations for maintenance and operational guidelines give specific limits based on factors like temperature and load conditions, the APU is designed not to be limited to just a few minutes. It also is not intended for indefinite operation, as prolonged activity can lead to wear and overheating. Additionally, its use is not limited to during flight—rather, it serves critical functions during ground operations as well.