At what maximum altitude can the C-130J APU operate effectively?

The C-130J APU (Auxiliary Power Unit) is designed to provide power for various systems during ground operations and can also assist with engine start. Its effective operational ceiling is crucial for ensuring that it delivers adequate performance in supporting the aircraft's systems when needed.

The correct altitude for the C-130J APU's effective operation is 25,000 feet. This capability allows the aircraft to maintain functionality in high-altitude environments, which is essential for missions that may take place in mountainous regions or other elevated areas. Operating above this altitude can lead to decreased efficiency of the APU, compromising its ability to supply power and possibly affecting onboard systems.

Understanding this aspect of the APU is vital for crew members as it ensures they can utilize the APU effectively, providing the necessary power without exceeding operational limits that could lead to equipment failure.