What is the main purpose of the APU pneumatic energy?

The main purpose of the Auxiliary Power Unit (APU) pneumatic energy is to assist in engine starting and anti-icing systems. During the start of an engine, the APU provides compressed air needed to spin the engine's starter and help with ignition. Additionally, the APU supplies pneumatic energy that can be used for anti-icing systems—this is crucial, especially in cold weather operations, as it helps prevent ice formation on critical components of the aircraft, ensuring reliable performance and safety.

This function is critical because it allows the aircraft to operate effectively both on the ground and during various phases of flight, especially in challenging weather conditions. The APU plays a vital role in preparing the aircraft for takeoff and maintaining operational readiness by ensuring that all systems are functioning correctly. Other options, while related to aircraft systems, do not directly pertain to the primary functions of APU pneumatic energy in this context.