How is the priority between engine and APU bleed air managed?

The management of priority between engine and APU (Auxiliary Power Unit) bleed air is handled automatically by the AMSAC (Air Management System Automation Control). This system is designed to optimize the use of bleed air for cabin pressurization, air conditioning, and other pneumatic needs of the aircraft. By using automatic controls, the AMSAC can adjust the priority based on demand, temperature, and operational requirements, ensuring an efficient and reliable supply of bleed air.

This automation reduces pilot workload and enhances safety, as the system can make rapid adjustments in real-time to meet the needs of the aircraft without the need for manual intervention. In contrast, other options involving manual management or hydraulic systems do not provide the same level of efficiency and responsiveness, which is crucial in high-demand flight situations. Hence, relying on the AMSAC for bleed air priority management ensures both optimal efficiency and operational safety onboard the aircraft.