When does a "Full Load" condition occur?

A "Full Load" condition occurs when one Auxiliary Power Unit (APU) is supplying bleed air and the AIR COND switch is in the BOTH position. This scenario exemplifies a full operational demand on the APU, as it is providing the maximum necessary airflow for cooling or pressurizing the aircraft, especially when conditions require the full capacity of the APU to maintain the desired environmental conditions within the aircraft.

In this case, having the AIR COND switch in the BOTH position indicates that the system requires air from both the left and right packs, thereby maximizing the load on the APU. The operational efficiency and capacity of the APU are critical in managing temperature, pressurization, and environmental control, making this setup essential for optimal APU performance.

Other scenarios, such as having no APU supplying bleed air, the operation of two APUs simultaneously, or relying on external power, do not fulfill the requirements for a "Full Load" condition as they either reduce the operational demand on the APU or do not engage its systems in full capacity.