Regardless of the selected flow rate, the system delivers high flow when: - in single-pack operation, or - when the APU is supplying bleed air.

Regardless of the selected flow rate, the system delivers high flow when: - in single-pack operation, or - when the APU is supplying bleed air.

• A. In double-pack operation
• B. Only when packs are off
• C. When the air conditioning system is off
• D. In single-pack operation, or when the APU is supplying bleed air.

Answer: (D)

High flow is available when the cabin is being supplied by a single conditioning pack or when bleed air is coming from the APU. With only one pack active, there’s no second pack to share the airflow, so the system can open the flow path to its maximum to meet demand. If the source is the APU bleed, that bleed air provides a strong, steady supply that allows the system to deliver high mass flow to the cabin regardless of the selected pack flow setting. In contrast, when two packs are operating from engine bleed, the flow is managed to balance both packs, which keeps the delivered flow below the high setting.

High flow is available when the cabin is being supplied by a single conditioning pack or when bleed air is coming from the APU. With only one pack active, there’s no second pack to share the airflow, so the system can open the flow path to its maximum to meet demand. If the source is the APU bleed, that bleed air provides a strong, steady supply that allows the system to deliver high mass flow to the cabin regardless of the selected pack flow setting. In contrast, when two packs are operating from engine bleed, the flow is managed to balance both packs, which keeps the delivered flow below the high setting.