APU bleed air can supply one pack and assist in engine start up to which altitude?

APU bleed air can supply one pack and assist in engine start up to which altitude?

• A. 15,000 ft
• B. 10,000 ft
• C. 20,000 ft
• D. 25,000 ft

Answer: (C)

Bleed air sources have a limited capability, and the APU bleed is sized to handle only a certain amount of airflow. In the A320, the APU bleed can feed air to one environmental control pack and can also assist engine starting, but only up to a certain altitude where the mass flow and pressure it can provide are still adequate. That limit is about 20,000 feet. At higher altitude, the APU bleed cannot reliably supply enough airflow to both feed a pack and assist engine starts, so you’d rely on other sources (engine bleeds or external air) instead. So the correct altitude is 20,000 feet.

Bleed air sources have a limited capability, and the APU bleed is sized to handle only a certain amount of airflow. In the A320, the APU bleed can feed air to one environmental control pack and can also assist engine starting, but only up to a certain altitude where the mass flow and pressure it can provide are still adequate. That limit is about 20,000 feet. At higher altitude, the APU bleed cannot reliably supply enough airflow to both feed a pack and assist engine starts, so you’d rely on other sources (engine bleeds or external air) instead. So the correct altitude is 20,000 feet.