What is the maximum altitude for using APU bleed air?

The maximum altitude for using APU bleed air is 25,000 feet pressure altitude. This altitude limitation is established to ensure safe operation of the aircraft’s environmental and pneumatic systems. At altitudes above this limit, the air density decreases, which can affect the efficiency and effectiveness of the APU’s bleed air functions, potentially leading to insufficient performance and reliability in providing air for engine starts, cabin pressurization, air conditioning, and other systems that depend on bleed air.

Understanding this altitude restriction is crucial for flight operations and adherence to safety protocols, as exceeding it could result in operational challenges or failure to meet system demands. The thresholds provided in the other options do not align with the technical parameters of the APU’s operational capabilities, ensuring that 25,000 feet stands as the correct maximum altitude for safe and effective APU bleed air usage.