What is the maximum altitude for APU bleed use?

The maximum altitude for APU bleed use is set at 15,000 feet. This limitation is in place to ensure the safe and efficient operation of the aircraft's Auxiliary Power Unit (APU). Above this altitude, the performance of the APU can be compromised due to the reduced ambient air density, which affects both combustion efficiency and the ability to provide necessary pneumatic pressure for bleed air systems.

In operation, the APU provides critical bleed air for various systems, including environmental control and engine start assistance. At altitudes lower than 15,000 feet, the APU can function effectively within its operating parameters, ensuring that all systems reliant on bleed air are provided with sufficient pressure and flow. However, exceeding the specified altitude can lead to insufficient bleed air performance, which might impact the operation of essential systems and increase the risk of overheating or failure.

Understanding these limitations is vital for pilots and operational personnel to maintain safety and performance throughout all phases of flight. This altitude limitation directly relates to the design and operational capabilities of the APU, emphasizing the need for adherence to manufacturer specifications.