What is the maximum operational altitude for the C-5 APU?

The maximum operational altitude for the C-5 Auxiliary Power Unit (APU) is indeed 30,000 feet. This altitude limit is crucial because it defines the operational effectiveness of the APU in providing necessary hydraulic power, electrical power, and cabin air conditioning while the aircraft is on the ground or in a low power setting in flight.

Operating at or below this altitude ensures that the APU can properly maintain its performance levels against atmospheric conditions. Above the specified altitude, the APU may experience a decrease in efficiency and reliability which can adversely affect its functions when the aircraft is not driven by its main engines.

Understanding this operational ceiling is important for maintenance personnel and flight crews to ensure that the APU is used within its optimized range for reliability and safety during various flight operations.