Which altitude corresponds to the maximum altitude for APU bleed only?

• A. 41,000 ft
• B. 10,000 ft
• C. 17,000 ft
• D. 14,000 ft

Answer: (C)

APU bleed capability has a ceiling set by the pressure the APU can deliver as altitude increases. The environmental control system and cabin pressurization require a minimum bleed-air pressure to function, so there’s a limit to how high you can rely on APU bleed alone. For the P-8A, that limit is about 17,000 ft, meaning you can support the ECS with APU bleed up to that altitude, but not above it. Among the given values, 17,000 ft is the highest altitude at which APU bleed alone can meet the system needs; higher altitudes would require engine bleed or another source.