Maximum operating altitude of APU?

Maximum operating altitude of APU?

• A. FL350
• B. FL300
• C. FL340
• D. FL360

Answer: (A)

The APU’s maximum operating altitude is tied to its ability to deliver the necessary bleed air and electrical power as air density decreases with altitude. The APU on the Citation Longitude is certified to operate up to 35,000 feet (FL350), which means it can reliably provide the required power and bleed air up to that point. Beyond that, the air is too thin for the APU’s compressor and turbine to sustain the demanded output, risking insufficient performance or an automatic shutdown. In practice, you’d use the APU for electrical power and engine starts at or below that ceiling; above it, you’d rely on other power sources.

The APU’s maximum operating altitude is tied to its ability to deliver the necessary bleed air and electrical power as air density decreases with altitude. The APU on the Citation Longitude is certified to operate up to 35,000 feet (FL350), which means it can reliably provide the required power and bleed air up to that point. Beyond that, the air is too thin for the APU’s compressor and turbine to sustain the demanded output, risking insufficient performance or an automatic shutdown. In practice, you’d use the APU for electrical power and engine starts at or below that ceiling; above it, you’d rely on other power sources.