What altitude is allowed for continuous operation electrical generation use by the APU?

What altitude is allowed for continuous operation electrical generation use by the APU?

• A. 28,000 ft
• B. 33,000 ft
• C. 35,000 ft
• D. 38,000 ft

Answer: (B)

Continuous electrical generation from the APU is limited by cooling and component limits. As the aircraft climbs, the air available to carry away heat becomes thinner, so the APU must stay within safe temperatures if it’s to run for an extended period. There is a ceiling altitude where the cooling and other margins allow continuous operation; above that, the APU can’t be kept running indefinitely without risking overheating or other issues. That’s why the maximum altitude at which you can use the APU to generate electrical power continuously is the value chosen in the question. If you need electrical power above that point, you would have to rely on other sources or restrict the APU’s operation to shorter durations.

Continuous electrical generation from the APU is limited by cooling and component limits. As the aircraft climbs, the air available to carry away heat becomes thinner, so the APU must stay within safe temperatures if it’s to run for an extended period. There is a ceiling altitude where the cooling and other margins allow continuous operation; above that, the APU can’t be kept running indefinitely without risking overheating or other issues. That’s why the maximum altitude at which you can use the APU to generate electrical power continuously is the value chosen in the question. If you need electrical power above that point, you would have to rely on other sources or restrict the APU’s operation to shorter durations.