What is the APU continuous operation altitude?

What is the APU continuous operation altitude?

• A. 28,000 ft
• B. 33,000 ft
• C. 37,000 ft
• D. 40,000 ft

Answer: (B)

The APU continuous operation altitude is the highest altitude at which the APU can run continuously while still providing the required electrical power and bleed air. For the ERJ 175, that limit is 33,000 ft because, beyond that altitude, the APU cannot sustain the needed bleed air flow and cooling to run continuously without compromising performance or risking overheating. So 33,000 ft is the maximum altitude for continuous APU operation. At higher altitudes like 37,000 ft or 40,000 ft, continuous operation isn’t permitted, even though the APU might start or run intermittently for brief periods. The other option, 28,000 ft, is below the limit but doesn’t represent the maximum continuous capability, which is what the question asks.

The APU continuous operation altitude is the highest altitude at which the APU can run continuously while still providing the required electrical power and bleed air. For the ERJ 175, that limit is 33,000 ft because, beyond that altitude, the APU cannot sustain the needed bleed air flow and cooling to run continuously without compromising performance or risking overheating. So 33,000 ft is the maximum altitude for continuous APU operation.

At higher altitudes like 37,000 ft or 40,000 ft, continuous operation isn’t permitted, even though the APU might start or run intermittently for brief periods. The other option, 28,000 ft, is below the limit but doesn’t represent the maximum continuous capability, which is what the question asks.