What is the lower bound of the APU continuous operation temperature?

What is the lower bound of the APU continuous operation temperature?

• A. -60°C
• B. -54°C
• C. -52°C
• D. -50°C

Answer: (B)

APU continuous operation temperature defines the minimum ambient temperature at which the APU is approved to run without interruption. This limit is set to ensure reliable start and steady operation by keeping fluids and components within their safe, tested ranges. At very low temperatures, lubricant viscosity increases and fuel and hydraulic properties can degrade, making starting and continuous operation unreliable. The established lower bound for the APU is minus 54 degrees Celsius, so operating continuously below that temperature isn’t approved. The other temperatures are either warmer limits or not the certified continuous-operation lower bound.

APU continuous operation temperature defines the minimum ambient temperature at which the APU is approved to run without interruption. This limit is set to ensure reliable start and steady operation by keeping fluids and components within their safe, tested ranges. At very low temperatures, lubricant viscosity increases and fuel and hydraulic properties can degrade, making starting and continuous operation unreliable. The established lower bound for the APU is minus 54 degrees Celsius, so operating continuously below that temperature isn’t approved. The other temperatures are either warmer limits or not the certified continuous-operation lower bound.