What is the minimum starting temperature for the APU?

The minimum starting temperature for the Auxiliary Power Unit (APU) is critical for understanding its operational limits. The correct answer indicates that the APU can reliably start at temperatures as low as -54 degrees Celsius. This temperature threshold is important because it reflects the APU’s capability to function in extremely cold environments, which is essential for maintaining operations in harsh weather conditions often faced in aviation.

In contrast, the other temperatures listed do not represent the limits of operation for the APU. While some may be permissible for other equipment or scenarios, -54 degrees Celsius is the standard recognized by manufacturers and engineering specifications, ensuring optimal functionality and safety during operations in cold climates. Failing to operate within these defined limits can lead to issues such as inadequate power generation or mechanical failure, which is why knowing the precise minimum temperature is vital for pilots and maintenance personnel.