Which control is used to shut down the APU?

The APU shutdown switch is specifically designed for the purpose of shutting down the Auxiliary Power Unit (APU). This switch provides the necessary command to stop the operation of the APU safely. When engaged, it initiates a controlled shutdown process, allowing the system to follow a predetermined sequence to turn off the APU, ensuring that it doesn't stop abruptly, which could potentially cause damage or unsafe conditions.

Other controls do serve important functions but are not specifically used for shutting down the APU. For instance, the APU power switch is primarily for powering the APU on or off but doesn't directly manage the shutdown process. The APU status indicator provides information about the operational status of the APU, while the emergency stop button is meant for immediate shutdown during emergency situations, which is different from the standard shutdown procedure facilitated by the shutdown switch. Understanding the roles of these various controls helps maintain proper operation and safety during APU management.