During an APU ground start, which message indicates that the APU SOV is open?

The message indicating that the APU (Auxiliary Power Unit) SOV (Shutoff Valve) is open is "APU SOV OPEN." This message confirms that the valve, which controls fuel flow to the APU, has been successfully opened, allowing the APU to receive the necessary fuel to start its operation.

When observing this message during an APU ground start, it provides assurance to the flight crew that the system is functioning correctly and that the APU is ready to begin its start sequence. It's crucial for operational safety and efficiency, as the APU needs to be operational to supply electrical power and bleed air for engine starting and air conditioning during ground operations.

The other options convey important information but are not specifically related to the status of the APU SOV. For instance, "APU IN BITE" refers to the APU's built-in test equipment being active, which does not directly confirm the valve's status. "DOOR OPEN" typically relates to door configurations rather than fuel system components. Similarly, "APU Gauges Active" would indicate that the gauges for monitoring the APU systems are operational but do not specifically confirm the open status of the fuel shutoff valve.