Which component indicates if the bleed air system operates correctly?

The pressure gauge is essential for monitoring the performance of the bleed air system because it provides real-time measurements of the air pressure within the system. This is important as the bleed air system relies on maintaining specific pressure levels to ensure proper operation and functionality. When the system is operating correctly, the pressure gauge will display values within the expected range, indicating that the necessary air is being bled from the engines or the APU (Auxiliary Power Unit) as required.

In contrast, the other components do not directly measure the operational status of the bleed air system. The temperature gauge typically monitors the temperature of various fluids or air in the aircraft, which may be related but does not indicate whether the bleed air is being effectively utilized. The valve position indicator shows whether specific valves are open or closed, but it does not provide information on air pressure, which is crucial for understanding the bleed air system's functionality. The fuel gauge’s primary purpose is to indicate the amount of fuel available, making it unrelated to the bleed air system’s operation.