What color is the AVAIL light on the APU start pushbutton when the APU is running?

What color is the AVAIL light on the APU start pushbutton when the APU is running?

• A. Green
• B. Amber
• C. Red
• D. Off

Answer: (A)

The AVAIL light on the APU start pushbutton shows whether the APU is ready to supply power or air. When the APU has started and is available to be used (i.e., it’s running or ready to run), that indicator is green. In this state you know the APU is healthy and can support electrical or pneumatic needs. If the APU isn’t available due to a fault or is not ready to operate, the light would be amber or off, and you’d rely on other indicators to assess status. So, during normal operation with the APU running, the AVAIL light being green is the expected and correct indication.

The AVAIL light on the APU start pushbutton shows whether the APU is ready to supply power or air. When the APU has started and is available to be used (i.e., it’s running or ready to run), that indicator is green. In this state you know the APU is healthy and can support electrical or pneumatic needs. If the APU isn’t available due to a fault or is not ready to operate, the light would be amber or off, and you’d rely on other indicators to assess status. So, during normal operation with the APU running, the AVAIL light being green is the expected and correct indication.