If the APU generator fail light comes on during operation, what is the appropriate course of action?

When the APU generator fail light illuminates during operation, the appropriate action is to shut down the APU immediately. This is crucial because a failing generator can compromise not only the function of the APU but also the overall electrical system of the aircraft.

Immediate shutdown allows for the potential prevention of further damage to the APU or other connected systems, and it ensures safety by not relying on a failing power source. Addressing the situation promptly helps maintain operational integrity and safety.

Continuing operation could lead to further complications, and contacting maintenance or reducing engine power would not solve the issue at hand rapidly enough, potentially putting the aircraft at greater risk. Therefore, an immediate shutdown is the most prudent course of action.