What will happen if the reverse current cutout relay contacts fail to open when the generator output drops below battery potential?

When the reverse current cutout relay contacts fail to open, it allows current to flow in the opposite direction through the shunt field of the generator. This situation occurs when the generator output drops below the battery's potential, essentially creating a condition where the battery can start to discharge through the generator rather than charging it.

In a normal operating scenario, the reverse current cutout relay is designed to prevent such reverse flow to protect the generator. If the relay contacts do not open as expected, the battery can supply current to the generator's shunt field, causing the generator to operate inefficiently or potentially damage the electrical components. The result is that the current runs contrary to the normal operating direction through the shunt field, leading to improper generator functionality and possible system failures.

Understanding this mechanism is crucial for ensuring that the aircraft's electrical system remains functional and safe.