What should you do with the anti-skid fail annunciator illuminated?

When the anti-skid fail annunciator is illuminated, it signifies that the anti-skid system is not functioning correctly. This system is crucial for maintaining optimal braking performance and preventing wheel lock-up during braking, particularly on slippery surfaces.

Turning the switch to the off position after such an indication is the appropriate action because it allows the pilot to disable a potentially faulty system that could adversely affect aircraft handling and braking performance. By doing so, the pilot mitigates risks associated with unexpected braking behavior, thus promoting a safer operational environment until the issue is addressed further.

Reviewing the other options provides further insight into the rationale behind the correct choice. Leaving the switch as it is could allow the malfunctioning system to remain active, potentially leading to unsafe braking conditions. Adjusting the switch to auto would not be advisable either, as it could still lead to the same issues without resolving the malfunction indicated by the light. Notifying the crew is essential, but taking direct action to mitigate the problem actively is critical in this situation. Hence, turning it to off is the most responsible course of action.