What should a controller do if a pilot reports loss of all low frequency navigational receiving capability?

When a pilot reports a loss of all low frequency navigational receiving capability, the most appropriate action for the controller is to notify other controllers and provide the required assistance. This response is essential for ensuring the safety of the flight, as the loss of navigational capability can significantly affect the pilot's situational awareness and ability to navigate safely.

By notifying other controllers, the information can be disseminated throughout the air traffic control environment. This enables other controllers to be aware of the aircraft's situation, adjusting traffic flow and providing additional support as necessary. Furthermore, prompt assistance can include guiding the pilot through alternatives, such as vectors or other navigational aids that may still be functional.

In contrast, issuing a standard holding pattern or directing the pilot to land immediately may not address the immediate needs of the aircraft, especially if the pilot can maintain control and navigate safely using other methods. Instructing the pilot to switch to backup systems may also be useful, but it does not encompass the broader responsibility of ensuring that all necessary coordination and support are provided by the air traffic control team. Therefore, the most comprehensive and effective response is to notify other controllers and deliver the required assistance.