If a TACAN fails during radar vectors to an ILS, what must pilots do according to standard procedures?

When a TACAN (Tactical Air Navigation) system fails during radar vectors to an Instrument Landing System (ILS), standard procedures require pilots to obtain alternate missed approach instructions. This is because TACAN provides critical navigational information that pilots rely on for continued safe flight and approach execution. If this system fails, it can compromise the pilot's ability to accurately navigate, especially during the crucial phases of descent and approach.

Obtaining alternate missed approach instructions ensures that pilots have a clear understanding of what to do if they cannot land as planned due to the loss of TACAN information. It allows them to safely execute the missed approach procedure based on the latest, most relevant guidance from air traffic control (ATC), ensuring safety and compliance with standard operating protocols.

While other options might suggest continuing the approach or assuming conditions will allow visual flight rules (VFR), those may not adhere to the safety regulations and standard operating procedures that prioritize structured responses to navigational system failures.