Final answer:
The PIC will not navigate using a TACAN unless valid Radio frequency and course information are available, as these are crucial for the system's navigation functions.
Step-by-step explanation:
The Pilot in Command (PIC) will not navigate using a TACAN (Tactical Air Navigation system) unless valid Radio frequency and course information are available. TACAN is a military navigation system that provides users with bearing and distance (slant range) to a station. It is essential for the proper functioning of TACAN that both the selected radio frequency to communicate with the TACAN station and the required course or bearing to or from the station are known and valid. Without these inputs, accurate navigation using TACAN would not be possible.