Final answer:
In the event of a loss of communication while being radar vectored in IFR conditions, the pilot must follow the last known ATC instruction, adhere to the flight plan, and use standard IFR lost communication procedures to ensure safety.
Step-by-step explanation:
If a pilot is being radar vectored in IFR conditions and loses radio communications with ATC, specific action must be taken to ensure safety and compliance with regulations. The pilot should continue flying the last assigned vector until reaching the fix, route, or airway specified in the vector clearance. If no fix, route, or airway was specified, the pilot should proceed via the direct route from the point of radio failure to the fix, route, or airway last advised by ATC as the expected further clearance.
Moreover, the pilot should maintain the last assigned altitude for a specified time. If the clearance limits the time at that altitude, after that time expires, the pilot should climb or descend to the altitude specified in the filed flight plan for that segment of the flight. If ATC has previously advised an expect further clearance (EFC) time, the pilot should begin descent so as to arrive at the approach gate at the EFC time.
When the pilot reaches the vicinity of the destination airport and it is safe to do so, they should commence the approach based on the filed alternate flight plan or, if no alternate was filed, as per the standard lost communication procedures outlined in the aviation regulations. The key is to continue to comply with the last known instruction from ATC and to follow standard IFR lost communication procedures. This will ensure the action taken is in the best interest of safety.