Subchapter 9.1 – Communication Failure Under IFR

Actions immediately upon discovery of communication failure:

Squawk 7600 on the transponder (if time permits, acknowledge receipt of last clearance before squawking, or squawk immediately if you have no two-way comms).
Attempt to restore communications. Check frequency volume, squelch, and headset connections. Try alternate frequencies (approach, departure, or 121.5 MHz).
Maintain the last assigned altitude unless leaving that altitude would result in a collision. If you were cleared to climb or descend, continue that movement and level off at the last assigned altitude.
Follow the last assigned route. If you were on vectors, determine the last assigned heading and fly it. If on a published route (SID, approach), continue as filed.
If you cannot restore comms, expect no further ATC instructions. Navigate to your destination or the nearest suitable aerodrome and plan a descent and landing.