What is the procedure for handling an aircraft experiencing a complete radio failure in controlled airspace?

The procedure for handling an aircraft experiencing a complete radio failure in controlled airspace is based on a set of established rules designed to ensure the aircraft can continue its flight safely and predictably. These rules are outlined in aviation regulations and are commonly referred to as 'lost communication' procedures. The pilot's first action should be to attempt to troubleshoot the radio failure, such as checking volume settings, frequencies, and circuit breakers. If communication cannot be re-established, the pilot should then squawk 7600 on the transponder. Squawking 7600 is a discrete transponder code that alerts air traffic control (ATC) that the aircraft has lost radio communication. The pilot should then maintain the highest of the following: the altitude assigned in the last ATC clearance, the minimum altitude for IFR operations, or the altitude ATC has advised to expect. The pilot should also fly the route assigned in the last ATC clearance. However, if being radar vectored, the pilot should proceed by the most direct route from the point of radio failure to the fix, route, or airway specified in the vector clearance. If no route has been assigned, the pilot should proceed via the route that ATC has advised to expect in a further clearance. The pilot should then proceed to the clearance limit specified in their ATC clearance. If the clearance limit is a fix from which an approach begins, the pilot should commence descent or descent and approach as close as possible to the expect-further-clearance time if one has been received, or if one has not been received, as close as possible to the estimated time of arrival (ETA) as calculated from the last known position. If the clearance limit is not a fix from which an approach begins, the pilot should, upon arriving over the clearance limit, proceed outbound for a published or assigned holding fix. The aircraft should hold until the expect-further-clearance time, or if no expect-further-clearance time has been issued, until the ETA. The pilot should then commence descent and approach. If operating under visual meteorological conditions (VMC), the pilot should continue the flight under VMC and land as soon as practicable. These procedures allow ATC to anticipate the aircraft's actions and maintain separation from other traffic. Therefore, following these established procedures is crucial for ensuring the safe continuation of flight in the event of a complete radio failure.