When is it mandatory for a pilot to have a radio during flight?

Having a radio is mandatory for a pilot when flying in controlled airspace. This requirement ensures effective communication with Air Traffic Control (ATC), which is critical for managing traffic and maintaining safety in airspace where there are higher densities of aircraft. Controlled airspace typically encompasses areas around major airports and flight corridors where ATC services are provided.

In this environment, pilots must receive clearances, advisories, and instructions from ATC to coordinate their movements with those of other aircraft. This helps prevent collisions and facilitates efficient air traffic management. Therefore, flying without a functioning radio in controlled airspace would not only violate regulations but could also pose significant safety risks.

In contrast, while flying in uncontrolled airspace does not require a pilot to have a radio, communication with other pilots can enhance safety but is not mandatory. Similarly, flying at night does not necessitate having a radio, nor does conducting a go-around, although having one might be beneficial in these situations for communication purposes.