Plain English Meaning

Something has gone wrong with the radios or navigation equipment, so the pilot can no longer talk to controllers or navigate the way they were planning to. There are set rules for what to do next so the flight can still finish safely.

Full Definition

A failure or abnormal operation of onboard radios, navigation receivers, or related avionics that prevents the pilot from communicating with air traffic control or navigating by the intended means. Such malfunctions trigger specific lost-communication and lost-navigation procedures defined by regulation and by the flight's clearance, allowing the pilot to continue and complete the flight safely under known rules.

Context Anchor

Encountered during when a , navigation , , , or related electrical equipment stops working normally or gives information.