Definition
A term displayed on en route charts to indicate that radar surveillance by ATC is required on certain airways, routes, or route segments because the navigation aid coverage is insufficient to allow conventional pilot navigation. ATC must provide radar monitoring and, where necessary, vectors to keep the aircraft on course.
Plain English
On some routes, the ground-based navigation signals don't fully cover the airway, so you can't fly it by your navigation instruments alone. Controllers have to watch you on radar and give you headings as needed. If radar isn't working, you can't use that route.
Context Anchor
Seen on instrument approach charts, route descriptions, and flight notices when a procedure or route depends on ATC radar service.
Derivation
Radar began as a shortened form of “radio detection and ranging,” meaning finding an object and its distance by radio signals. Required means it is not optional; for this procedure or route segment, radar guidance is part of how it works.
Why Pilots Care
If radar services are unavailable, the pilot cannot legally or safely use the procedure and must select an alternative.
Intuition Check
“Radar Required” does not mean your aircraft must have weather radar. It means ATC radar service is needed to guide the flight on that published segment.
Example Sentence 1
The flight planning software flagged the airway segment as Radar Required, so the pilot confirmed ATC could provide continuous radar coverage before filing.
Example Sentence 2
Because the airport lacked radar coverage that day, the pilot could not fly the Radar Required procedure and diverted to an alternate airport.