Definition
Geographic points along an airway or route that are identified by reference to ground-based radio navigation aids, such as VORs, NDBs, or DME, and used to define position, route segments, and altitude requirements.
Plain English
Specific spots in the sky that pilots can identify using signals from ground radio stations. They mark known points along a route.
Context Anchor
Seen on instrument en route charts and in minimum en route altitude discussions, especially when a route segment is described from one fix to the next.
Derivation
Fix' comes from the idea of 'fixing' your position — pinning it down to a known spot. 'Radio' indicates that the position is established using radio navigation signals rather than visual landmarks or GPS.
Why Pilots Care
Radio fixes mark the points between which minimum altitudes are calculated to guarantee reliable navigation signal coverage and obstacle clearance.
Intuition Check
A fix is not something being repaired. In navigation, a fix means a known position; radio fixes are known positions identified by radio signals.
Example Sentence 1
The minimum en route altitude applies to the segment between two radio fixes along the airway.
Example Sentence 2
MEAs are established between consecutive radio fixes to maintain continuous reception of navigation signals.