Definition
The primary navigation receiver in an aircraft's avionics stack, used to receive signals from ground-based navigation aids such as VORs and localizers, and to display course guidance to the pilot. In aircraft equipped with two navigation radios, Navigation Radio #1 is the designated main unit, while Navigation Radio #2 serves as a secondary or cross-check source. On installations with a standby battery, Navigation Radio #1 is typically among the essential items kept powered if the main electrical system fails.
Plain English
The aircraft's main radio for picking up signals from navigation stations on the ground and showing the pilot which way to fly to stay on course. When there are two such radios, this is the one labeled number one and treated as the primary.
Context Anchor
Seen in instrument cockpit equipment, electrical load planning, and standby-battery procedures.
Derivation
Navigation comes from Latin words related to moving or directing a ship, and radio comes from a word meaning a ray or beam. Together, the term points to using transmitted signals to help direct the aircraft along a course.
Why Pilots Care
It allows continued navigation and instrument approaches when the main electrical system fails.
Intuition Check
“#1” does not mean the radio is more accurate or always required. It identifies the first navigation radio installed or selected, separate from Navigation Radio #2.
Example Sentence 1
After the alternator failed, the pilot confirmed the standby battery was powering Navigation Radio #1 and continued tracking the VOR inbound.
Example Sentence 2
The checklist directed the pilot to keep Navigation Radio #1 on and turn off Navigation Radio #2 to conserve standby battery power.