Definition
The display field on an electronic flight display (EFD) or navigation radio that shows the currently tuned VHF navigation frequency, typically used for VOR, ILS, or localizer reception. It usually shows both an active frequency and a standby frequency, allowing the pilot to pre-select the next frequency before swapping it into use.
Plain English
The little box on the cockpit display that shows which navigation radio frequency you are using right now, and the next one you have lined up ready to switch to.
Context Anchor
Seen on an electronic flight display when a pilot tunes or checks the airplane’s navigation radio during instrument flying.
Derivation
NAV is a shortened form of navigation. Frequency means the radio setting used to receive a signal. Window here means a defined area on a screen, not a physical window in the airplane.
Why Pilots Care
It lets the pilot confirm the correct navigation frequency is active and quickly swap to a standby frequency without diverting attention from the instruments.
Intuition Check
Do not read window as a cockpit window. Here, window means a small display area on the screen where the selected navigation frequency is shown.
Example Sentence 1
Before starting the approach, the pilot tuned the ILS frequency into the standby side of the NAV frequency window and then swapped it into the active position.
Example Sentence 2
She used the NAV frequency window to select the next VOR frequency in standby before the handoff.