Definition
A segment along an instrument route or procedure where the signal from a ground-based navigation aid is not strong or reliable enough to provide continuous course guidance, leaving a portion of the route without usable navigation information from that aid.
Plain English
A stretch of a published route where the navigation signal drops out, so the pilot temporarily has no reliable course information from that station along that segment.
Context Anchor
Seen in instrument procedure and route design discussions, especially where the FAA explains places where continuous navigation guidance may not be available.
Derivation
A 'gap' here means a missing piece — a stretch where the expected navigation signal isn't there. The phrase describes exactly that: a hole in the otherwise continuous course guidance the pilot is meant to receive along a route.
Why Pilots Care
Pilots must plan for these gaps by using backup navigation methods or adjusting altitude and routing to maintain safety.
Analogy
It is like driving through a short tunnel where GPS briefly drops out. The road has not disappeared, but the guidance signal is temporarily missing.
Grounding Statement
The key idea is a short break in usable course guidance, not a break in the route itself.
Intuition Check
Do not read “gap” as an empty or unprotected area where there is no intended route. Here, the route still exists; only the continuous navigation guidance is missing or unreliable for that portion.
Example Sentence 1
Before departure, the pilot reviewed the enroute chart and noted a navigational course guidance gap along the airway between the two VORs, planning to hold heading until the next station came in clearly.
Example Sentence 2
During preflight planning, the crew identified the navigational course guidance gap and selected an alternate route.