Definition
An approach NAVAID is a ground-based or space-based facility that provides the guidance signal used to fly a published instrument approach procedure to a specific runway or airport. Examples include an ILS, localizer, VOR, NDB, or GPS/WAAS signal that defines the final approach course and, where applicable, vertical guidance. In the IFR alternate-requirements context, the term refers to the specific NAVAID that supports the instrument approach a pilot intends to use at the alternate airport, and that NAVAID must be forecast to be operational and usable at the estimated time of arrival.
Plain English
It is the piece of equipment that sends out the signal a pilot follows to line up with the runway and descend safely when flying on instruments. If that equipment is not working, the approach that depends on it cannot be flown.
Context Anchor
Seen in IFR alternate planning, instrument approach procedure discussions, and airport approach information.
Derivation
NAVAID is a contraction of navigational aid. The 'approach' qualifier narrows it to NAVAIDs that support an instrument approach procedure, as opposed to NAVAIDs used only for en route navigation.
Why Pilots Care
Confirms whether an airport meets the approach capability needed to serve as a legal IFR alternate, directly affecting flight planning and safety.
Intuition Check
“Approach” does not just mean getting closer to the airport. Here it means a published instrument procedure used to guide the aircraft toward a runway or airport.
Example Sentence 1
Before filing the alternate, the pilot checked NOTAMs to confirm the approach NAVAID for the ILS Runway 27 was in service.
Example Sentence 2
Loss of the primary NAVAID during the approach forced the crew to execute the missed approach procedure.