Plain English Meaning

Equipment on the ground or in space that sends out signals pilots use to figure out where they are and where they're going.

Full Definition

Ground-based or space-based facilities that transmit signals enabling aircraft to determine position, track a course, or fly an approach. Common examples include VOR, NDB, ILS, DME, and GPS satellite systems.

Context Anchor

Seen in instrument flying when discussing what to use, cross-check, or replace if a navigation system or signal is lost or becomes .