Non-Directional Beacon (NDB)

September, 10, 2020 by

A non-directional beacon (NDB) is a radio transmitter at a known location, used as a navigational aid. NDB signals follow the curvature of the Earth, so they can be received at much greater distances at lower altitudes, a significant advantage over VOR. However, NDB signals are affected more by atmospheric conditions, terrain, coastal refraction and electrical storms, especially at long range.

There are four types of non-directional beacons in aviation, the last two used in conjugation with an ILS.

  • En route NDBs, used to mark airways

NDB bearings provide a charted method for defining paths aircraft can fly. This way, NDBs can, like VORs, define “airways”. Pilots follow these routes by tracking radials across various navigation stations.

  • Approach NDBs

A runway equipped with NDB or VOR (or both) as the only navigation aid is a non-precision approach runway.

  • Localizer beacons
  • Locator beacons

Most commonly used as markers for an ILS approach, NDBs may designate the starting area for an ILS approach or a path to follow for a STAR.

NDBs can also help plot fixes, by extending imaginary lines out from multiple navigation stations until they intersect.

References: SKYbrary, Wikipedia

Luca Caviness is an editor for the IFATC Education Group and an IFATC Supervisor. He is also a real-world student pilot.