What does NDB stand for in aviation terminology?

NDB stands for Non-Directional Beacon, which is an essential component in aviation navigation. This type of radio beacon emits signals in all directions, allowing an aircraft equipped with an appropriate receiver to determine its bearing relative to the beacon. The use of NDBs is particularly important for en route navigation and for guiding aircraft to airports, especially in situations where pilots might encounter limited visibility conditions or need assistance in locating their position.

NDBs are foundational to older navigation systems and continue to play a role in the aviation infrastructure, despite technological advancements with GPS and other navigational aids. The term "Non-Directional" highlights that the signal is not directed toward a specific location, allowing for a broader range of reception.

The other choices, while they include elements related to navigation, do not accurately represent the standard terminology used in the aviation industry. Thus, the correct choice reflects the established definition within the aviation lexicon.