What device is used to navigate using NDBs?

The device used to navigate using Non-Directional Beacons (NDBs) is the Automatic Direction Finder (ADF). The ADF receives radio signals emitted by the NDB, allowing pilots to determine the direction to the beacon relative to their aircraft's heading.

When the ADF is tuned to a specific NDB frequency, it points the aircraft towards the beacon. This enables pilots to navigate to or from the NDB, which is particularly useful for en route navigation, approaches, or holding patterns. The information from the ADF is displayed on the cockpit instruments, making it an essential tool for pilots flying in areas not covered by other navigation systems or for those instances when additional navigation aids are needed.

In contrast, the other devices mentioned, such as the Global Positioning System, Radio Altimeter, and Flight Director, serve different functions. The GPS provides satellite-based navigation information, the radio altimeter measures altitude above the terrain, and the flight director assists pilots with guidance commands. None of these devices are specifically designed to utilize NDB signals for navigation in the same way that an ADF does.