Australia Instrument Flight Rating (IFR) Practice Exam – Study Guide & Prep

The choice that indicates both NDBs must be within 30 nautical miles of the aircraft aligns with the operational limitations for accurate navigation using Non-Directional Beacons (NDBs). When using multiple NDBs to determine a position fix, proximity is crucial because the signal strength and quality deteriorate with distance. Beyond 30 nautical miles, the reliability of the bearings can be significantly affected by factors such as signal interference, terrain, and atmospheric conditions. This limitation ensures that the readings are accurate enough to provide a reliable position fix, allowing pilots to navigate effectively and safely.

The context of the other options involves the technical aspects of how NDBs function and how they are utilized in navigation. The conditions related to intersection angles and specific distances directly relate to the accuracy of triangulation methods used with NDBs. However, the key factor here is that the range limitation focuses on ensuring the signals are strong and clear enough to be used for navigation purposes.