Ch 61. Navigation for Aviation
Aviation has long been in the forefront of developing the highest safety (integrity) navigation systems. It has allowed aviation to be one of the safest ways to travel and helped decrease the fatal accident rate in the US from about 1 in a million passenger miles in 1930 to zero in 2019/2020. To maintain this level of safety in the future, aviation navigation systems will need to evolve to support new entrants and new capabilities. New entrants include air taxis, personal flight vehicles, the growing numbers of Unmanned Aerial Vehicles (UAV) and even commercial space tourism. New capabilities include supporting operation in airspace that was previously unused such as low altitudes and in urban areas.
This chapter examines aviation navigation signals and technologies, focusing on those systems that will still have meaningful impact in development of the future airspace. It covers the systems currently forming the backbone of our aviation navigation infrastructure such as distance measuring equipment (DME) – see figure - and its military counterpart tactical air navigation (TACAN), VHF omni-directional ranging (VOR), non-directional beacons (NDB) and the instrument landing system (ILS). It also covers concepts for providing new capabilities using aviation infrastructure such as enhanced DME and Automatic Dependent Surveillance Broadcast (ADS-B) signals for navigation. Other concepts covered is navigation security and authentication and baro-altimeter use and errors (see figure).
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Figure 61-3. DME transponder response to interrogations from the aircraft DME avionics (interrogator). The transponder receives and validates an interrogation pulse pair. It then becomes unresponsive to other transmissions. After a fixed period (reply delay), the transponder sends a reply on the corresponding reply frequency.
Figure 61-17. Difference between GPS and Baro altitude on Balloon flight [Data courtesy Tyler Reid]
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