ION Technical Content
DME/DME Accuracy
| Abstract: | Distance measuring equipment (DME) provides pilots with distance information between the aircraft and the ground station, and is used in all phases of flight. DME/DME RNAV is authorized for navigation on U.S. Area Navigation (RNAV) routes, RNAV Standard Instrument Departures (SIDs), and RNAV Standard Terminal Arrivals (STARs), where DME ranging from at least two DME facilities are used to determine the aircraft’s horizontal position. FAA requires RNAV-2 (2 NM, 95%, total system error, as a minimum standard for operating on RNAV “Q” routes), RNAV-1 (1 NM, 95% total system error) on SIDs and STARs. In this study, we will analyze the accuracy of DME/DME RNAV in the following steps. First, we analyze the accuracy of DME/DME RNAV in 2- D, where only two DME rangings are used. The accuracy of DME/DME RNAV depends on the accuracy of each DME ranging signals as well as the inclusion angle between the two DMEs used in determining the position. The DME/DME RNAV horizontal accuracy is plotted as a function of inclusion angle between the two DMEs. Next, we extend our analysis to include the accuracy of DME/DME RNAV in 3-D, where three DME rangings are used. Then, we look into several specific cases: a) two DMEs with a RVSM baro-altimeter as a third ranging sensor; b) two DMEs with aircraft at fixed altitude; c) two DMEs with a non-RVSM baro-altimeter. For these specific cases, the horizontal accuracy is a function of the DME/DME inclusion angle as well as the individual DME line-of-sight (LOS) elevation angle to the aircraft. The DME/DME RNAV horizontal accuracy for each case is plotted as function of inclusion angles and elevation angles. We limit the inclusion angle between 30 degrees and 150 degrees. When using ICAO DME accuracy error, DME/DME RNAV (two DMEs with a RVSM baroaltimeter) can achieve RNAV-1 when limiting the inclusion angle between 30 degrees and 150 degrees. When using FAA DME accuracy error, DME/DME RNAV (two DMEs and a RVSM baro-altimeter with maximum altitude of 60,000 feet and maximum DME range of 130 NM) achieves RNAV-2 and just misses RNAV-1 (can achieve RNAV-1 with the right mixes of adjustments in either inclusion angle, elevation angle, or maximum DME range). Finally, with the use of FAA DME accuracy standards, we show the region, where the navigation system error, NSE (95%) at the edge of inclusion angle (30 degree or 150 degree), meets the required RNAV-1 NSE (95%) level. This paper documents the results of this study. |
| Published in: |
Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA |
| Pages: | 443 - 451 |
| Cite this article: | Tran, Michael, "DME/DME Accuracy," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 443-451. |
| Full Paper: |
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