Navigation systems performance versus civil aviation requirements

This paper presents comparative assessments of navigation systems in terms of their ability to satisfy current and projected civil aviation requirements. Emphasis is placed on U.S. operations. The navigation systems considered as candidates, either separately or in combination, for meeting post-1995 requirements are Loran-C, Omega/ VLF, GPS, VOR, DME, Doppler, and INS. Each navigation system is characterized by a brief description of the facilities used and the techniques employed in providing navigation capability. The technical performance capability of each navigation system is compared with both existing and projected system-use accuracy requirements. Of the two error components that determine system-use accuracy, flight technical error (FTE) and equipment error, it is shown that FTE is the limiting factor in the improvement of system-use accuracy. Each system is also evaluated to identify the limitations imposed by signal-coverage considerations. The paper concludes with the recommendation to maintain a navigation system mix of VOR, DME, Loran-C, Omega/VLF, and INS as an effective means of satisfying both current and post-1995 civil aviation requirements. Doppler is not included, because of its poor accuracy. It is considered premature at this time to make any commitments regarding civil implementation of the proposed NAVSTAR Global Positioning System (GPS).