Preserving the Option for Long Term Use of the Instrument Landing System (ILS)

John H. Johnson and Chester B. Watts Jr.

Abstract:	Although the Global Positioning System (GPS) appears to have an ever increasing role in the future of navigation, research continues to provide contemporary instrument Landing System (ILS) options to meet the future needs for precision approach guidance. Developments in the areas of wide aperture antenna arrays to sustain or provide ILS service in multi-path environments are showing promising results. Implementation of a proven technique to reduce multi-path effects, which requires optimizing the modulation phase of a two-frequency localizer system, has yet to be effected in the United States. Further benefits in minimizing multi-path effects could theoretically be gained by the use of a three-frequency localizer system. Application of some or all of these improvements would provide a basis to consider extended use of the ILS. With the belief that Category I, II, and III precision approach requirements of the future can be met, the complex issue of radio frequency spectrum (i.e. available channel frequency assignments) remains in the forefront as the limiting factor when long term use of the ILS is addressed. Data are presented on two new B-S antenna systems: (I) a 270-foot aperture localizer system which is still under development but showing promise; and (2) a non-imaging glide slope system that will be tested for long-term stability before achieving Federal Aviation Administration (FAA) acceptance into the National Airspace System (NAS). Data are presented indicating an improved level of performance in a multi-path environment, realizable by optimizing the phase relationship of the navigation tones on a two-frequency ILS system. The theoretical benefit of utilizing a three-frequency localizer system is also presented.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	625 - 634
Cite this article:	Johnson, John H., Watts, Chester B., Jr., "Preserving the Option for Long Term Use of the Instrument Landing System (ILS)," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 625-634.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In