Instrument Landing System (ILS)
The ILS activities include: sustaining engineering; new technology applications; and, modeling of the ILS signal propagation environment. The sustaining engineering activities resolved performance anomalies with fielded and operational localizer and/or glide slope systems. This work focused on providing solutions for systems that were performing inadequately or required excessive maintenance. Typically, these anomaly investigations required some form of analysis or mathematical modeling, field investigations consisting of ground and airborne measurements and site tests with portable or temporary navigation systems. The systems under investigation dealt with various configurations of localizer arrays and glide slopes including the optimization of the endfire system. The site investigations dealt with major airports such as LaGuardia, St. Louis, and Dulles involving all categories of operations (I, II and III) as well as smaller community airports such as Charleston, WV, and Cheyenne, WY. The anomaly reports contain problem identification, data measurements and analysis, and a description of the implemented solution with final test results.
The second area applies new technology to ILS systems to allow for an instrumented approach at airports where the current ILS systems would not provide adequate performance or meet the prescribed siting requirements. During this period, new initiatives included the development, implementation, and testing of the Redlich localizer array and the short endfire glide slope. Presently, both of these systems are part of the National Airspace System (NAS). In addition, initial work to modify existing antennas indicated the potential for a narrow-beam, bi-directional, log-periodic-dipole (LPD) antenna and a wide-horizontal-aperture glide slope antenna. Future work will focus on site performance and system evaluation to determine whether these antennas will meet all requirements. These reports contain the design, measured and analytic data, and system performance results. Mathematical models are a major tool to predict the effects of the siting environment on the localizer or glide slope performance. These models were used to identify the causes of anomalous performance, determine the proper type of ILS equipment for the given site environment, determine the terrain grading requirements for optimum glide-slope performance, and investigate the effects of snow on the glide-slope signal.
The ILS Team