![]() ![]() The ground-based TLS sensors detect an aircraft’s position by interrogating its transponder the ILS frequency transmitter then guides the aircraft along the approach path. … At some airports where the runway is shorter and ends at obstacles like water, an ILS localizer installation may not be possible that achieves the ICAO-required tailored width of 700 ft at threshold and a maximum 6.0-degree localizer course width.” 1Ī TLS can overcome these problems, ANPC says, because it uses existing airborne ILS localizer, glideslope and transponder equipment, and basic ground equipment - a transponder interrogator, sensors to detect an aircraft’s lateral and vertical positions and an ILS frequency transmitter. “Additionally, ILS localizer performance can be diminished by multipath from large buildings located on the airport property. However, the glideslope equipment sometimes is difficult or impossible to install at airport sites that are on or near rough terrain, “and in some cases, cannot be used without extensive earth removal to reduce errors induced by multipath, or ground-based reflections,” ANPC says. “These make up 80 to 90 percent of the world’s airports.”ĪNPC, the only manufacturer in the world of the TLS, received approval in mid-2010 from the International Civil Aviation Organization (ICAO) as a supplier of the system.īoth the ILS and the TLS are designed to provide pilots an approach path with exact lateral alignment and vertical descent guidance on final approach to a runway.Īn ILS uses ground equipment consisting of two directional transmitters - the localizer and the glideslope - as well as two or three marker beacons to provide additional positioning information. “There are many airports that would love to have an instrument landing system (ILS) but can’t for a variety of reasons, usually because of the surrounding terrain or runway length,” Mains said. Airports with short runways or those surrounded by rugged terrain are considered ideal sites for a transponder landing system (TLS), a precision approach system manufactured by the Advanced Navigation and Positioning Corp.
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