Solution for short runway and sloping terrain
Tuesday August 26, 2014 Short runways that end at a body of water, a cliff, or other obstacle cannot physically have an ILS localizer installed with the signal aligned within tolerance for course width. Or in other cases the ILS localizer would be well off the airport property boundary and in an area that would have to be purchased and controlled. The TLS is always installed near the approach end and off to the side of the runway. TLS provides a signal that is identical to an ILS, but does so with equipment siting that is different from an ILS. This opens the possibility for many airports to have a precision ILS approach that cannot obtain one with the traditional ILS equipment. The localizer width for traditional ILS is always dependent on the runway length and localizer antenna array placement. The technology of the ANPC TLS uses a configurable and virtual emanation point, which is why the TLS can be installed in these short runway conditions. This capability is inherent with the TLS. The localizer configurations shown are possible with the standard TLS siting near the approach end of the runway and all would comply with FAA and ICAO alignment, course width and displacement sensitivity.
The TLS can provide 700 foot tailored width at threshold and 6 degree course width using the standard equipment siting near the approach end of the runway. This characteristic of the TLS localizer can be set in a configuration file available to the TLS technician.
As another example the TLS can provide 700 foot tailored width at threshold with 3.5 degree course width.
In each example shown below the traditional ILS localizer equipment would have to be placed at the point labeled “virtual localizer point” which in each case would be very difficult or impossible to do. For TLS, it is a virtual point configured by the technician during the installation of the system.
An example of a case where the ILS localizer would be well off the airport property boundary and in an area that would have to be purchased and controlled.
Again, a traditional ILS localizer would have to be placed at the point labeled “Virtual localizer point”
Sometimes the terrain slopes down so far from the height of the runway that the ILS localizer has to be installed on top of large support structures that elevate the antennas to the runway height. This is not the case with the TLS since the virtual point technology permits siting the equipment easily next to the approach end of the runway. Some examples of these costly structures are shown below for some airports in South America and Africa. None of these very costly ILS localizer structures are needed if TLS is used instead:
Sometimes aircraft experience landing problems and cannot stop before the end of the runway and actually destroy the ILS localizer antenna. Everyone on board was safe after this rough landing, but the ILS antenna will have to be rebuilt before all-weather operations may resume. This will cause traffic delays and lost revenue plus the expense of repairing the ILS. The new ILS localizer will have to be flight inspected and that will be at least one full day with a flight inspection aircraft and crew. In this situation where the aircraft overruns the stop end of the runway, the TLS would not need repair since no equipment is located at the stop end of the runway.