Those factors could be, for instance, another aircraft not vacating the runway, or a grizzly bear enjoying the winter sun on the threshold. If the runway is not in sight when the pilots reach the decision height, or some other factor makes a safe landing impossible, the pilots aboirt the landing and initiate a go-around. This decision height is predtermined by some factors like the outside visibility. This point in time is the decision height. There is a time in every final approach, when the pilot has to decide wether to continue or abort the landing. Now I want to explain the so called decision height to you. We have learned quite a bit about the instrument landing system. The instrument landing system benefits the pilots in bad weather, since the autopilot of modern airplanes can use it to automatically land the aircraft! MINIMUM – The Decision Height! Of course, the PFD is also able to visually show the glidepath to the pilots. At some airports, however, this angle can be as high as 5.5°, for instance at London City Airport. This path usually leads down to the runway in a 3° angle. The aircraft is on the ideal glidepath, if it flies right in the middle of those two signals. The glideslope employs a 90-hertz signal as a “too low” indicator and a 150-hertz signal as a “too high” indicator. The instrument landing system’s glideslope works in a very similar way. The flight deck’s primary flight display (PFD) can then show any deviation from the ideal flight path. The board computer now has the task to “find” this zero. The aircraft is on the ideal course to the runway, if the difference of those two localizer frequencies is equal to zero. The first two frequencies, sent by the localizer, superimpose each other. A third frequency can then be tuned in the flight deck. This system transmits two signals to the left and the right of the runway in different frequencies. The localizer antenna arrey is located exactly 300m behind the runway. Sub-assemblies for on site assembly of tower sectionsĪntenna brackets that allow adjustment of antennas both vertically and horizontallyĮxel poles and lattice masts can be applied to support localizer antennas, subject to the height and the size of the antennas.Instrument landing at Nuremberg, Germany, using the ILS! The tower is made of 5 m tall sections, with total height of 10 or 15 metres. Structures located within the graded portion of the runway strip not meeting the frangibility requirement, such as an existing non-frangible ILS glide path antenna, should be replaced by a frangible structure, if practicable, and relocated within the non-graded portion of the runway strip.Įxisting structures located within a distance of 300 m from the runway end not meeting the frangibility requirement, such as an existing non-frangible ILS localizer antenna array, should be replaced by a frangible structure or relocated beyond a distance of 300 m from the runway end.Įxel GP-tower follows the same lattice structure concept as the approach masts, but is made to cope with the demanding requirements of extremely high rigidity and frangibility. ILS Glide Path Tower and Localizer Supports Frangible Aviation Structures and LED Obstruction Lighting Specialists