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Instrument landing system glide path, commonly referred to as a glide path (G/P) or glide slope (G/S), is "a system of vertical guidance embodied in the
Instrument landing system glide path, commonly referred to as a glide path (G/P) or glide slope (G/S), is "a system of vertical guidance embodied in the instrument landing system
In aviation, the instrument landing system (ILS) is a precision radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to ...
which indicates the vertical deviation of the aircraft from its optimum path of descent", according to ''Article 1.106'' of the ITU Radio Regulations
The ITU Radio Regulations (short: RR) is a basic document of the International Telecommunication Union (ITU) that regulates on law of nations scale radiocommunication services and the utilisation of radio frequencies. It is the supplementation t ...
(ITU RR).ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.106, definition: ''instrument landing system (ILS)''
Principle of operation
A glide slope station uses an antenna array sited to one side of the runway touchdown zone. The GS signal is transmitted on acarrier signal
In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has ...
using a technique similar to that for the localizer
An instrument landing system localizer, or simply localizer (LOC), is a system of horizontal guidance in the instrument landing system, which is used to guide aircraft along the axis of the runway.
Principle of operation
In aviation, a localiz ...
. The centre of the glide slope signal is arranged to define a glide path of approximately 3° above horizontal (ground level). The beam is 1.4° deep (0.7° below the glide-path centre and 0.7° above).
The pilot (or the autopilot, if using autoland
In aviation, autoland describes a system that fully automates the landing procedure of an aircraft's flight, with the flight crew supervising the process. Such systems enable airliners to land in weather conditions that would otherwise be dangero ...
) controls the aircraft so that the glide slope indicator remains centered on the display to ensure the aircraft is following the glide path to remain above obstructions and reach the runway at the proper touchdown point (i.e., it provides vertical guidance).
Carrier frequency pairings
Localizer (LOC) and glide slope (G/S) carrier frequencies are paired so that the navigation radio automatically tunes the G/S frequency which corresponds to the selected LOC frequency. The LOC signal is in the 110 MHz range while the G/S signal is in the 330 MHz range. LOC carrier frequencies range between 108.10 MHz and 111.95 MHz (with the 100 kHz first decimal digit always odd, so 108.10, 108.15, 108.30, etc., are LOC frequencies and are not used for any other purpose). Two signals are transmitted on one of 40 ILS channels. One is amplitude modulated at 90 Hz, the other at 150 Hz. These are transmitted from co-located antennas. Each antenna transmits a narrow beam.See also
*Radio station
Radio broadcasting is transmission of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based radi ...
* Radiocommunication service
Radio communication service or radiocommunication service is according to Article 1.19 of the International Telecommunication Union's Radio Regulations (ITU RR),ITU Radio Regulations, Section III – Radio services, Article 1.19, definition: Ra ...
References
{{Radio station ITU Aeronautical navigation systems Aircraft landing systems Radio navigation Radio stations and systems ITU