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Different systems of radionavigation and approach
by Koala
Articles


VOR (VHF Omnidirectional Range):

Radionavigation system wich enables to know your axial position to the station with a radial. Many pilots prefer VOR to NDB because it is less affected by meteorological phenomenas.

Reception distance from 25 to 200 nautical miles approximatively. Précision 2 to 3° approximatively.
Blind zone area overhead the VOR.
Frequency from 108 to 118 MHz per even tenth.

If you want any more explanations about the VOR you can find them here.

NDB (Non Directional Beacon):

Roughly the same as the VOR but more affected by mteorological conditions.

Reception distance from 25 to 200 NM rouhgly. Precision 3 to 5° approximatively.
Blind zone area overhead station.
Frequency bandwidth 200 to 420 KHz.

DME (Distance Measuring Equipment) :

The problem with VORs or other equivalent systems is that no distance is given. The DME has been created to give distance informations to such systems, like VOR, ILS, etc.

For every VOR frequency, is given a UHF frequency, 110 different from channel 17 to 126.

A little more thing to know is that a DME gives the direct distance between a plane and a station : overhead the station, it will give the height.

ILS (Instrument Landing System) :

Precision landing system with different parts :
- The Localizer (Loc) wich gives relative distance from the runway axis.
- The Glidepath (Glide) which gives relative height informations from the normal slope of descent.
- A DME wich gives the distance from the runway threshold.
- 3 markers: Outer, Middle and Inner Marker.

Reception distance 25 NM for the loc, 10 for the glide, with a precision of 0,1° for the loc and 0,02° for the glide.
Frequency bandwidth between 108 and 111,9 per odd tenth.

The role of the ILS for a plane, is to intercept and center on the double emitted informations from the loc and the glide, whatever the meteorological conditions are. To do, we use in the plane a simple systems with two indicators which gives the difference of position between the axis and the plane :

Too high and too left : descent and turn right to join the axis.


Too low and too right : climb and turn left to join the axis.


On the glide, on centerline.

Finally, the three markers enable the pilot from looking the DME as he receives differents sounds when he passes each marker : he can concentrate more on the aircraft handling.
• The outermarker : 4 NM from the threshold, low sound at a moderated speed (three morse's lines).
• The middlemarker : 3500 ft from the threshold : "normal" sound with alternate dots and lines.
• The innermarker : 250 ft from the threshold, high sound at a fast speed (dots).

GPS (Global Positioning System) :

Very precise system, which enables to know your precise position at any time in the airspace with 24 satellites orbiting around the earth. Only four of them are necessary to get position (3 satellites) and time i.e. speed (with the fourth one)

With Fly! two courses for the use of the GPS are given in a pdf format with the simulator or a great cours (in french) by Denez, link here

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