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DME Position?

P

paulg

Messages
35
Country
southafrica
Hello All,

I'm using FSX Planner & ILS GPS Approach Creator.
The first part using the creator worked fine - I now have a bgl
with the ils.
I need to add the ILS Equipment - using FSX Planner. I've inserted ILS,used the ILS Data Box to position the yellow arrow.
If I click on the box (DME), a DME is automatically inserted next to my arrow.
From what I have seen on default airports, the DME is opposite the base runway near the secondary runway.This can be moved with the mouse.

Where exactly do I position the DME?

Next is the Glide Slope - but that looks as if it lies in the same position as the DME?

Regards
Paul
 
scruffyduck

scruffyduck

Administrator
Staff member
FSDevConf team
Resource contributor
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34,854
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unitedkingdom
The default position for the DME is generally the same location as the localizer. I have also seen them co-located with the glide slope. If you don't have an actual location then I would suggest co-locating it with the localizer

The default location for a Glideslope is generally to one side of the runway part way down and to the left of the runway it serves.

This shows default positions for an ILS for R12. The basis comes from AFCAD originally

ScreenHunter_63.jpg


The localizer and DME appear a way from the end of the runway but this airport only has a short runway. The important thing is that the localizer and DME are on the center line of the runway and the localizer and GS face the plane landing
 
Last edited:
jvile

jvile

Messages
8,893
Paul

Jon has given you a picture of the 3 basic antenna's that make up a full ILS.

There are a few minor issues that must also be considered.

When FS places the antenna's they normally use the published Lat/Lon for each antenna that is found on many airport runway charts. This works for the most part but can also cause a problem.

The Localizer antenna (long feather) is always placed at the end of the runway as in real world. This insures that your CDI needle always reads the frontcourse of the ILS when on the approach and landing.

The Glide Slope Antenna (small green feather) is always positioned at the runway touchdown point. That means the published Lat/Lon is normally adjacent to the touchdown bars of the runway which is 1000 ft inside the runway threshold (when applicable).

When adding a ILS you will normally have to drag the GS symbol in order to position it correctly at the touchdown point of the runway. Left side of the runway is a favorible position for this antenna but it also depends on taxiway entrance to a runway. Many antennas are on the rightside of the runway so airplanes holding for takeoff do not interfer with blocking/distorting the signal.

In FS there is also a scenery GUID that cooresponds to these symbols. Go To any runway that has a stock ILS and at the very end of the runway you will see the Localizer antenna. The GS antenna is either left or right of the runway at touchdown point. These pieces of scenery only represent the visual antenna and it is the feathers that the radio gauges work with.

The DME square antenna is placed differently in FS.

In real world the DME antenna may not even be on the airport ground. THe DME antenna can be calibrated and positioned anywhere within a certain mile of the runway. THis is not possible in FS so we have to use some trickery.

On Approach charts it will show if the DME for a ILS is distance to the threshold of a runway or distance to the end of a runway.

If the Chart shows the DME distance is to the end of a runway we drag the DME square so it sits at the end of the runway. WE place the checkerboard building with the small antenna on top to the left or right of the Localizer antenna. This is the scenery GUID for the DME transmitter.

If the Approach plate says the DME is zero miles at the runway threshold we then drag the DME box to the beginning of the runway. We also place the checkerboard DME building left or right of the threshold for the runway.

We cannot calibrate a DME as in real world so the symbol must sit at the theshold or the end of runway.

AFCAD and all other Utilities place the DME symbol somewhere (normally at the end of the localizer feather) but it is up to us to move it to a location that simulates the actual precise mile reading to a runway.
 
K

kevtherev

Messages
141
Country
germany
If there is no information of the DME position on the plates can I assume that it is either at the threshold or runway end. Should the symbol always be placed on runway center line.
 
jvile

jvile

Messages
8,893
If you have the ILS DME approach chart then you should be able to see what end of the runway the DME is reading from. Look at the DME distance from the IAF and the FAF. Under that look at the distance to runway. If the numbers are the same the DME is co-located with the GS antenna.

If the distance in NM between the DME and the runway are different (about the length of the runway) then the DME is located at the end of runway. Example, If the DME at the IAF says 14 NM and the distance to the runway is 12.5 NM (add the numbers beteen each fix) the DME transmitter is at the end of the runway.

DME Transmitters are very seldom on center line of the runway. The antenna normally is small and sits on a 10-15 ft pole. For protection they are normally located at the GS transmitter or part of the ILS shack (red checker building) next to the localizer antenna.

In some Country's like England the antenna sits midway of the runway and then calibrated to read the runway end or threshold. This cannot be done in FS
 
Andrew

Andrew

Messages
783
Country
norway
jvile said:
DME Transmitters are very seldom on center line of the runway.
Click to expand...

Very true. But because FS and/or designer programs often places the ILS-DME at centerline, people think this is true, and we get totally wrong DME readouts in freeware as well as payware afcads. As you state, the ILS-DME's are most often to be found by the PAPI ligts/Touchdown Zone. I often end up placing the DME at the thin end of the GP feather.
 
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