Montreal CYUL ILS data downloaded with TerraSync

[SurferTim]

I just found out about this. It appears some airports have ILS data downloaded with the airport data from TerraSync. Good deal! I saw this coming.

However, I ran into a problem with the ILS at Montreal CYUL. It has duplicate frequencies on rwy06R and 24L, and it causes loss of localizer near the airport.

[Isaak]

This is a generic issue with the same freq being used for opposing runways. It doesn't have an easy solution. In real world ops, only one of the ILS'es is activated at the same time. In FlightGear, both are enabled, so the system has to guess which one you're using. This becomes more difficult near or on the runway. Best practice is to be sure you have the runway in sight and autopilot deactivated before you enter this zone, then land manually.

[SurferTim]

The good part is the ILS data downloaded through TerraSync. That's gotta be an improvement over the static nav.dat files. It was just a surprise when I tried to change the ILS transmitter locations that the "old" ILS stuff wouldn't go away. Finally, I checked the TerraSync folder, and there it was.

It seems the ILS data priority is TerraSync, then local, then nav.dat if nowhere else.

I'm sure the developers will come up with a fix someday for the duplicate frequencies. In the mean time, I change the frequency on one of the ILS transmitters. In this case I used 110.4 on runway24L ILS. Not great, but it works.

If you have watched any of my videos on inclement weather flying, you must realize that losing the ILS on final could be fatal. Sometimes the first thing I see is the runway numbers and center stripe.

Edit: When I moved the localizer transmitters, I placed them about 1/3 down the runway. That should give pilots plenty of time to disengage autoland. If you can't see the center stripe by then, prepare to crash.
The localizer course becomes critical to get over the threshold, but i got it. I figure some day, FG will use the closest transmitter within a specific arc (120 degrees or so) of the localizer inbound course.
Just a thought.

P.S. Both the DME to the threshold and course to the ILS transmitter are already available in FG. I use them both in my Citation on the PFD.
After some thought, I guess you could leave the CATIII transmitters on the departure end of each runway. The DME is to that runway arrival threshold (other end of the runway). It won't switch until mid runway.

If 2 transmitters on the same frequency, I would use:

Code: Select all

Check within transmitter A arc (120 degrees of inbound course). If so, then A=true
Check within transmitter B arc (120 degrees of inbound course). If so, then B=true
If (A & B) then use lowest DME  (You are over the CATIII runway)
else if A, use A
else if B, use B
else red flags


Does anyone see a problem with that?

[SurferTim]

Just a FYI for those who modify nav data. If the airport ILS data is downloaded with TerraSync, you must edit that file in the /.fgfs/TerraSync/Airports/ folder.
If you don't, and remove it like I did, TerraSync will replace it and use it again next boot.

[wkitty42]

if you edit it, it will also be replaced by terrasync at next update of that tile data... the fix needs to be done to the file in terrasync so everyone gets it...

[SurferTim]

@wkitty42: You are probably right, but hopefully it will have been corrected. I'll take a guess that it will update that file when the new "last modified" date/timestamp value is newer than my edit...or at least newer than the original "last modified" timestamp.

Edit: In the case of CYUL, the runway needs to be moved if FG wants to maintain consistency with the real world. With the runway 06R moved to the correct location (30 meters north), the localizer may line up.
Also rwy06L is not in the correct location, even tho the ILS lines up. When moved (30 meters north), the ILS will no longer line up unless the ILS data is modified.

[wkitty42]

@wkitty42: You are probably right, but hopefully it will have been corrected. I'll take a guess that it will update that file when the new "last modified" date/timestamp value is newer than my edit...or at least newer than the original "last modified" timestamp.

if nothing else, the checksum will be different and that will trigger the update... terrasync works via checksums on the files contained within it...

[SurferTim]

I'll check that. It replaced the deleted file, but has not replaced my edited file. Maybe tomorrow?

[wkitty42]

it might be a once a day check... i don't recall and haven't dug into the code to see...

[SurferTim]

I just booted up. Started FG and launched the Twin Otter at CYUL rwy06R.
The changes I made 2 days ago are still in the file. The ILS lines up perfect on both 06R and 24L with my change. Well, unless somebody changed the TerraSync ils file.
However, the timestamp on /.fgfs/TerraSync/Airports/C/Y/U/.dirhash and CYUL-ils.xml were set to current time today when I launched the Twin Otter.

Edit: This is just a personal patch. Runway 06R/24L is in the wrong place. Needs to be moved approximately 30 meters north.
If I use the original ILS settings from TerraSync, it makes an approach to about where the runway should be.
For images of the approach, to where the runway should be, see:
viewtopic.php?f=17&t=40610

This is why I like the Twin Otter for ILS checks. Deploy the intake deflectors, and she'll off-road to where the localizer is centered.

[polly]

Moving the 06R threshold due north with the latitude setting in [myScenTerr]/C/Y/U/CYUL.threshold.xml:

Code: Select all

  <runway>
    <threshold>
      <lon>-73.741669</lon>
      <!--lat>45.456664</lat-->
      <lat>45.457564</lat>
      <rwy>06R</rwy>
      <hdg-deg>41.23</hdg-deg>
      <displ-m>0.0</displ-m>
      <stopw-m>0.0</stopw-m>
    </threshold>
    <threshold>
      <lon>-73.716667</lon>
      <lat>45.476664</lat>
      <rwy>24L</rwy>
      <hdg-deg>221.25</hdg-deg>
      <displ-m>0.0</displ-m>
      <stopw-m>0.0</stopw-m>
    </threshold>
  </runway>


, maybe a cit more than 100ft , moves the plane to the proper place on the
mpmap and in line with the unaltered location for th24L localiser. :


So the threshold locations tell the plane the startup points but do not repaint the runways, if we re-drew that threshold whatever number that latitude change represents then the new bearing ought to match the line between localisers.

[SurferTim]

I just checked TerraSync/Airports folder again, and it has changed the ILS position back to stock. I don't know how to disable the TerraSync ILS data.

[wkitty42]

I don't know how to disable the TerraSync ILS data.

you don't... if it is in the scenery files served by terrasync, then you get it...

[TheEagle]

Make a custom scenery folder and put the modified version of the file in there !

[wkitty42]

Make a custom scenery folder and put the modified version of the file in there !

you have to include all the other files for that tile in the custom directory, too... otherwise FG will find only the modified one and none of the others... yes, it stops searching once it finds the first directory that returns the files being sought...