PMDG database vs FSX database ILS glideslope problem

[redskins80 0]

I am currently using an addon airport VIDP from ImagineSim and having problems with the ILS glideslope.

I will try to add as many pictures and screenshots as I can to describe my problem.

Everytime I try to land on any runway, the glideslope brings me down much before the runway starts. This is valid for all the runways.

Even on FSCommander 9.1 the ILS feathers show the glideslope touching down before the runway.

 

Here is an image of how it looks on FSCommander:

I dont know whether this is an issue with the PMDG FMC database and/or the FSX navigation/GPS database or the airport addon itself is misconfigured,

Any help is appreciated. Thanks!

[scandinavian13 5,192]

The PMDG nav data is only the frequencies and the information about the ILS, so that's not the issue.

 

The issue will be with the scenery, as that's where the LOC and glideslope information is created, and what the sim uses to create the signals for the aircraft to follow.  I'd check with ImagineSim to see if they have an updated .BGL ("AFCAD") file.

 

By the way, those "ILS Feathers" (simism) are called localizers.

[redskins80 0]

Thanks for taking the time to reply.

Ill definitely check with ImagineSim for any more updates. They have given a few updates but it has nothing to do with this issue, ie it still persists.

In the meantime however, I'd like to ask you whether my decision to install an updated AIRAC for FSCommander and PMDG 737 could also be the issue? Since you said PMDG only contains the information regarding approaches, maybe that itself is wrong and hence showing up wrongly in FSCommander?

[scandinavian13 5,192]

You're welcome!

 

Nope. Again, the updated AIRAC information is simply telling the aircraft that the SIDs/STARs/Approaches contain these points (and their locations), locations of runways and airports, and the course and frequency information for the ILS.

 

Pertaining to the ILS data, it's like keeping my friend's cell phone number in my phone. That number has absolutely no location data associated with it, but if I called it, I could get his location and meet him somewhere.

 

Same with this situation: the navdata does not have any ILS location information stored in it. It needs to track the signal from the ground. This is how we engineered them in the real world: that signal is coming from a fixed and known location on the ground. Because even IRSs and GPSs have error in them, aircraft were never considered to be reliable enough to track approaches on their own, using their own position calculations (without ground-based signals like LOC/ILS, or later, WAAS), until recently with RNP approaches.

 

Same goes for FSCommander. No matter how incorrectly it displays the data about the airport (which I think it's getting directly from the sim, anyway - it's only the fixes/vors/etc that get updated through the AIRAC, but I can't say for sure). It has its own database, which is why you have to download a separate file. They're like address books. If I were to write down the wrong location for a friends house, it wouldn't mess up our mutual friends' address books.

 

The hard fact is that the localizer beam is coming from a set location in the sim.

While the localizer locations are stored as points in the navdata (so that they can be displayed on the ND visually), it has no bearing on the aircraft following the radio beams. I could head over to IAD right now, change a 737's navdata to show that IAD's 19C localizer (and associated glideslope) is somewhere in Kansas, but when they actually tune the frequency when near IAD, it will bring them right down to the runway, just the same as it did yesterday. Why? No matter what you change in the FMC, the signal to track is coming from the ground, not some calculation in the FMC.

 

Translating that to the sim:

The signal is coming from within the sim, which means the scenery within the sim. Since you've installed a new airport, that likely caused the problem.

 

If you'd like proof, try flying into another airport with an ILS. You'll probably find that it does just fine.

[Don t moderate me this way 882]

Screenshot(s) would help:

 

I never experienced this issue with IS VIDP. And your findings do not suggest an invalid FSX path registry entry.

[redskins80 0]

Alright so right now, Ive re-installed the airport and let fsx build its database. Then i let FSCommander re scan all the airports and that seems to have fixed the problem, atleast on FSCommander.

I will however fly the route as soon as i get time to confirm the glideslope's condition.

 

Btw, Thank you so much for all your help. You guys are pretty much the only people contributing in moving the FS world forward by helping us out. Brilliant stuff!

[fstulm 4]

Hello all, 

As Kyle said, the scenery is the issue. You can fix it yourself if you want; get a BGL (airport design software), open the airport and move the glideslope antenna approx. 1000 ft. past the RWY threshold. It is probably placed at the threshold or worse, before the RWY threshold.

I also noticed something very bad: the localizer antennas seem to be placed way before the RWY thresholds. What is going on here? Is it just a misrepresentation in FSCommander or someone is completely out of touch with what they’re doing? Those antennas should be PAST the entire RWY at the OTHER end.

Here is a method to check the Glideslope antenna:

1. Get a low seating aircraft – stock Cessna’s are perfect
2. Disable object collisions in sim
3. Put it at the TO position on the RWY – AKA on the numbers
4. Tune the ILS. At this point I don’t know if the glideslope indicator is visible or active as we don’t know yet what is going on.
5. If the slope indicator shows that you are below GS (horizontal bar up from middle) the antenna is ahead of you as it should. If not, continue the investigation
6. Put Sim in slew
7. Start moving backwards at slow speed and WATCH the glideslope indicator
8. If the slope indicator was down and at some point starts to rise, stop the motion immediately and see on the FS map where you are. At that moment you are where the GS antenna is – obviously in the wrong place if that’s the case.

Can’t wait to see what you get J I have designed an airport (including ILS and addition to PMDG FMCs) and it’s fun.

Ionut “John” Micu

[Mike777 163]

Possibly an earlier add-on AFCAD or scenery for the same airport?

 

Mike

[bpcw001 22]

Hello all, 

As Kyle said, the scenery is the issue. You can fix it yourself if you want; get a BGL (airport design software), open the airport and move the glideslope antenna approx. 1000 ft. past the RWY threshold. It is probably placed at the threshold or worse, before the RWY threshold.

I also noticed something very bad: the localizer antennas seem to be placed way before the RWY thresholds. What is going on here? Is it just a misrepresentation in FSCommander or someone is completely out of touch with what they’re doing? Those antennas should be PAST the entire RWY at the OTHER end.

Here is a method to check the Glideslope antenna:

1. Get a low seating aircraft – stock Cessna’s are perfect
2. Disable object collisions in sim
3. Put it at the TO position on the RWY – AKA on the numbers
4. Tune the ILS. At this point I don’t know if the glideslope indicator is visible or active as we don’t know yet what is going on.
5. If the slope indicator shows that you are below GS (horizontal bar up from middle) the antenna is ahead of you as it should. If not, continue the investigation
6. Put Sim in slew
7. Start moving backwards at slow speed and WATCH the glideslope indicator
8. If the slope indicator was down and at some point starts to rise, stop the motion immediately and see on the FS map where you are. At that moment you are where the GS antenna is – obviously in the wrong place if that’s the case.

Can’t wait to see what you get J I have designed an airport (including ILS and addition to PMDG FMCs) and it’s fun.

Ionut “John” Micu

 

Wow, I've got to try this.

I have a couple of payware airports where the ILS glide slope is off.

Flying such an ILS would either plant you into the ground before the runway, or let you overshoot badly.

[scandinavian13 5,192]

I must say, for anyone who is thinking they should go edit things, a few notes:

-NOT ALL glideslopes are 3 degrees (London City is 6 degrees, though the vast majority are 3)

-NOT ALL localizers are in line with the runway (Example - note the location in the airport inset)

-NOT ALL localizers are at the far end of the runway (though these are often in conjunction with #2)

 

For the United States, AirNav (or other sites providing the FAA IAPs) is a good reference for general LOC location and GS degree (this is shown in the profile view GS will be over TCH).

 

If you're looking for exact locations (for the United States), you should look into the DERS (it is free and contains all approach information, among other things):

http://aeronav.faa.gov/index.asp?xml=aeronav/applications/digital/dacs

 

You will find all LOC location data in the IAPFIX file within the ZIP.