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Runway alignments for ILS landings

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53 replies to this topic

#1 Tharmagon

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Posted 07 March 2013 - 12:02 PM

I have seen many discussions about the poor ILS alignment on some runways in FSX. From what I understand the magnetic headings change over time. And that MS just got some runway alignments just plain wrong ... or maybe they used data from elsewhere that was wrong. But what I don't understand is how to fix these problems so that ILS alignment is correct on most if not all runways.

One example I've been trying to fix is MKJP Norman Manley at Kingston Jamaica. In FSX runway 12 sits phyically at 119 degrees ... confirmed by sitting the aircraft aligned on the runway and looking at the heading. Yet the FSX ILS data seems to say that it is at 122 degrees and a few feet further to the right than the runway on screen. The Jeppesen plate says it is at 120 degrees. So I can only guess FSX has the visual runway on the screen wrong and the ILS data wrong. Would not be so bad if they were both wrong but the same - but they aren't.

I've seen many discussions about using AFCAD files to correct problems on an airport by airport basis. And using mag variation files. And using the latest data set from Navigraph. But what I do not understand is which of these I need, to correct these problems. Seems to me that if you corrected the alignment data it would still be wrong unless the visual runway was also corrected to match.

All I'd like is everything to be in sync - runway on screen, ILS data and FMS data for my PMDG 737. Even if they are all wrong at least get them so they are all incorrect but in sync. Can anyone tell me the easiest way to update everything ... if that is possible. What files do I need to get it all in sync?

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#2 GodAtum

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Posted 07 March 2013 - 12:14 PM

You could get the correct AIRAC by downloading Navigraph. But i dont think you can physically change the runway heading unless you get airport scenery.

11781474574_2439a62c68_o.png


#3 N60JBravo

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Posted 07 March 2013 - 12:22 PM

FSX data is old and can't be compared to current charts.

If you look at the attached screenshot you will see the localizer antennae at the tip of the red arrow.

[attachment=54421:MKJP.jpg]

For obvious reasons it can't be aligned with the runway, it would be out in the water.

FSX has the localizer in the right spot.

You can change this with ADEX if you wish, though it will no longer be correct.

regards,
Joe
The best gift you can give your children is your time.

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#4 Tharmagon

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Posted 07 March 2013 - 12:33 PM

Ok then is there a way to tell FSX that the ILS should be 119 degrees so that what is on the screen matches the ILS ... even if 119 degrees isn't really correct? I am not sure if someone has created a global bgl file to correct most of the alignment problems. I've searched and can only find files for individual airports. I did download and apply a bgl file for MKJP. But it didn't really help. Although it corrected the ILS to 120 degrees as it is on the plate, the visual runway is still at 119 degrees and a little to the left. So the aircraft tried to land on the grass to the right of the runway. If there were individual files available on an airport by airport basis that fixed the ILS and visual runway that would help. But I am not sure which files if any do that?

N60JBravo so are you saying that the ILS in real life is not aligned anyway? Then how do real pilots land using ILS if it takes them off the runway? Aircraft nowadays have autoland. That can't work if everything isn't aligned. Do real pilots know which are aligned and which aren't? An don non -aligned ILS runways, switch off AP and land manually? I am not a real pilot but would like to use correct procedures. How do real pilots do this? Can they somehow set an off-set in the FMS or something to make it all work?

These may be silly questions but I really don't understand how it should work. Just seesm logical that the ILS should take you right down to teh runway center line.

#5 RWFeldman

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Posted 07 March 2013 - 12:34 PM

What I have done is keep a list of incorrect ILS headings and use ADE to correct them or at least check them. I also keep the default fsx navdata, addon navdata and mag var. up to date the best I can.

Rendi

 

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Rendi


#6 Tharmagon

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Posted 07 March 2013 - 01:11 PM

Rendi,

That's good information. Where do I get updated files for the default FSX navdata and mag var? I know you have to buy the latest AIRAC data but not sure if that will help with this problem ... that is does AIRAC data contain updated ILS information?

Also can I change the ILS heading with ADE? That is could I just change the ILS heading for MKJP to 119 degrees to match the visual model using ADE? And maybe move it a little to the left so it hits the visual runway center line?

I am trying to learn a little here so please fore give me if my questions seem stupid. On the Jeppesen plate for ILS 12 at Manely it says the localizer is offset by 3 degrees to 120. And actual runway center line is 117. So I see what Joe was saying. But how do real pilots then do an ILS approach with an offset ILS like that ... especially in low visibility? I mean they will know the runway center line is offset by 3 degrees but if they can't see it until the last minute, how do they hit the mark, aligned correctly?

#7 tzombie

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Posted 07 March 2013 - 01:18 PM

Hello;

I had this problem with a couple of airports(add-ons),did a google seach,and found a updated -Updated Magnetic variation data for FS2004 & FSX.I installed this,and it fixed the issues.


Mark
Mark

#8 Zap

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Posted 07 March 2013 - 01:25 PM

You'll find some more good answers to your questions regarding this specific ILS approach in this thread too:
http://www.flycay.co...-ILS-12-at-MKJP
Simon

#9 mgh

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Posted 07 March 2013 - 01:41 PM

The Jeppesen chart dated 2010 states Loc Crs Offset 3o and Rwy Centerline 117o and is annotated OFFSET LOC. Microsoft has correctly modelled the ILS system here.

This is a Cat 1 runway and so pilots will make a final adjustment of course when the runway becomes visible.

Also, the ,link http://www.flycay.co...-ILS-12-at-MKJP is misleading. Only if the offset is greater than 3o is it classified as an LDA. That’s why the Jeppesen charts are headed ILS and not LDA

Gerry Howard


#10 Tharmagon

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Posted 07 March 2013 - 01:46 PM

Simon,
That link answers the problem with MKJP. That is what I have been doing. I actually set a fix at 119 degrees so I could see the extended runway center line. Then just lined up manually. I see on the plate it says the DA(H) is 278'. So it seems full ILS is not going to work as you say. I guess the only way to know if the problems are FSX problems or real world problems is to bring up the plate and read it carefully. As I said I am trying to learn to do it by the book. I guess in bad weather landing at MKJP is not an option.

#11 mgh

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Posted 07 March 2013 - 02:03 PM

I see on the plate it says the DA(H) is 278'. So it seems full ILS is not going to work as you say.


This is a Cat 1 ILS so the pilot must have established the required visual reference before the Decision Height/Altitude is reached. Otherwise a missed approach must be inititated.

Gerry Howard


#12 Tharmagon

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Posted 07 March 2013 - 02:12 PM

Well I guess real pilots do actually have to know how to fly and not just press buttons like some people think. I bet there are many runways that require a manual, visual landing ... probably most?

#13 N60JBravo

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Posted 07 March 2013 - 07:55 PM

N60JBravo so are you saying that the ILS in real life is not aligned anyway? Then how do real pilots land using ILS if it takes them off the runway? Aircraft nowadays have autoland.

Yes, many many ILS are not aligned perfectly with the runway so the pilot has to land the plane. that's what they (the pilots) are there for.

 

Autoland is not as popular in the real world as most sim pilots seem to think it is.

 

Most RW pilots would rather land the plane by hand anyway.

 

ILS come in several different flavors called categories.

 

You may see ILS approaches referred to as CAT I, CAT II,CAT III, with the differences being visibility restrictions.

 

Autoland is only allowed on CAT III and even then requires the crew have special training, which costs the airline extra money.

 

CAT III are rare due to the fact that most airports can't justify the extra cost for the limited times it would be needed.

 

How often due you think the weather in Jamaica is bad enough for any ILS to be necessary anyway?

 

regards,

Joe


The best gift you can give your children is your time.

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#14 ryanbatcund

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Posted 07 March 2013 - 08:37 PM

Well I guess real pilots do actually have to know how to fly and not just press buttons like some people think. I bet there are many runways that require a manual, visual landing ... probably most?

 

ILS isn't really for autoland.  It's the best way to get the plane through bad wx, and onto the runway with the lowest minimums.  Whether the pilots are using autopilot or hand flying... the ILS brings them through the weather to the runway safely.  

 

There are other approaches that do a similar thing, but pilots cannot be as low to the ground as with an ILS.  You might see an VOR/DME approach, or an NDB, or RNAV (GPS) approach.  They are all simply ways to get the plane through the weather and safely on the ground.

 

You are correct, there are many uncontrolled fields without any approaches.  There the pilot would have to fly a visual approach (assuming the weather is good enough) to land.


|Ryan Butterworth|

#15 scott967

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Posted 07 March 2013 - 08:58 PM

As concerns FSX, ILS data is part of the airport facility database files (APX files).  The ILS data record contains the true heading (front course) of the localizer antenna radiation pattern (where the deviation indicator needle is centered) as well as width and range, and a "backcourse" boolean which sets the localizer to radiate on the back course as well as front course.   I don't know to what extent the beam width and range is actually modeled, nor the characteristics of the back course signal (other than obviously it exists and can cause false captures).  So for the basic localizer operation (as seen in cockpit) there is no reliance on any sort of magnetic compass data as shown on a chart.  It's purely controlled by the geographic relationship of the sim antenna location and front course to the runway location.

 

Note that in FAA charts and I suppose ICAO as well, the course data that is provided is not kept current with actual magnetic variation (much like how runway numbers may not be exact).  I'm not sure exactly what triggers FAA to create a new chart, but the variation is recorded in whole degrees based on the variation given by a magnetic model that is updated at 5 year intervals, so the significant ones now are the 2010 and 2015 epoch.  I know I have seen an FAA NACO chart where there was a 1 degree difference in the final approach course on the ILS CAT I and ILS CAT II/III approaches.

 

Separately in FSX there is an approach data database in the same APX files as the ILS.  This database is formatted in a simplified version of the airline standard known as ARINC 424, which is a way of making the data on a chart computer compatible.  In that ARINC 424 data there are magnetic courses given, however for ILS approaches in addition to the magnetic course there is also a waypoint "target" so regardless of the database course compared to what a compass would read, the GPS display (and A/P lateral course following) will attempt to flyover or flyby the target waypoint.  In this instance runway threshold is treated as a flyover waypoint for the approach.

 

FSX AI use a very small subset of the approach data when doing an instrument/IFR approach.  In this case the stored magnetic course has significance (AI can't use the simulated antenna radiation pattern) but the AI engine is designed to align AI with extended runway centerline and aiming for threshold.

 

In-cockpit indications (compass/map/GPS) use a simulated magnetic variation from true based on a world-wide database of variations, magdec.bgl.

 

Note that VOR works a little different; a magnetic variation is stored in the database and this is used in the sim to determine where radial "000" is pointed..  So there is no expectation that a given radial will be followed by flying the identical magnetic compass course.  Again FAA only adjusts a VOR occasionally but it could be that the radials in the FSX VOR don't match current (I think this is a real problem in Alaska and there is a payware update out there for it)  

 

scott s.

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