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Pe11e

Localizer deviation and other issues

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Last few flights I have starnge problem. For example on my last flight from UUDD to LTBA (Istanbul Ataturk) I requested vectors for 36L runway via Pro Flight Emulator, and in NGX FMC I could choose 35L. And on top of all ILS signal was completely off, airplane crossed the feather, and I had audible warning eather from PFE or FS2CREW - "localizer deviation!". Two or three times that warning repeated, before I had to switch off AP and do manual approach to 36L. Never had problem with localizer deviation neither heard that warning.

 

Now I'm confused what is causing this problem? I've just checked in ADE updated AFCAD version of LTBA from the AVSIM library that I used in this flight, everything seems fine, it has both 18/36 L/R runways with ILS approaches. So, my bet is that navigraph database that NGX uses is outdated and got confused, because stock LTBA airport doesn't have ILS approach for 36L. Also it's strange that in the navigraph database clearly says 35L/R!

 

Any suggestions and opinions on this issue? Should I possibly update the navigraph database?


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LTBA does not have runways 36L/R anymore - it has 35L/R. So your Navigraph database is correct and your scenery is outdated. That does not tell whether the database is outdated or not (it may be outdated but newer than your scenery - you should know that if you have updated it.

 

First - when in doubt - consult current charts for the airport. You can find Turkish charts at http://www.ead.eurocontrol.int/publicuser/public/pu/login.do (registration is required - it's free). They clearly show 35L and 35R approached.

 

Second - 35 ILS course is currently 355. It was 354 back in 2008. Strangely - it is coded as 001 in default FSX. I have no idea which course your scenery uses but if it is close to 001 - that is why you are out of ILS signal.

 

Third - there may be an issue with magnetic variation of your FSX or your scenery. FSX magnetic variation for Istanul is 3.3E. The current mag var in this region is 4.7E. I described magnetic variation problems and fixes here:

http://c-aviation.net/fsx-fix/magnetic-variation-in-fsx-problems-and-solutions/

 

 

What you should do:

1. Check your ILS course on FSX map - it it is far from 355 - you need a different scenery or you need to edit it.

2. If (or when) your ILS is correct and you still experience problems - update your mag.var.

3. If the problem persists - update ILS magnetic variation using aero.sors.fr tool.

 

It may be a good idea to look for a better scenery.


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The current designation is 35L.. so Navigraph is up to date for that runway.


Bert

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LTBA does not have runways 36L/R anymore - it has 35L/R. So your Navigraph database is correct and your scenery is outdated. That does not tell whether the database is outdated or not (it may be outdated but newer than your scenery - you should know that if you have updated it.

 

First - when in doubt - consult current charts for the airport. You can find Turkish charts at http://www.ead.eurocontrol.int/publicuser/public/pu/login.do (registration is required - it's free). They clearly show 35L and 35R approached.

 

Second - 35 ILS course is currently 355. It was 354 back in 2008. Strangely - it is coded as 001 in default FSX. I have no idea which course your scenery uses but if it is close to 001 - that is why you are out of ILS signal.

 

Third - there may be an issue with magnetic variation of your FSX or your scenery. FSX magnetic variation for Istanul is 3.3E. The current mag var in this region is 4.7E. I described magnetic variation problems and fixes here:

http://c-aviation.net/fsx-fix/magnetic-variation-in-fsx-problems-and-solutions/

 

 

What you should do:

1. Check your ILS course on FSX map - it it is far from 355 - you need a different scenery or you need to edit it.

2. If (or when) your ILS is correct and you still experience problems - update your mag.var.

3. If the problem persists - update ILS magnetic variation using aero.sors.fr tool.

 

It may be a good idea to look for a better scenery.

 

Thank you for detailed explanation.

 

I'm using latest version of PMDG NGX of course, and it includes the database from 2011. Just found this in ARPT_RWY.dat file in ...PMDG/NAVADATA:

 

AP;LTBA;ISTANBUL ATATURK        ;40.976167;28.814095;93
RW;05;40.966264;28.811320;93;11030;055;055;8530
RW;17L;40.996359;28.808525;157;11110;174;174;9842
RW;17R;40.996356;28.806031;163;0;174;174;9842
RW;23;40.977764;28.836156;90;11190;235;235;8530
RW;35L;40.969350;28.806978;102;11150;354;354;9842
RW;35R;40.969456;28.809470;100;11130;354;354;9842
 
So it has correct values for both runways, BUT I've just checked downloaded BGL of updated LTBA, and it has 36L/R, heading 180.xxx which is practically 001 in FSX.
Checked again what are my options in the library, and as far as I can see updated AFCAD from Ray Smith is from 2009, so it's outdated. My options are, either to use neewer payware LTBA or to edit runways in ADE, which can be tricky. I must admit this is pretty complicated, to many variables that could clash.

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RW;35L;40.969350;28.806978;102;11150;354;354;9842

RW;35R;40.969456;28.809470;100;11130;354;354;9842
(...)
So it has correct values for both runways

 

The values are close but not correct - they are 1degree off. Current ILS course is 355.

 

 

 

My options are, either to use neewer payware LTBA or to edit runways in ADE, which can be tricky

 

There is another solution. Edit ILS. You will get 5 degree offset but it should not be that hard to correct (there are ILS approaches with such an offset.

 

The other solution is to edit your database so that it has the same ILS location and course as in your scenery. You may need to alter some waypoints too.

 

 

For me it all requires too much attention. I would just set the ILS course manually and correct the route in HDG mode when intercepting ILS. Sorry - I do not have 737 yet so I can not tell you how to do it - but you can check it in your manual.


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And another solution should be to manually enter frequency and course instead of choosing ILS approach in the fmc. I will try that on today's flight.

 

Cheers and thanks for the help


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Just comparing FSX scenery to asatelite inage, the Nuzhet scenery ffor LTBA plus the runway designation fix by Okay pretty much fixes alignment issues, but the approach data wasn't updated AFAICT so FSX won't give you the approaches.  The fixed ILS localizer alignment is 358.48 which looks right from the sat image.  Note that FSX itself doesn't care about the deviation or courses as far as how the localizer "beam" is sent to your aircraft.  All that maters is the true heading and position in the ADEX data.

 

scott s.

.

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