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Mission Statement 

The purpose of FLAPS-2-APPROACH is two-fold:  To document the construction of a Boeing 737 flight simulator, and to act as a platform to share aviation-related articles pertaining to the Boeing 737; thereby, providing a source of inspiration and reference to like-minded individuals.

I am not a professional journalist.  Writing for a cross section of readers from differing cultures and languages with varying degrees of technical ability, can at times be challenging. I hope there are not too many spelling and grammatical mistakes.


Note:   I have NO affiliation with ANY manufacturer or reseller.  All reviews and content are 'frank and fearless' - I tell it as I see it.  Do not complain if you do not like what you read.

I use the words 'modules & panels' and 'CDU & FMC' interchangeably.  The definition of the acronym 'OEM' is Original Equipment Manufacturer (aka real aicraft part).


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Journal Archive (Newest First)

Entries in Herve Sors (2)


Magnetic Declination and Navigation Database Update

There's little point using real aircraft parts (OEM) when the underlying databases in flight simulator, that provide aeronautical information, are out-of-date.  A commonly encountered problem is: 'Why is the approach course on the simulator different to that published in the approach chart'

If wanting to achieve a high degree of realism when flying flight simulator, then up-to-date aeronautical information is vital. 

Navigraph strives to maintain the accuracy of their charts and database sets by releasing quarterly updates.  However, up-to-date data is pointless if the baseline navigational data in FS9, FSX or P3D is dependent upon outdated datum points, incorrect ILS data and runway identifiers, and various misplaced VORs and NDBs.  

The baseline navigational data that flight simulator uses is based on information that was available in 1988, and matching this dataset with any up-to-date dataset can cause navigational problems.  Furthermore, magnetic declination changes each year and after several years there is a major discrepancy in the accuracy of the data.  This discrepancy reports as incorrect approach course directions.  

File Location and 2017 Datasets

Flight simulator stores the aeronautical information as a. bgl file usually located in the scenery/base/scenery folder in the flight simulator route directory.  The file name is MagDec.bgl.  Replacing this file with an up-to-date MagDec.bgl file is very straightforward.

In January 2013, I wrote a similar article concerning this topic.  To review this article click here.  Since this date, the data has been updated.

Herve Sorrs (o-la-la)

No this is not a French dish served with snails (laughing). 

Herve Sors is well known for his work developing programs and add-ons that enhance the accuracy of the datasets that flight simulator relies upon.  His website is a treasure trove of information that explains the reasons why datasets should be maintained; in addition to being a platform from which to download programs.

Correcting Magnetic Variation

The Magnetic Variation Data (MVD) package provides an updated set of magnetic declination (Magdec) .bgl files as of January 2017.  Replacing the default magdec.bgl file with the one provided in this package will result in a much better fit between displayed headings and current documentation data (runway, ILS and procedure headings).

The MVD package can be downloaded from his website for free (PayPal donation welcome).  


Installation of the new MAGVAR.BGL files (copied from text file in the MVD).

(i)    Close FS9 or FSX/P3D, since you will not be allowed to replace the file while the simulator is running.
(ii)    Locate the MAGDEC.BGL file which is in the \SCENERY\BASE\SCENERY\ sub folder of your FS9/FSX-P3D install directory.
(iii)    Keep a copy of the old file.  Rename it MAGDEC.BGL.BAK (do not use a bgl extension if the file is kept in the same directory).
(iv)    In the provided package, select the updated file you want to use, either FS9, FSX or P3D.
(v)    Copy the new MAGDEC.BGL file in the \SCENERY\BASE\SCENERY\ sub folder of your FS9/FSX-P3D install directory.

Flight Simulator will rebuild its index at first launch and the new magnetic variations will be applied.

Updating NavAids (FSX and P3D)

To update the various NavAids, Herve has created a program called World Navaids (installer version 8.00).  This program comes with a self-extracting installer that provides an an easy to use interface to select, amongst other things, which NavAids you wish to update or install to which geographic region.  The interface also cross references the data and provides a conflict report if there is a discrepancy between the default and add-on scenery datasets.  Prior to any update occurring, the program will make a back-up of the existing dataset.

Final Call

Herve Sors has taken it upon himself to maintain the accuracy of the flight simulator database and to provide, free of charge, many small programs that enhance out simulation experience.  Thank you Herve for your contribution.  His website is Flight Simulator Aircraft Dynamics and Navdata.


Magnetic Declination - FS9 & FSX Navigation Datebase Update

Flight simulator whether it be FS9 or FSX, is quite long in the tooth as far as software programs go.  These programs was released several years ago and during this time span there have been many improvements in computer technology and in real world flying procedures.  When released, FS9 and FSX contained the latest navigational data, including the correct declination, VOR, and ILS radio frequencies; however, these are now out of date with real world counterparts.  

Magnetic Declination

Magnetic declination has a very important influence on air navigation, beginning with the use of the standard compass and sectional flight chart.  Similarly, radio navigation aids on the ground, such as VORs use magnetic variation to ensure reliable and accurate in-plane navigation.  The direction of the runway also relies heavily on magnetic variation and runway directions often require updating to ensure that ILS systems operate as designed. 

Simply explained, magnetic declination is the difference between true north and magnetic north and the value changes each year.  Flight Simulator is referring to a value that was accurate when the software was developed but has changed considerably in the ten years plus since the program was released. 

I realized a problem existed when I noticed that the direction of the runway did not align correctly with the latest navigational database installed into ProSim737 (Navigraph).   The CDU continually issued advisory warnings informing me that the runway direction and database were not identical.  Although it's possible to ignore the warning advisory, it becomes tiresome to continually reset the CDU  whilst in the more demanding phase of approach and landing.

Updating Magentic Variation

Updating this data is easy thanks to Herve Sors.   Herve has developed a free stand alone program that easily and quickly updates the magnetic variation in either FS9 or FSX whilst also providing the opportunity to rectify out of date and changed runway directions.  The information can be updated globally or by country region, and if necessary you can revert back to the old data.

LEFT:  Screen grab of program interface (click for larger view)

Without going into unnecessary detail, the program decompiles, corrects, and recompiles the necessary information within the .BGL files, located in the scenery folder of flight simulator; it's in this folder that the various navaids are recorded.

Do I need To Update ?

The ability of simulator to accurately simulate navigation is only as good as the navigational database installed.  Think of the database as a street directory or telephone book - do you want to search the directory for out-of-date information?  The update is a very simple process and takes but a few minutes and it's strongly recommended.

By updating virtual pilots will benefit at the very least from:

  • All VOR and NDB data will be up-to-date, allowing chart usage to easier with current charts.
  • Correct calibration of magnetic declination of navaids that provide an azimut information (VOR/VORDME/NDB) that will be greatly improved matching the "as real as it gets" experience while navigating (tracking navaid radials will be as it is indicated on charts).
  • ILS data (for those that are corrected, Europe only at this time) will be correct.

To download the required software (FSX World NavAids 4.32 & MagVar Data) and investigate Herve's various other programs, navigate directly to his website at AeroSors NavAids.

The software also updates the database for Prepar3D.