Are the runway and ILS headings in FSX True or Magnetic headings. I ask this because I am updating some bgl files in ADE for us in FSX and there seems to be some difference in opinions as to which are correct, true or magnetic. Also which are indicated in a Jepperson Chart.

All runway headings are magnetic headings. All ILS approach course headings are magnetic. Because FSX is stuck in the mid 2000's and the earth's magnetic field constantly drifts more current approach plates may show an approach heading that is a couple of degrees off from what FSX shows (unless you have updated FSX).

 

Also note that since runways are identified by the nearest ten degree increment on the compass some runways in the RW (and subsequently, on your approach plates) no longer have the same number as they do in FSX. Example: KSAT, Rwy 04/22 in the real world is still Rwy 03/21 in the original FSX.

Many thanks for your prompt reply. In ADE (Airport Design Editor) I am told that the headings are all True headings. May I assume the following:-

FSX and Jepperson Plates are all Magnetic (as you said). Therefore in order to bring the ADE airport bgl up to date and in line with the Jep. Plates I must change the RWY and ILS details to conform with the Magnetic headings and so bring the FSX airport to the correct configuration. Does the AIRAC cycle have any influence on this or is it solely concerned with the aircraft nav system eg. FMC. Also, can a ILS be offset to the runway center line  and if so what are the allowed amounts.

Runways and ILS localiser are aligned on true bearings and so don't change when magnetic variation changes. If the magnetic variation changes sufficiently the only real-world change is in the runway designation. changing that in FS will break any existing approaches to that runway.

 

The best solution is to update FS magnetic variation by from here http://www.aero.sors.fr/navaids.html

 

Officially ILS localisers may be offset by up to 5 deg from the runway centre line and still be classed as ILS. This has to be shown on the charts.

One last question I hope, but many thanks for your very clear explanation. Question is, from which source does the aircraft nav system (PMDG, IFly FMC/FMS) get the ILS information. If it is from the airport bgl file (AFCAD or other) then all is well and good, if it is from AIRACS cycle could also be well and good, but if there is a difference between the bgl file and AIRACS then problems could arise with the relevant FMC/FMS rejecting the ILS heading as wrong.

The FMC uses the AIRC navdata, the nav radios use the FSX data

One exception is the Canadian north, where runways are marked based on true heading. You have to go pretty far north so it may not be of any interest to you, but if you consult the areodrome chart, it will specify.