The "real world" mag var for my runway is 3.8, Airport 2.6 insists it is 5.1 and afcad reports it as 4.5Which one should should I use?David

I think it would be best to use the one FS uses. This will probably not be the real world one, as this data changes over the years.I wouldn't know wether Airport or AFCad reads the correct value from FS. Because I don't know how these two programs read the value I can not recommend one, but I guess I would go for AFCAD myself :).Arno

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The MagVar used to be embedded in a BGL in FS98 and I'd assume this hasn't changed with FS2002. It won't be current data so I would not enter current real world values if creating scenery. Best to stick with the values you get from the tools.If you are getting a variation between two tools it may be worth grabbing a third like FSSC or Architect just to "arbitrate" when a confliction happens.The downside of the locked variation is that FS is only correctly useable with approach plates valid at the time the variation was fixed.

The problem is, MS FS uses magnetic declination data for 1987.This info is stored in a special BGL within an array with 181 columns and 360 lines. Each line carries tha magvar for a longitude and every latitude, from -90 to 90 inclusive. Longitude ranges from 0 to 359deg (wraps around the globe, so 350 deg = 10 deg W).So your real world info will not match the one in FS, likely.Some programs have bad algorithms to read that array. I know FSSC can read it 100% correctly. Easynav2000 also, perhaps.In fact, I wrote some new magdec.bgl files with data for 2002 and different magnetic models. The problem is all VORs in FS need to be realigned with the new magnetic north position.

Thank you all for your input, I'll see what FSSC comes up with.David