Originally Posted by
eckhard
As roadrabbit says, the VORs are not necessarily aligned with mag north. The difference between true north and the VOR reference is called declination in the USA. As far as I know, the declination can be adjusted from time to time.
I wonder how often the VORs are actually aligned with the current magnetic north.
My gut feeling is that the alignment itself is rather easy - just a software parameter in a program somewhere. But as you've noticed, there's lots of places where the VOR is referenced. Not only do you need to update all the approach and departure plates for any nearby airfields, but even airfield plates as far as 50 nm away may have their positions referenced to your VOR (magnetic) radial and distance, so their plates need updating as well.
That will make realigning a VOR a major undertaking, and I can imagine that that's only going to happen when *really* needed - for instance when it's outside the published tolerances for a VOR. Maybe after something like 10-20 years?