Depends on where you are flying.

If you are in Minnesota, USA it is 0 degrees, while here in the Seattle area it's something like -17 degrees.

So it depends...

cheers,
Joe

The only problem is that magnetic variation does indeed vary, that and FS9 has the Earth modelled as a cylinder rather than a sphere so it doesn't bother calculating it

Watch out for Marvin the Martian

ozzy72 wrote on Sep 6^th, 2011 at 9:09am:

FS9 does a fine job of modeling magnetic variation.

If you enter slew mode and press the spacebar your plane will be rotated to true north.

In Seattle (KSEA) your heading will be 340.

In Minneapolis (KMSP) your heading will be 357.

At La Guardia (KLGA), 013.

What FS9 does not model is the change of magnetic variation over time. This can make navigation with current charts challenging. There are files out there that will update the mag var, but they don't change any navaids or airports which creates another problem.

When using charts and a watch to navigate in the sim I chalk the minor discrepancies up to pilot error in adjusting for wind.

cheers,
Joe

machineman9 wrote on Sep 6^th, 2011 at 4:18pm:

If you slew>spacebar and your magnetic heading is 006, then determine your heading on the map and add 6 degrees for magnetic.

cheers,
Joe

ozzy72 wrote on Sep 7^th, 2011 at 6:52am:

Very true. I thought I was correcting to make the heading 000, but actually I need to ofset it to +006.


Cheers for that! I shall have to do a flight and practise flying through magnetic deviations.

ozzy72 wrote on Sep 7^th, 2011 at 6:52am:

That would only apply in some area where the variation is west of true north... unless you're talking about adding or subtracting positive or negative numbers.

In real life, and as modeled in FS9, the variation can be expressed in terms of "negative" for areas where magnetic North is East of true North (which means your true course heading will be a lower number on the degree scale than your magnetic heading), or "positive" when it is West of true North.

Of course, if you go past 360 degrees while adding or subtracting, that changes, but you have to visualize the circular scale, not a straight line. so, if you've laid out a true course with a heading of, say, 005 degrees true, and the variation is 10 degrees east, your compass heading to follow that course line needs to be 350 magnetic, because you subtracted 10 from 005.

On US charts, magnetic variation lines are labeled "xx degrees E" or "XX degrees W", so one has to figure the add/subtract thing every time.
Fortunately, there's another useful mnemonic for that:
"East is least, West is best".