Slight magnetic heading discrepancy ?

[Elington]

Dear Tim,

I do love Plan-G and use it a lot for dead reckoning. So lack of accuracy is generally my mistake  :)
However I noticed this last week-end:
Building a flight plan from "KNUW" direct to "S97" gave me a true course 96° and a magnetic heading 75° (no winds) while the magnetic variation is 18° or so at both airfields.
If I'm not mistaken the magnetic heading should be 96° - 18° = 78°  ??? (which is what I get from the built-in FSX planner). I'm using build 2.02.481.

Please tell me if I can help or am doing something wrong,
Best regards,
David

[tim arnot]

The variation defined at KNUW is 21° E (in the AFCAD). This gives an initial magnetic heading of 075. The magvar embedded in the AFCAD overrides the area variation (because the early versions of Plan-G could not calculate the ambient variation). I don't know why the AFCAD should be 3 degrees different from ambient. (AirNav shows it should be 18°)

[Elington]

Hello Tim,

That explains the 3° thanks. Yep the Mag Var indicated with the airport info panel is different from the area variation.
Hadn't noticed that before. I just checked randomly outside of PNW: for instance "3SD6" has a 0° variation with
respect to 9° (!) in the area and so Plan-G gives magnetic heading = true course when starting a flight from there.
Sorry to ask :-[ but is this something you can fix? Anyway I'll double check from now on.

Best regards,
David