Incorrect Magnetic heading on flight plan

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Apologies if this has already been discussed, but I can find no mention of it in this forum. I was nearly caught out yesterday flying from KORS to West Wind (7WA3) in P3D.

The flight plan in Little Navmap calculates the magnetic heading as 084 degrees M. In the simulator GPS it was actually 042 degrees M.

I then used the Little Navmap measuring tool and the GC measurement was 065 deg T and Rhumb was 044 deg M. So the Rhumb measurement tool was closest to the GPS in P3D.

Just wondering where 084 degrees on the flight plan comes from?

Just wondering if I am doing something wrong or if this is a known bug.




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Hi Dave,

the great circle distance lines always use true course. For the rhumb line it depends if it starts from an airport or navaid. In the latter case LNM uses the magnetic variation of the airport or navaid and indicates "M".

I think the problem is caused by the incorrect magnetic variance on 7WA3 which I use to calculate the course for the flight plan leg.

The default 7WA3 has 19° East and the Orbx one has 19° *West*. Its next Orbx neighbor 4WA8 has 20°East which looks correct.

Should be easy to fix with ADE on "ADE_FTX_PNW_7WA3_West_Wind.BGL"

Magnetic variance is a big problem. Each airport and navaid has its own variance and sometimes there are more than 10 degrees difference between an airport and a VOR or waypoint nearby. Some airports far north have a variance of 0, etc. There are also files containing the variance for the whole world but I'm not sure if these are the solution.


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Hi Alex

Thanks for your explanation. I had no idea it was such a complex subject!

All the best



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