Headings in FSX vs Plan-G

[erahmig]

Hi,

I have a question about the magnetic course values shown in the Track column of a printed Plan-G flight plan.

I created a no-wind flight plan in Plan-G, saved it, and also exported it into FSX format. After loading the exported flight plan into FSX I noticed that the Hdg value in the FSX nav log was consistently different from the value in the Track column of the printed Plan-G flight plan.

The Plan-G flight plan (PDF here, .plg file here) shows headings (Track values) as:

• 167
• 187
• 178
• 226

while the FSX nav log (PDF here, .PLN file here) shows headings as:

• 164
• 182
• 175
• 222

.

I thought at first it had something to do with magnetic variation, but the magnetic variation of that area is 8^o W.

When I actually flew the flight it was the FSX values that were correct - the Plan-G values consistently sent me too far off course to the right.

Am I missing something obvious that is causing Plan-G and FSX to disagree about the correct heading to fly?

Eric

[erahmig]

No one? Really?  :o

[tim arnot]

Sorry, I'm busy with the FSC conference right now. I can take a look at your issue when I get home next week.

[erahmig]

Hi Tim,

That's fine and completely understandable.

I didn't know that. Thanks for the update.

Eric

[tim arnot]

Plan-G uses the magnetic variation that has been encoded into the waypoints. If this is significantly different to the 'ambient' variation calculated from WMM2005, you will see differences in the headings calculated by both methods. This can often happen with addon scenery that has specified magvar from either WMM2000 or WMM2010.

[erahmig]

Hi Tim,

Thanks for the explanation. If I understand what you're saying, Plan-G uses whatever magnetic variation FSX reports for a given waypoint. That makes sense.

I don't have any addon scenery installed, just whatever came with FSX. Does that mean that all of my scenery is at WMM2005? If so, is there another factor that could account for the variation I'm seeing?

Eric

[tim arnot]

In Plan-G, you can see the difference in variation just by moving the mouse around -- both the ambient (ie WMM2005) value calculated for the lat/lon and also the values encoded into the waypoints are shown in the info panel. In the Faroes, the ambient is around 7.5-8 and the hard coded values are 10.

It's not normal  to see such a big discrepancy, particularly in default scenery, and I have no real explanation of why it should be so here.

[erahmig]

Hi Tim,

I don't know why, but I had never noticed the two different variation values before. You're right. At the AB NDB for example, the info panel displays 10^oW right under the NDB name, and further down in the info panel it displays 7.71^oW.

It looks like the FSX flight planner used the 7.71 figure and Plan-G used the 10 figure since the FSX flightplan shows 164 (157T + 7) and the Plan-G flightplan shows 167 (157T + 10).

Do you know of any way to mitigate this difference? Is there a Plan-G or FSX setting I could use to get rid of this effect?

Thanks for your patience with all my questions.

Eric

[tim arnot]

Not at the moment, no. And the issue has come up too late for anything to be done in 3.0. Maybe for 3.1...

[erahmig]

Hi Tim,

Ok, understood. Is there an official issue tracking system? I could write this up an an issue and point to this thread if you wish.

Thanks again for your answers.

Eric