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3 Answers

Difference between VOR compass rose and magnetic course

Asked by: 4286 views General Aviation

I expected the heading on a victor airway from VOR to VOR to agree with the magnetic heading on sectional charts but they don't. Using a plotter on the sectional for the exact route gives a different result even after correction for variation. Is this due to magnetic shift since the VOR was installed?

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3 Answers



  1. Nibake on Jul 24, 2014

    The specific example is KMOT, MOT VOR. The difference between the VOR and true north is is 14 degrees, but the difference between true and magnetic is 7E, leaving a 7 degree discrepancy.

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  2. Best Answer


    John D Collins on Jul 24, 2014

    The VOR in question was installed in 1965 when the variation was 13 degrees East. In the intervening 49 years, the variation has changed to 7 degrees East. The VOR has not been realigned since 1965. Although the actual magnetic bearing is off by 6 degrees, the radials still span over the exact same course. For example, V491 is on the MOT 203 degree radial. To fly the airway, you still set the CDI to 203 degrees, but the no wind magnetic course is going to be 209 degrees. This is true of most VOR’s in the world, as the magnetic variation changes over time, unless the VOR is realigned, the actual magnetic course to fly the radial will change as well. To correct this is a big undertaking as once the VOR is realigned, all the radials for all the airways, procedures, fixes etc that use the VOR need to be updated.

    The original variation of the VOR is given a different name to distinguish it from the current variation. It is termed the VOR declination.

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  3. Nibake on Jul 24, 2014

    Got it. Thanks! That’s what I suspected I couldn’t make sense of any other explanation. I’ve noticed others that weren’t as far off, perhaps they were installed at other times.

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