Welcome Guest. Sign in or Signup

3 Answers

Difference between VOR compass rose and magnetic course

Asked by: 4809 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?

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

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.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes

  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.

    +8 Votes Thumb up 9 Votes Thumb down 1 Votes

  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.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes

The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.