Welcome Guest. Sign in or Signup

2 Answers

How to apply magnetic variation over a long distance

Asked by: 422 views Flight Instructor, Private Pilot

So on a short cross country trip I have been teaching to correct for magnetic variation by using one of the isogonic lines that lies about in the middle of the leg or trip. Is there a rule of thumb on how often to correct for magnetic variation on a much longer trip, say like 800nm? Where we live in Texas they change only half of a degree per isogonic line and so that would be quite burdensome to fill a nav log out with all those small differences.  Thanks

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.

2 Answers

  1. Skyman100us on Oct 24, 2017

    That is an excellent question. There is not a rule of thumb on how often to apply the variation correction. You would add or subtract the appropriate variation for each leg of the trip closest to the isogonic line as you have been teaching. It is doubtful you would teach your students to plan an 800nm cross country by simply drawing a straight line from point A to point B. Nor would the aircraft you are conducting your private pilot training in have the ability to fly safely for 800nm without a fuel stop.

    It would be a dis-service to your student(s) to teach them to skip steps in aviation because it is burdensome. Cross country planning is an important training tool and developing good habits early on will benefit your student for a lifetime. Your student may not limit their flying future to Texas so should he or she decide they want to fly somewhere other than Texas, say the NW or NE where there is 10-20 degrees of magnetic variation, the necessity of applying variation will be more apparent.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes

  2. KDS on Oct 24, 2017

    Your navigation log goes from departure to check point, to check point, to check point, to destination. So what is a long flight is actually a series of smaller legs. Take the midpoint variation for that leg. Besides the change in variation, you will most likely also encounter a change in forecast winds along the way.

    If you really want to blow your mind, read about “great circle routes” versus “rhumblines”. Then there are programs that will give you a series of points that approximate a great circle route by creating a series of rhumblines.

    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.