Magnetic Variation Errors on Sectionals?

[Travis Colby]

OK, this one has me really scratching my head.

I've been preparing for my knowledge test and am regularly scoring above 90% on the practice exams. On the last one I took I missed a simple question about a magnetic course. The question concerned airports in the DFW area and I used a sectional chart, subtracting the 4 degree east variation called for on the chart, and finished the calculations. I got the question wrong and noticed that the I foolishly misread the question that specifically said the magnetic variation was 7 degrees east. Re-working that question with the stated 7 degrees east gave me the answer listed as correct.

I then started to wonder why the FAA would give us a question with a different variation than printed on the sectional they gave us as an exhibit, was that just a cruel trick? I then used SkyVector to check the problem again, and they also have the 7 degree east variation. I checked other sources and they all come up with 7-8 degrees of variation. Why is that?

What am I missing here? The flight is right at the 4 degree east isogonic line on the chart, so I am really confused. Are there errors on the sectionals?

I just don't understand this one!

 

[Gucci Pilot]

Maybe the 7 degrees included installed compass error

 

[CTLSi]

OK, this one has me really scratching my head.

I've been preparing for my knowledge test and am regularly scoring above 90% on the practice exams. On the last one I took I missed a simple question about a magnetic course. The question concerned airports in the DFW area and I used a sectional chart, subtracting the 4 degree east variation called for on the chart, and finished the calculations. I got the question wrong and noticed that the I foolishly misread the question that specifically said the magnetic variation was 7 degrees east. Re-working that question with the stated 7 degrees east gave me the answer listed as correct.

I then started to wonder why the FAA would give us a question with a different variation than printed on the sectional they gave us as an exhibit, was that just a cruel trick? I then used SkyVector to check the problem again, and they also have the 7 degree east variation. I checked other sources and they all come up with 7-8 degrees of variation. Why is that?

What am I missing here? The flight is right at the 4 degree east isogonic line on the chart, so I am really confused. Are there errors on the sectionals?

I just don't understand this one!

The FAA changed the written a couple of months ago. They managed to mangle the test and exhibits such that many questions could not be answered given the exhibits etc. I missed two that way, and had them hand correct it and give me my real score a couple of months later.

If you suspect you get that on your written, dont be afraid to challenge it.

 

[ARFlyer]

OK, this one has me really scratching my head.

I've been preparing for my knowledge test and am regularly scoring above 90% on the practice exams. On the last one I took I missed a simple question about a magnetic course. The question concerned airports in the DFW area and I used a sectional chart, subtracting the 4 degree east variation called for on the chart, and finished the calculations. I got the question wrong and noticed that the I foolishly misread the question that specifically said the magnetic variation was 7 degrees east. Re-working that question with the stated 7 degrees east gave me the answer listed as correct.

I then started to wonder why the FAA would give us a question with a different variation than printed on the sectional they gave us as an exhibit, was that just a cruel trick? I then used SkyVector to check the problem again, and they also have the 7 degree east variation. I checked other sources and they all come up with 7-8 degrees of variation. Why is that?

What am I missing here? The flight is right at the 4 degree east isogonic line on the chart, so I am really confused. Are there errors on the sectionals?

I just don't understand this one!

The charts that are used on the written exams are sorely out of date. I've come across questions and charts that date back to the early 80s.

The best thing to do is memorize the answers.

 

[hook_dupin]

I assume this is figure 26. When I looked it up, I didn't even see a mag var value on the excerpt of the sectional they cropped. Check the actual knowledge test supplement, as some test prep providers have chosen to doctor actual sectionals vice use the supplement.

 

[ja_user]

Magnetic Drift, what makes you think the written question was done at the same time as the sectional that they gave you?

 

[48dodge]

Also if you're regularly getting above 90s, you're probably ready.

 

[Travis Colby]

I assume this is figure 26. When I looked it up, I didn't even see a mag var value on the excerpt of the sectional they cropped. Check the actual knowledge test supplement, as some test prep providers have chosen to doctor actual sectionals vice use the supplement.

Yea, my mistake was looking at an actual chart instead of noticing the 7 degree value in the question itself. I have that figured out for the test, but in a practical sense and in real flight outside the test, I am really confused with the fact that the variation called for in the area through numerous sources seems to be 7 to 8 degrees east (for example, SkyVector has an 8 degree east variation). The part I cant figure out is why all those sources say 7 to 8 degrees but my up-to-date sectional says 4 degrees.

(Even worse, the AFD for the airport directly on the 4 degree line says it has a 6 degree variation...)

 

[AggieMike88]

Having lived in Dallas area for most of my life... I don't think we have ever leaned THAT far to the left.

Google-ing for a copy of the supplement book found a newer version with improved graphics than the blue cover version. http://www.faa.gov/training_testing/testing/test_questions/media/sport_rec_private_akts.pdf

 

[FlyingMonkey]

are the questions on the test the exact same ones as on some of these pratice tests like Sporty's Study Buddy or Gold Seal Ground School?

 

[FlightTest]

Not that it matters for test prep, but SkyVector gets its magnetic variation data from the last magnetic survey done at the airport or navaid. That survey could be years and years old, 14 years in the case of KDFW. I would guess that is where the A/FD variation comes from as well.

You can check this yourself by plotting a flight from one airport to another and looking at the magnetic course it gives. Then reverse the flight. For many airport pairs, the two courses won't read 180 degrees different.

The sectionals get the isogonic lines from a computer model that is run frequently, not directly from physical readings. Implementing that model is fairly complicated so almost all the flight planning tools use the same method as SkyVector.

 

[Henning]

OK, this one has me really scratching my head.

I've been preparing for my knowledge test and am regularly scoring above 90% on the practice exams. On the last one I took I missed a simple question about a magnetic course. The question concerned airports in the DFW area and I used a sectional chart, subtracting the 4 degree east variation called for on the chart, and finished the calculations. I got the question wrong and noticed that the I foolishly misread the question that specifically said the magnetic variation was 7 degrees east. Re-working that question with the stated 7 degrees east gave me the answer listed as correct.

I then started to wonder why the FAA would give us a question with a different variation than printed on the sectional they gave us as an exhibit, was that just a cruel trick? I then used SkyVector to check the problem again, and they also have the 7 degree east variation. I checked other sources and they all come up with 7-8 degrees of variation. Why is that?

What am I missing here? The flight is right at the 4 degree east isogonic line on the chart, so I am really confused. Are there errors on the sectionals?

I just don't understand this one!

The Variation constantly changes, on maritime charts they put the annual correction adjustment in the rose as well. Very likely the Figure they use is decades old and they just updated the numbers in the question on a rewrite. Either that or you were looking at a new chart and a decades old question.

 

[RussR]

You can check this yourself by plotting a flight from one airport to another and looking at the magnetic course it gives. Then reverse the flight. For many airport pairs, the two courses won't read 180 degrees different.

This would happen even if there was no such thing as magnetic variation, due to curvature of the earth and the great circle route.

 

[Silvaire]

I don't believe it has anything to do with magnetic drift or old questions or errors. All of these tests have one or two questions that are specifically designed to trip you up and make it difficult to score 100% no matter how smart you are. In this case it was simply a matter of reading the question since the magnetic variation they wanted you to use was given. You of course know this now as you admit to "foolishly misreading" it. There are not enough of these "trick" questions to cause anyone to fail, just enough to prevent you from acing the test. Maybe it's done on purpose or maybe it's just an example of test writers getting bored

 

[48dodge]

One of the questions I missed was the boat vs plane right of way. On the test the boat and plane were reversed from all the example test sources. I knew the correct answer but guessed wrong because I thought I was simply misreading the question. I'm still not sure why floatplane questions are on the test.

 

[Henning]

One of the questions I missed was the boat vs plane right of way. On the test the boat and plane were reversed from all the example test sources. I knew the correct answer but guessed wrong because I thought I was simply misreading the question. I'm still not sure why floatplane questions are on the test.

Because you only take one written per level. You can gain a Seaplane or even Rotor license on the same written as an add on to your rating.

 

[MAKG1]

Get your information from within the test. Use the supplement, not the sectional. Some of these were written quite a long time ago, and variation can drift quite a bit.

 

[Matthew]

Get your information from within the test. Use the supplement, not the sectional. Some of these were written quite a long time ago, and variation can drift quite a bit.

Sounds like the advice my CFI gave me - it worked for my written and my checkride - "Only answer the question you are asked".

 

[JoeFromKS]

I just took mine, and there were several "gotcha" questions. It's the idea of picking the "most correct" answer. But on some of them all the answers are correct or none of them are correct.

I studied with the ASA prep book. Many of the questions were worded exactly as on the test. On my last practice I got 93%, then 82% for real. Oh well, a pass is a pass.

 

[Silvaire]

Because you only take one written per level. You can gain a Seaplane or even Rotor license on the same written as an add on to your rating.

I don't think there is such a thing as a Seaplane license, it's a rating and there is no written test for it.

 

[Henning]

I don't think there is such a thing as a Seaplane license, it's a rating and there is no written test for it.

That's my point regardless what you call it, you can add it without another written, your PP or CP written covers everything at that level (except IR), ME, SeaPlane, Rotorcraft, Glider, all the same written as add ones, you take it once. That is why you see questions covering other ratings.

 

[Travis Colby]

Get your information from within the test. Use the supplement, not the sectional. Some of these were written quite a long time ago, and variation can drift quite a bit.

Point well taken. Wilco.

 

[Silvaire]

That's my point regardless what you call it, you can add it without another written, your PP or CP written covers everything at that level (except IR), ME, SeaPlane, Rotorcraft, Glider, all the same written as add ones, you take it once. That is why you see questions covering other ratings.

Okay, I get you now.