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## Magnetic Variation

• 172_Freighter
• Topic Author

### 172_Freighter created the topic: Magnetic Variation

Hey guys,

Lets say hypothetically that you are flying between 2 points on a WAC, Point A is right on the line of 12deg E variation, whereas point B (destinatin) is on the line of 15deg E variation, which variation do you use for computing your FPT in magnetic degrees?

Cheers

• Posts: 1169

### Richard replied the topic: Re: Magnetic Variation

G'day,

If it was a flight with a single sector, I'd simply take the average variation between A and B which would be 14oE (rounded to the nearest degree) and use that. The error in heading at the beginning would practically be corrected by the error in heading at the destination. But, in the end, we're only talking about a heading error of a degree or so.

Alternatively, you could always split the flight into sectors and flight plan each leg using the local variation at that point. You'd tend to do this for a longer flight anyway in which case using an average wouldn't be necessary.

Cheers,

Rich

• Posts: 1962

### bobtait replied the topic: Re: Magnetic Variation

Very hypothecical 172_Freighter. We can get a bit carried away attempting to calculate a heading to plus/minus one degree. We take the greatest care to measure the flight planned track at the mid-meridian to get the most precise answer possible, then we apply the ARFOR wind [which is the met man's educated guess after examining the isobars on a synoptic chart, rounded off to the nearest ten degrees]. The forecast wind is TRUE, so we convert his true guess into a magnetic guess so as to get our very precise heading to fly on a DG that precesses. Another alternative is to keep the CDI on the GPS centered.

Bob

• 172_Freighter
• Topic Author

### 172_Freighter replied the topic: Re: Magnetic Variation

Gday guys and thanks for the replies.

Yes i know, it does seem a rather pedantic question, although after some of the questions that have popped it up in the cyberexams thus far, unsure of what to expect in the real exam, I thought I would delve a little deeper - you know what CASA questions are like!

• brentonrule

### brentonrule replied the topic: Re: Magnetic Variation

I like your CDI reference Bob - pitty CASA examinares don't have a sense of humour though. Totally agree with you - I have never had to correct a heading by 1 degree - or even 5 degrees for that matter. Oh well, as they say the theory is just that; theory. Onwards.

• 172_Freighter
• Topic Author

### 172_Freighter replied the topic: Re: Magnetic Variation

Just an update because I did end up with a question on this topic.

I answered true direction should be measured from the mid-meridian and magnetic variation also applied mid-route, or something to that effect and It didnt show up in KDR

• rossy

### rossy replied the topic: Re: Magnetic Variation

Hey 172, how did you find the actual exam? I'm doing mine next week and have absolutely no idea what to expect. Any tips/hints you'd like to share??

Thanks

• 172_Freighter
• Topic Author

### 172_Freighter replied the topic: Re: Magnetic Variation

In general I found the exam to be easier than I expected. Dont use that as an excuse not to study though.

Know your 1 in 60's, I would say ~ 8/30 questions were based on 1 in 60's, note these were all worth 2 marks each. For the rest of it, if you *completely* understand the content in Bob's book you will have no surprises in the actual exam. As a matter of fact for this subject, I found Bob's revision questions to actually be harder than what was asked in the real thing.

In the end I got 98%

• Posts: 1169

### Richard replied the topic: Re: Magnetic Variation

Woot! Great job and congratulations on the pass!