WBryce,
Your first post is not correct. If you were given a magnetic heading of 032 and a magnetic variation of 10W your true heading would be 022.
Cadburys Dairy Milk Very Tasty works a treat and that is what I use. And to add to that, west is best and east is least also works, but it only works going one way, i.e. going from True to Magnetic to Compass.
The way to remember which was it applies, is think back to your PPL planning days. When you draw a line on your half mill chart you are plotting a true track. You then apply the foreceast wind and you end up with a true heading. What do you do next? You find the isoganol and apply the variation i.e. west of best east is least, this gives you your magnetic heading. You can then apply the deviation using the same process to get your compass heading.
Taking your example.
True Heading = 042
Variation = 10W (West is best, you add this to your true heading to get your magnetic heading)
Magnetic Heading = 052
Deviation = 3E (East is least, you subtract this from your magnetic heading)
Compass Heading = 049
If you draw a little table CDMVT (Cadburys Dairy.....etc) with columns and remember working from right to left is the conventional way you would work, i.e. PPL planning days. If you are working from left to right it is the reverse.
So lets say, using the above example you are given a compass heading of 049, deviation is 3E and variation is 10W, what would your true heading be?
CDMVT, but this time going from left to right, the reverse applies.
Compass Heading 049 and devaition 3E. Instead of subtracting (east is least) we add.
Magnetic Heading = 049 + 3 = 052
With 10W variation, again we are going from left to right you would subtract to get your true heading.
True heading = 052 - 10 = 042.
By doing a little table and remembering the sequence you can always do a gross error check going from right to left (once you have worked out the answers), if you are given the a compass heading first and asked to calculate a magnetic heading or a true heading.
Wow, alot of words there, hope its not confusing!
Last edited by CAT3C AUTOLAND; 15th Jun 2007 at 08:54.