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Given the:

True Heading = 070 degrees

True Track = 061 degrees

True Air Speed = 120 knots

Ground Speed = 118 knots

what is the wind variation?

these are the steps I am taking to calculate the wind variation:

1 - put the true heading on top - the true heading is 070 degrees

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2 - put the true air speed inside the little circle - the true air speed is 120 knots

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3 - mark the drift ( true heading - true track) = (070 - 061) = 9 degrees on that line

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4 - draw down to the ground speed (118 knots)

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5 - bring the little blue circle back to zero

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6 - rotate the disk so that the cross is on the central line

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there I can see that the wind comes from 151 degrees at 19 knots.

Questions:

will this always be correct?

Could I have calculated it through a formula (without using the computer)?

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    $\begingroup$ The flight computer is just helping you do trigonometry, It's fairly simple to do in something like excel, or just a calculator on your phone which has sin/cos/atan functions. $\endgroup$ – Jamiec♦ Dec 6 '16 at 9:31
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Sure it can. It's just vector math.

$$\vec{A} + \vec{B} = \vec{C}$$

If $\vec{C}$ is your ground speed vector and $\vec{A}$ is your airspeed vector (magnetic heading with true airspeed as a magnitude, then $\vec{B}$, the wind vector, can be solved for by

$$\vec{B} = \vec{C}- \vec{A}$$

Electronic flight computers and E6B apps for tablet computers/smartphones can do the same thing. But it's nice to have some basic skills with a whiz wheel.

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