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XWind conversion chart - wind components

MeganMac

Topic Author

MeganMac created the topic: XWind conversion chart - wind components

Happy Sunday y'all!

Can anyone tell me where the XWind conversion - wind component chart has gone? Its not in the ERSA. Where would I find it for my exam?

John.Heddles replied the topic: XWind conversion chart - wind components

If you want to be a little bit clever and save time, providing that you use a Jeppesen CR style computer, the whizz wheel gives you the numbers quicker and more accurately.

In the same way as you calculate the wind components for your normal navigation solution, you can do the same thing for simple crosswind and head/tail wind calculations.

Basis is that, for an angle between the wind and a direction -

(a) head/tail wind = wind speed x cos (angle)

(b) cross wind = wind speed x sin (angle)

The wind side of the CR has the normal CD slide rule scales on the outer edge but with the inner scale remarked with the angles for which the positions around the scale are the sine and cosine values. The TAS index on the inner scale is the usual "10" marked as "TAS" just for user convenience when setting up the multiplication.

So, if you align the TAS index with the wind speed

(a) run around to the right to the angle on the inner scale and read off the cross wind value on the outer scale

(b) run around to the left to the angle on the inner (black) scale and read off the head or tail wind on the outer scale.

(c) the whizz wheel is only marked to 45 degrees for cosine but, using the relationship sin (angle) = cos (90-angle) you can extend that (and higher angles for sine) by setting (90-angle) rather than angle - eg if you want cos (50) degrees, use the sin (40) mark, 60 degrees, use the 30 mark, and so on.

Examples. From the AIP table, for a wind speed of 60 kt,

(a) crosswind at 30 degrees is 30 kt, at 60 degrees is 52 kt

(b) head/tail wind at 30 degrees is 52 kt, at 60 degrees is 30 kt.

Check the CR whizz wheel and you get exactly the same values. Unfortunately, the usual Dalton whizz wheel (E6B) doesn't have the trig scales so you need the AIP table.

Engineering specialist in aircraft performance and weight control.