that represents the true airspeed. Read ground speed under the grommet. The wind correction angle is measured right or left of the center line. Be sure to count the degrees accurately — the value of each line changes at the 100, 150, or 250 knot arc, depending on the
Example: You have laid out a course on a sectional chart and measured it to be 090° true using your plotter. The winds aloft forecast calls for the wind at your chosen altitude to be 230° at 18 knots, and the performance data for the airplane says that you can expect a true airspeed of 125 knots at that altitude.
1.Set 230° at the TRUE INDEX.
2.Using any convenient starting point, mea- sure 18 units up from the grommet toward the TRUE INDEX and make a dot at 18 units (see Figure 22).
3.Rotate the transparent disk to bring 090° to the TRUE INDEX.
4.Move the slide until the wind dot falls on the arc for 125 knots (see Figure 23 on Page 32).
5.Read the ground speed of 138 knots under the grommet; the fact that the wind dot is below the grommet indicates a tailwind.
6.The wind dot is 5° to the right, indicating that the true heading should be 095°. Now all you have to do is apply local magnetic variation to derive magnetic heading.
If the upper winds forecast applies to your entire trip, simply use the wind dot in this manner with the true course for each leg.
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