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33
check came out to be 120 knots, and you calculate
the true airspeed at your altitude to be 140 knots.
1. Set 180° at the TRUE INDEX on the wind
side of the computer.
2. Move the slide until the grommet falls over
the line marked 120. The true heading is 20°
less than the true course, which means that
you have a 20° left wind correction angle.
3. With the grommet on the 120-knot ground
speed line, find the point on the slide where
the 20° left wind correction angle crosses the
line marked 140 and make a pencil mark (
see
Figure 24 on the next page).
4. Rotate the azimuth disk until the pencil mark
is on the centerline between the grommet
and the true index.
5. Determine the wind velocity by counting the
lines between the grommet and the pencil
mark.
6. Read the true wind direction under the true
index. You should have a wind direction of
104° and a wind speed of 50 knots (
see
Figure 25 on Page 35).
If you have GPS, the direct track readout is used
instead of true heading. Correct for variation, be-
cause the direct track information is magnetic.
Sample problems:
(Answers are on Page 38)
TRUE TRUE GROUND WIND WIND
HDG COURSE TAS SPEED DIREC. VELOCITY
1. 320 315 140 128
2. 175 160 150 115