Suppose a flight is to be flown from E to P. Draw a line on
the aeronautical chart connecting these two points; measure
its direction with a protractor, or plotter, in reference to a
meridian. This is the true course, which in this example is
assumed to be 090° (east). From the NWS, it is learned that
the wind at the altitude of the intended flight is 40 knots from
the northeast (045°). Since the NWS reports the wind speed in
knots, if the true airspeed of the aircraft is 120 knots, there is
no need to convert speeds from knots to mph or vice versa.
Now, on a plain sheet of paper draw a vertical line
representing north to south. (The various steps are shown
in Figure 15-21.)
Step 1
Place the protractor with the base resting on the vertical line
and the curved edge facing east. At the center point of the
base, make a dot labeled "E" (point of departure), and at the
curved edge, make a dot at 90° (indicating the direction of the
true course) and another at 45° (indicating wind direction). |
Step 2
With the ruler, draw the true course line from E, extending
it somewhat beyond the dot by 90°, and labeling it "TC
090°."
Step 3
Next, align the ruler with E and the dot at 45°, and draw the
wind arrow from E, not toward 045°, but downwind in the
direction the wind is blowing, making it 40 units long, to
correspond with the wind velocity of 40 knots. Identify this
line as the wind line by placing the letter "W" at the end to
show the wind direction.
Step 4
Finally, measure 120 units on the ruler to represent the
airspeed, making a dot on the ruler at this point. The units
used may be of any convenient scale or value (such as ¼ inch
= 10 knots), but once selected, the same scale must be used
for each of the linear movements involved. Then place the
ruler so that the end is on the arrowhead (W) and the 120-
knot dot intercepts the true course line. Draw the line and
label it "AS 120." The point "P" placed at the intersection
represents the position of the aircraft at the end of 1 hour.
The diagram is now complete. |