How to use a graphic flight computer to find ground speed and true heading<br>Align the wind direction under the " true index " mark by rotating the azimuth plate. If the winds are from 330 ° at 20 knots, align 330 under the true index. Align the grid so the center grommet is over one of the heavy lines.
The graphic flight computer has a "true index" mark.
( z1 have :ARG0 ( z2 computer :mod ( z3 fly ) :mod ( z4 graphic ) ) :ARG1 ( z5 mark :mod ( z6 index :ARG1-of ( z7 true ) ) ) )