Premise: 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.
Hypothesis: the center grommet is always over one of the heavy lines.