Buzz
A graphic flight computer offers precise calculations for ground speed and true heading during flight. Knowledge of wind speed & direction, true course, and true airspeed is necessary.
Procedures
Adjust the azimuth plate to align the wind direction under the 'True Index' mark. For instance, if the winds are from 330° at 20 knots, align 330 under the true index.
Position the grid so the center grommet is over one of the heavy lines. The specific line used doesn't affect the procedure at this stage.
Mark the wind speed by counting from the center grommet. Each light line represents two knots. Place a dot or an X on the 20 knot line (two heavy lines above the center grommet) to mark the wind speed.
Adjust the grid until the wind mark aligns with your true airspeed. In this instance, the true airspeed is 120 knots.
Read the ground speed beneath the grommet. Ground speed, which is 138 knots in this case, represents the aircraft's speed over the ground.
Determine the wind correction angle (WCA) by measuring the angle between the center grommet and the wind mark. A rightward wind mark indicates a positive WCA, while a leftward one suggests a negative WCA. In this example, the wind correction angle is +4°.
Calculate the true heading by adding or subtracting the wind correction angle from the true course. For example, 175° plus 4° equals 179° for the true heading.
Adjust for magnetic variation and compass deviation to determine the compass heading for navigation. Magnetic variation is the variance between true north and magnetic north, and compass deviation is noted on a placard beneath the magnetic compass in the aircraft. Easterly variations are subtracted while westerly ones are added.
Tips
- Consider using electronic flight computers for these calculations, although they rely on batteries which may fail mid-flight.
- To determine actual wind speed and direction while flying, you can reverse the process using ground speed between checkpoints and the wind correction angle.
- If the wind mark is below the grommet, it indicates a tailwind; if above, it suggests a headwind.
Things You'll Need
- Flight computer with graphical interface E-6B.
- Writing instrument - Pencil.
