Refer to figure.
Convergency is the angle of inclination between two meridians at given latitude.
Convergency = Change in Longitude × Sin Latitude
The difference between great circle direction and rhumb line direction joining two points is called conversion angle and it is equal to half of the convergency for the same two points.
Conversion angle = ½ Convergency
Difference in Longitude = 170º
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Convergency is therefore:
170º x sin 60º = 147º -
The conversion angle is then:
147º : 2 = 74º
"A" and "B" lie on the same latitude, therefore, rhumb line direction will be 90º when flying east and 270º when flying west.
The great circle between two positions is on the poleward side of the rhumb line track. We are on the Southern Hemisphere, flying from east to west (B to A), our great circle track is initially smaller than the rhumb line track:
270º - 74º = 196º
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