An aircraft flies on the Northern Hemisphere following an easterly direction to a destination aerodrome with a higher latitude than the departure aerodrome. A straight line is plotted between the departure and destination aerodrome to determine the shortest ground distance and the desired track. Which of the following statements is correct regarding this flight?
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A
Due to Earth convergency, the track direction will continuously increase during the flight.
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B
Convergency decreases with increasing latitude.
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C
As great circle tracks are plotted as straight lines, they do NOT have a changing track direction.
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D
Due to the increase in latitude, the final track angle at the destination will be higher than at the departure.
Refer to figure.
The datum of the track direction is a single point, the North Pole, into which the meridians, our local north, converge.
Because of this, the straight lines drawn on the Earth have different directions along their length. Due to the fact that the change of direction on a straight line is a result of the converging meridians, the effect is called, Earth Convergency.
Also, it is known that the shortest distance between two positions is a straight line and the track direction is the clockwise angle from each local meridian to the direction of flight.
The figure shows a straight line representing the shortest distance, crossing the local meridians at different angles as we move eastwards and at higher latitude. The track direction progressively increases from 35º, at the beginning, to 115º at the end, saying that we have a convergency of: 115º - 35º = 80º. It is still a straight line, but its direction changes depending on where it is measured. This is the situation we have on the Earth.
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