RK Bali, Air Navigation
Convergency: DGCA Air Navigation questions
Meridians meet at the poles, so a great circle crosses each at a different angle. Convergency is the angle the two meridians make with each other, found as the change of longitude multiplied by the sine of the mean latitude. Half of it, the conversion angle, separates great circle and rhumb line bearings.
Nearly all of the 32 questions are bearing tables to complete, plus a few that work back from a bearing to an unknown longitude. The count seen in exam sessions stands at 2.
Rhumb line bearings at the two ends differ by exactly 180 degrees; great circle bearings differ by 180 plus or minus the convergency. The great circle lies on the pole side of the rhumb line, which settles whether to add or subtract.
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Question 1 of 5
The angle between the true great-circle track and the true rhumb-line track joining the following points: A (60°S165°W), B (60°S177°E), at the place of departure A, is:
Question 2 of 5
The average true course of the great circle is 100°. The true course of the rhumb line at point A is:
Question 3 of 5
What is the standard formula for convergency?
Question 4 of 5
An aircraft passes position A (60°00'N120°00'W) on route to position B (60°00'N140°30'W). What is the great circle track on departure from A?
Question 5 of 5
A great circle track joins position A (59°S141°W) and B (61°S148°W). What is the difference between the great circle track at A and B?
27 more questions in this chapter
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