We'll go through them in order — Page 560, Lesson 556

We're looking at the answers to a set of navigation practice questions, and I want to walk you through the reasoning behind each one, because that's where the real learning is. We'll go through them in order. Starting with question 59, the answer is 'b'. This is a plotting question, so the solution is to solve it by measurement on the chart. There's no calculation to memorize here; you physically measure the bearing or distance on the chart to get your answer. Now, question 60, answer 'd'. Let's break this down. You have 120 nautical miles of horizontal distance to travel at a speed of 288 knots. To find the time, you divide distance by speed: 120 divided by 288 gives you 0.4167 hours, which is 25 minutes. In that same 25 minutes, you need to lose 24,000 feet. So, 24,000 feet divided by 25 minutes gives you a required rate of descent of 960 feet per minute. Question 61, answer 'a'. Here you need to lose 6,500 feet at a rate of descent of 1,000 feet per minute. That takes 6.5 minutes. Flying for 6.5 minutes at a ground speed of 156 knots covers a distance of 16.9 nautical miles. But, this is 6 nautical miles before the DME, so you add that to get a total distance of 22.9 nautical miles to start your descent. Question 62, answer 'c'. Question 63, answer 'd'. This one is a nice shortcut. It's a 9-degree change of latitude. You could work it out as 540 nautical miles and convert to kilometers, but there's a quicker way. Remember that 90 degrees of latitude change equals 10,000 kilometers. So, a 9-degree change is simply one-tenth of that, which is 1,000 kilometers. Question 64, answer 'd'. This is a great one about Mercator charts. The key thing to realize is that on a Mercator chart, meridians are drawn as parallel lines. Therefore, the total length of the 53°N parallel of latitude will be 133 cm, and so will the length of the 30°S parallel. Now, we find the departure from 180°E to 180°W at 30°S. Departure equals change of longitude times cosine of the latitude. That's 360 degrees times 60 nautical miles per degree, times cosine of 30 degrees, which gives you 18,706 nautical miles. You now have a simple scale problem: the chart length is 133 cm, the Earth distance is 18,706 nautical miles. This gives you a scale of approximately 1:26 million. Question 65, answer 'a'. The Sun would be at its Zenith. Question 66, answer 'b'. This is about compass headings. Find the true heading in the normal way, then apply variation and deviation. First, check that you've balanced the drift. When deviation is given as East or West, you use the rule: "Deviation East, Compass Least." However, deviation—not variation, only deviation—is sometimes quoted as plus or minus. In that case, the rule is that deviation is what you apply to the compass to get magnetic, not the other way round. So, East deviation is plus, and West deviation is minus. Question 67, answer 'd'. Question 68, answer 'd'. Question 69, answer 'c'. Here, 3 times 444 is 1,332 kilometers. Divide by 1.852 to get 719.2 nautical miles. This has obviously been approximated to 720 to give a 12-degree change of latitude, which takes us to latitude 02°S. Question 70, answer 'd'. The average great circle track is the rhumb line track. Question 71, answer 'd'. Remember that the distance from the Equator to a Pole is 5,400 nautical miles, which is a 90-degree change of latitude times 60 nautical miles per degree. So, the Earth's circumference is 4 times 5,400, which is 21,600 nautical miles. Alternatively, you can multiply 360 degrees—a meridian plus the associated anti-meridian—by 60. Question 72, answer 'b'. Question 73, answer 'a'. The rhumb line track from 70°S to 70°S is along a parallel of latitude, so it will be 090° True. However, the great circle track will 'cut the corner' and take the shortest route, which will be to the south of 090° True. You can draw it out on a Lambert's style projection, or try it on a globe to visualize it. That covers all the answers. Each one reinforces a key navigation principle, from time-speed-distance calculations to Mercator chart properties and compass deviation rules.