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Private Flying LAA/BMAA/BGA/BPA The sheer pleasure of flight.

10th Mar 2023, 14:47

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Hi all. I'm new to this site and have my first question. I'm studying Pooley's book on Navigation. One of the practice exam tests is, for me, difficult. I'll write that question below:

First, this is a question and answer I found on this website that's just like the Pooley's practice exam question:

This was an example given by a member here and he was Wrong!
E.g. An aircraft travels south along the same meridian from latitude 27°30'N to 02°15'S. What is the distance flown in kilometres?
27°30'N + 02°15'S = 29°45'
29°45' x 60 = 1785nm.....................HERE I GET 176700?????
1785nm x 1.852 = 3305.82 km

The Correct answer, after I saw it and checked it, is:

29 degrees, 45 minutes

60 nm = 1 degree

60 x 29 = 1740 + 45 for the minutes = 1785 nm

Now this is the Pooley's question:
An Aircraft is flying north from and to the following latitudes. I did the math but it's NOT one of the Pooley answers. Can someone tell me what the answer is and how they did that? So many thanks. Tom

05degrees, 30sec South flying to 32 degrees 30sec North

= 37 degrees, 0 minutes My Wrong Answer: 2220 km (37 degrees x 60 for 60 km in every degree of Latitude)
10th Mar 2023, 15:39

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Five and a half degrees plus thirty-two and a half degrees makes thirty-seven degrees? Back to essential maths class! Apologies, I was caught in the (intended?) trap: it is not five degrees thirty minutes, it it is five degrees thirty seconds. As neatly pointed out below by eckhard

BTW the Pooley's question does state "flying north" but without pointing out whether that is magnetic or absolute North. Tricky!
The other question is clearer: "along the same meridian" makes it clear that the orientation is absolute, not magnetic.

Last edited by Jan Olieslagers; 13th Mar 2023 at 08:35.
10th Mar 2023, 20:34

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32 degrees 30' + 5 degress 30' = 38 degrees x 60 = 2280 nm or x1.852 = 4222.56 Km
11th Mar 2023, 19:13

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Unless it's a typo, the fractions of a degree are in seconds and not minutes. So; 5 degrees, 30 seconds + 32 degrees, 30 seconds = 37 degrees and 1 minute.
37x60=2220nm. Add 1nm for the extra minute = 2221nm = 4113.3km
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13th Mar 2023, 06:59

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29°45' x 60 = 1785nm.....................HERE I GET 176700?????
I think you did this: 29.45 x 60 = 1767

You should have done: 29.75 x 60 = 1785 ​​​​​​​
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17th Mar 2023, 16:40

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There are so many different map co-ordinate systems; Just looking at my Sat-Nav gives me a choice of about 30 different Position Formats, everything from DD MM SS.S to Borneo RSD, Irish ITM, and many others.
The DD MM SS.S is the preferred Aeronautical method, but beware of the similar DD MM.MMM system used by some.
If you want to take height into account, then there are also several approximations. WGS84 is a popular Mapping Spheroid.

19th Mar 2023, 11:02

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Remember this: You won't have access to a calculator during the nav exam, and the exam is multiple choice. So you only need to guesstimate the correct answer with about 2-3 digits precision, and pick the right guesstimate from the four choices. Therefore when practicing for the exam, also don't use a precise calculator but try to guesstimate.

Furthermore, the CAA wants to test a few things with these questions:
1. You have a knowledge on how the worlds coordinate system works (latitude/longitude) and are able to perform some fairly basic calculations on this. Without a calculator, practically speaking the only calculations you can do are along a meridian (N <-> S, possibly crossing the North or South pole or the equator), or along the equator (possibly crossing the 0 or 180 degree meridians). Anything else requires fairly complex trigonometry and thus a calculator.
2. You know that 1 degree of latitude is 60 NM, or 1 minute of latitude is 1 NM. (Note that one degree along the equator is near, but not exactly 60 NM due to the earth not begin a perfect sphere.)
3. You know that 1 NM is 1.8 KM (rounded).
All three of these knowledge points can be combined in a variety of ways into a question but the question you quoted is the most typical example.

Armed with that knowledge, you already did a very good job and have nothing to worry about on the exam. Really your only mistake was that 29°45' (29 degrees 45 minutes) is 29.75° (29 and three quarters degrees), as already pointed out.
19th Mar 2023, 20:46

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Originally Posted by BackPacker
Remember this: You won't have access to a calculator during the nav exam, and the exam is multiple choice. So you only need to guesstimate the correct answer with about 2-3 digits precision, and pick the right guesstimate from the four choices.
calculators are permitted in the exam, providing they are of the approved type (
• Approved calculators (the approved models are: Casio FX 83/85/300 series; Sharp EL-W531/531 series; Citizen SR-260 series; Texas Instruments TI-30X/XB/XS))

Spot on with the guestimating- if nothing else it serves as a gross error check.

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