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Using Vectors - Triangle Wind Correction

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  • Using Vectors - Triangle Wind Correction

    Hi all,

    Could you please explain me how should we solve exercise 9 on page 14/17 section 5.

    "You are heading 020 at 120 kt. Winds 090/10.

    What's your velocity over the ground?"

    Thanks a lot,


  • #2
    Hi Itay

    To solve this you need a protractor, some paper, a ruler and a pencil.

    Draw one line (vector) to represent your heading: 20 degrees right of north for the heading 020 degrees, and make the length of the line proportional to your speed; I used 120 mm to represent 120 knots.

    Then draw a second line (vector) to represent the wind, using the same scale. Make the origin of the second line the 'northern' end of your heading vector. The wind is from 090, so this second vector should be horizontal and 10 mm long to represent 10 knots of wind. The two lines should now look like a very elongated numeral 7.

    Now draw a third line (vector) joining the other two so you have a triangle. This third line is your track vector. Use your protractor to measure the angle from 'north'; you should find that it is about 15 degrees from the vertical so a track of 015 degrees. Use your ruler to measure the length. If you have used the scale 1 mm = 1 knot as I did, you'll find it is 117 mm long = 117 knots.

    It is always worth doing a 'common sense' or 'gross error' check. If you are flying 020, with a slight headwind and a crosswind from the right, you would expect your track to be a little left of your heading and your groundspeed to be less than your airspeed. In this case, both are true which is good news.
    Courseware Design Team


    • #3
      Thank you very much Rod.

      Is there a formula we can use in order to save time on the real exam?


      • #4
        Hi Itay

        Which 'real exam' are you referring to? There is no maths and physics exam, as such, just a progress check at the end of each topic.

        If you are referring to the General Navigation exam, then you might have missed the point of this module. The maths and physics module serves two purposes; one to satisfy a regulatory requirement that the school has checked that students have a 'sufficient level' of maths and physics knowledge before commencing ATPL studies, and secondly to provide those students who are lacking in confidence in these subjects with a resource to refresh their knowledge, so they don't struggle during their ATPL studies.

        This particular question puts vectors into an aviation setting, merely to provide some interest and show an application in your new 'real world'. This is not a technique you will be taught to use in general nav, although the CRP5 uses the same principles and you will be using that extensively.

        But in answer to your direct question, no there is not a formula you can use to save time.

        To quote an old flight safety poster "short-cuts in aviation can lead to the wrong thing being cut short".
        Courseware Design Team