QEV 015 Grid Navigation (A)

How to solve Grid Navigation problems using geometric methods.
Google 'Cat3C i Books' for hundreds of practice questions with explanations and diagrams.

[@ahmadtheaviationlover1937]

this has to be the best youtube channel for atpl students!

[@Freezorgium]

I hate this part of GNAV so much.

[@hanookgill4471]

Perfect explanation and went through each thing step by step, making it easy to follow along

[@Deonvr1]

this makes understanding these types of questions so much easier :)

[@Cat3CATPLTraining]

+Deon van Rhyn Read the CAt3C iBook EASA ATPL Exam Passbook Part 2 -Charts for lots more examples and even easier methods of solving polar stereographic and grid navigation problems! itunes.apple.com/gb/book/the-easa-atpl-exam-passbook/id983799518?mt=11

[@Deonvr1]

+Cat3C I'll give it a try, still an endless struggle for me to calculate the longitude of the aircraft. Question states: "an aircraft has a grid heading of 310, using a chart based on a grid datum of 40 degrees. if the variation is 10E, and the heading 340 degrees, what is the aircraft longitude if the aircraft is in the Northern Hemisphere?" Answer is 0 E/W, no idea how they got to it

[@Cat3CATPLTraining]

+Deon van Rhyn I like it!! Where did you get this one from? Bit busy at the moment but I will get back to you asap! :-)

[@Deonvr1]

+Cat3C I got this question out of my Jeppesen ATPL Notes. Thanx a lot, much appreciated! :)

[@Cat3CATPLTraining]

+Deon van Rhyn "an aircraft has a grid heading of 310°, using a chart based on a grid datum of 40 degrees. if the variation is 10°E, and the heading 340° degrees, what is the aircraft longitude if the aircraft is in the Northern Hemisphere?" NOT a good question!! It does not specify the datum for the aircraft heading of 340°! Given that, under normal circumstances, if flying on a Grid Heading the only other heading to be specified would be a True Heading, a Magnetic Heading should not be considered. We use grid navigation where traditional magnetic navigation is too inaccurate for use. However, as magnetic variation has been mentioned we need to think that reality is being discarded in favour of academic number crunching! In fact, it only produces the given answer if we consider 340° to be a Magnetic Heading. So, applying variation of 10°E to 340°M we produce a True Heading of 350°T. The difference between the Grid and True Headings of 310°G and 350°T = 40°. This value is known as Grid Convergency. As True Heading is greater than Grid Heading the Grid Convergency is westerly (Grid Convergency West, True Track Best). Grid Convergency is the difference between the Grid Datum Meridian (GDM), in this case 040° (but we are not told if it is W040° or E040°) and the local meridian, i.e. the point where the bearing is being measured. But we know that the Grid Convergency is 040°W, which means that True North lies to the West of Grid North at the local meridian. The direction of Grid Convergency is measured FROM Grid North TO True North at the local meridian. The aircraft must be located 40° from the GDM, i.e. either at W080° or W/E000°. If the aircraft was located at W080°, transferring a parallel grid meridian from the GDM at W040° would place it to the west of the local meridian (W080°), i.e. anti-clockwise from W080°. The direction of Grid Convergency is the opposite of this, FROM Grid North TO True North at the local meridian; in this case, at W080° that is clockwise or easterly. However, if the aircraft was located at W/E000°, transferring a parallel grid meridian from the GDM at W040° would place it to the east of the local meridian (W/E000°), i.e. clockwise from W/E000°. The direction of Grid Convergency is the opposite of this, FROM Grid North TO True North at the local meridian; in this case, at the W/E000° meridian that is anti-clockwise or westerly. Therefore, the aircraft must be located at the W/E000° meridian. Sorry it's a bit long winded and no diagram but I will put together a diagram tomorrow (if I have time) and try to upload it to this post. Failing that, send your email to [e-mail] and I'll send it through the e-post! All the best, Tony :-)

[@taffpike4277]

No, the local meridian of longitude always points to True North, which is what I think you mean. Grid North is always in the same direction as the Grid Datum Meridian, in this case the Greenwich Meridian, which is pointing straight up 'the page'. Therefore, at W115: * the local meridian points to the True North Pole * the grid meridian is parallel to and pointing in the same direction as the Grid Datum Meridian, i.e. straight up 'the page'. Simple rules: Grid Datum Meridian = Greenwich Meridian - Grid North = UP the page Grid Datum Meridian = W/E180 Meridian - Grid North = DOWN the page Hope that helps

[@taffpike4277]

Gyroscopic compasses have been around a lot longer than you may think, apart from which, when people went to the North Pole in days of youre, they navigated by the Sun and the stars, which a certain EASA member state wanted included in the GNAV syllabus....and no, it was not the UK CAA!!

[@Walcar]

perfectly clear !

[@marciomedeiros1173]

Excelent video!

[@flapthrottle4394]

Hope you don’t mind if I ask questions... how did the pilots in the past navigate above the North Pole? (Or in the vicinity of the North Pole) without the use of a magnetic compass? True, magnetic grid.....everything depends on the use of the magnetic compass?

[@fulcrum2951]

Reminds me of my add math but with additional words

[@tazb3255]

Shouldn’t grid north always point to 000, you drew grid north in the opposite direction? Or am I mistaken.?

[@taffpike4277]

Go to atplontrack.com and see my other GNAV and other explanations. I will be adding more videos to atplontrack.com in the very near future.

[@islammofizul7545]

344°graud land rights to 180°r