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Author Topic: GRID heading indication on ND  (Read 331 times)

Holger Wende

  • Join date: May 2009
  • Location: EDDM
  • Posts: 309
GRID heading indication on ND
« on: Mon, 15 Apr 2019 22:23 »
Hi,

What is the meaning of the GRID heading value on the ND in arctic regions.
In the PSX manuel page 313 e.g. the value 241.

I am climbing approx 80nm north ob BGTL.
True heading shows 321°, true track ~324°.
Mag heading 006, true track 008°.
When Heading reference switch is set to NORM the ND shows GRID 033.

I do not understand what this 033 value indicates. And what can I do with this value?
It does not seem to indicate the difference between mag and true north.

Thanks, Holger

P.S.
I am flying a route which I wanted to do for a really very long time: Roughly towards and around the magnetic north pole, just to see what my standby compass will do in this region.
Will it just drift around, tumble, tilt, ... I am just curious :-)


Toga

  • Join date: Oct 2017
  • Posts: 123
Re: GRID heading indication on ND
« Reply #1 on: Mon, 15 Apr 2019 23:41 »
Hi Holger,

Grid Nav is a polar thing whereby you plot tracks with reference to a fictitious meridian which remains constant across the polar region. Reason for this is the convergence of all meridians to the true north pole change constantly and significantly as you get closer to the pole. If you took a reference off a true meridian or a magnetic heading you would have to constantly change heading to remain on track. Consequently if you flew a constant magnetic heading you'd end up spiralling into the magnetic pole and way off track - unless it was a rhumb line track of exactly 090 or 270 as that way you'd be flying along a parallel of latitude. I'd post a picture as it's easier to understand but there's a decent video of it here:

https://www.youtube.com/watch?v=n4GDyTctVZM

In your example above:

Plotting aside, true heading and magnetic are superfluous and will constantly change as you move across the pole. It is your grid track that allows you to fly the great circle route across the pole.

It's a confusing concept to grasp and my knowledge is somewhat rusty but that is how I understood it in general nav during my ATPLs.

T
« Last edit: Mon, 15 Apr 2019 23:56 by Toga »

Hardy Heinlin

  • Moderator
  • Join date: May 2009
  • Posts: 10667
    • Aerowinx
Re: GRID heading indication on ND
« Reply #2 on: Tue, 16 Apr 2019 01:36 »
Hi Holger,

you can easily see the grid heading when you look at the arctic and antarctic maps on the Instructor screen. There your screen pixel rows and columns provide the grid. Every horizontal pixel sequence is aligned in grid west and grid east direction, and every vertical pixel sequence is aligned in grid north and grid south direction -- no matter where on the map, be it below the pole or above it, be it left of the pole or right of it. When you go from the bottom left corner of the map straight to the top right corner, you will maintain grid heading 045° regardless of your relative position to the pole. Your screen grid is the reference. From the bottom to the top it's grid heading 360°. From left to right it's grid heading 090°. In all quadrants.


Regards,

|-|ardy

Markus Vitzethum

  • Join date: May 2009
  • Location: Reutlingen, Germany (near EDDS)
  • Posts: 321
Re: GRID heading indication on ND
« Reply #3 on: Tue, 16 Apr 2019 07:51 »
Hallo Holger,

a long time ago, in PS1.3 days, Andrea Fontana wrote a "Grid Navigation Tutorial" (with some support by me). The tutorial still survives on the archive.org version of aerowinx.com. If you have PS1.3 still around :-), you can also watch the videos.

https://web.archive.org/web/20051103111423/http://aerowinx.com/downloads/Grid.zip

The password to the file was "turbulence".

But I admit, the youtube video is also doing a great job. But youtube was not invented back then. :-)

Markus

Holger Wende

  • Join date: May 2009
  • Location: EDDM
  • Posts: 309
Re: GRID heading indication on ND
« Reply #4 on: Tue, 16 Apr 2019 17:25 »
Hi all,

I thought I had understand the basics of grid navigation.
But it took a while to realize the value in the GRID box on the ND really indicates the heading in the grid.
And as Toga wrote, I fear I got confused by magnetic heading, true heading and grid heading.
But my sight-seeing flight via the approx. magnetic north pole to the geographic north pole was both entertaining and really instructive  :)
Knowing something in theory and having seen its behavior in PSX during a flight are quite different things - to me.

https://www.youtube.com/watch?v=n4GDyTctVZM
What a rich source of information, wow! Thanks for sharing this.

For those interested in more look into the Aviation Training Network at https://www.youtube.com/channel/UC1hofi8HECjJAIf-IZ3E-Pw

Quote from: Hardy
... your screen pixel rows and columns provide the grid ...
Ok, in connection with Togas link above I now understand the grid orientation. It seems the grid datum is the 0 deg meridian. This was a missing piece in my puzzle.
Thanks Hardy.

Quote from: Markus
...Andrea Fontana wrote a "Grid Navigation Tutorial" ...
Thanks, Markus, somehow this sounds familiar, but it's too long ago and although I collected a lot from the PS1.3 times this tutorial somehow slipped though.
I will definitely have a look into it (again).

Best regards, Holger

Toga

  • Join date: Oct 2017
  • Posts: 123
Re: GRID heading indication on ND
« Reply #5 on: Tue, 16 Apr 2019 21:30 »
No Problem Holger. I can also recommend these ATPL videos on youtube:

https://www.youtube.com/channel/UCh48QjK5BvMkIHeljWkbOBA

Very useful.