VOR navigation problem [Resolved]

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jspa6m5
Posts: 16
Joined: Fri Feb 19, 2021 3:09 am
VOR navigation problem [Resolved]

Post by jspa6m5 » Mon Jan 03, 2022 12:08 pm

Hi,

I was a bit hesitant to post this question as I am 99% sure it is my lack of real life understanding rather than a specific issue with this aircraft. That said, coincidentally or not, this is the first time I have encountered it. To give you the scenario: I have filed a "stock" FSX flight plan for the Mivliz 737 from Baltimore KBWI to Detroit KDTW. The route is basically a direct VOR to VOR route. So my navigation log is obviously showing each VOR waypoint and the magnetic bearing from waypoint to waypoint.

So I am flying from waypoint to waypoint but if I am trying to follow the specific VOR radial bearing as shown in my flight plan, I am finding that the bearing I actually need to put into the course selector is quite different - perhaps 5 or 6 degrees different. Otherwise, if for example I am flying a magnetic bearing from VOR to VOR or 330 degrees and I were to put 330 degrees into the course selector for that VOR frequency, my flight path would end up several miles (at least) wayward of the planned route as shown on my backup GPS. Correspondingly if I simply follow the GPS route precisely (using the heading selector only) and "verify" that particular route by adjusting the course bearing for the VOR, again, it shows I am off by a good 5 or 6 degrees.

Now I can understand this discrepancy if I am flying from NDB to NDB where my heading is simply the direction my aircraft nose is pointed and therefore not necesarily the actual direction it is flying in (due to wind factors assuming perfect engine symmetrical power delivery, etc). But I am stumped with this discrepancy with the VOR.

The VOR should be accurate so long as my aircraft is on the desired radial heading towards that VOR regardless of what the wind might be doing in terms of where my nose is pointed and what corrections I might need as a result to the heading.

So in short, if my GPS, for example, is telling me that the current leg is on a bearing of 330 degrees to the next VOR and I am not that path precisely, then why would not the VOR course concur? Why does the course have to be "off" by such a large amount? Afterall, the GPS bearings like all the others I am using for practical purposes are magnetic.

I am only assume I am misunderstanding a basic concept here and that this is a user error or lack of understanding though as mentioned I have not encountered this issue before.

If you need screenshots as examples I am happy to provide though I would need to do the flight again. As things stand I have just been ignoring the VOR and course selection and simply "following the needle" with whatever wind compensation I need for the heading.

Perhaps an easier way to explain the issue is this: If I am perfectly on the magenta line shown by my GPS and the GPS says that this magenta line is on a precise magnetic bearing of 330 degrees from the next VOR I am travelling to, then why would inputting that same 330 degrees into my VOR course selector show the aircraft is NOT actually on that radial bearing? To me they should be precisely the same.

Thanks

jspa6m5
Posts: 16
Joined: Fri Feb 19, 2021 3:09 am
Re: VOR navigation problem

Post by jspa6m5 » Mon Jan 03, 2022 2:52 pm

Nevermind. I have figured it out - the GPS creates a great circle route and the VOR is of course a rhumb line. So I guess I would have to continually apply a conversion factor on my course selection if I am not wanting to "cheat" with the GPS but at the same time avoid the ATC from asking me to make course corrections, since the ATC also assumes I am flying great circles when selecting the VOR to VOR option.

I am interested how other sim users get around this though that is a different topic and not Milviz / 737 specific.

I found this video very helpful:

https://answeringatpl.com/conversion-angle/


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