VOR alignment with flow track

[metzgergva]

I have made a flightplan going westbound towards San Francisco with a couple of VORs as waypoints.
I flew it in NAV mode and just tuned the VORs for backup. What I found was, that on all of them I always had the VOR pointing a bit more counter clockwise by a few degrees versus the map. To my understanding it should point to the VOR location which should be what the map shows and the FMS uses as reference point.
I had a little wind from a bit left or right on the nose, but that did not change the picture. Also the distance to the VOR did not have an influence on the deviation. Could this be a mag dev data issue?

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KA350_VORdev_05.jpg (60 KiB) Viewed 1743 times

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KA350_VORdev_07.jpg (61.61 KiB) Viewed 1743 times

[SAS443]

Not deviation. That error is imposed on the whiskey compass due to local mag. fields.
The FMS3000 has it's own mag.var database so it should account for any change in variation.
My theory (might be wrong ofc)
VOR*s magnetic reference are not updated that often.
ILC VORTAC has a mag declination of 16E (set in 1965)
The nearest Waypoint I could find was REANA (just north from ILC VORTAC) and REANA has a mag declination of "just" 11.7E

Just my 2c.

[metzgergva]

I gonna update the magdev table with the 2020 version just out and see if it is that.

[SAS443]

Not sure that will solve it.
I think it has more to do with the Navdata.
I looked up TPH VOR in the NGXu FMS, it has listed the MAG VAR as 12E, but IRL the station is calibrated 17E (again back in 1965)

The result is the following VOR needle offset, which "randomly" is about 5E (again East is least)

vorneedle.jpg (172.59 KiB) Viewed 1699 times

[metzgergva]

Okay so we have the same on the NGx as on the KA350.
I replaced magdev and it had no effect.
So it would be a NAV data issue?

[KenG]

What you are seeing is normal and happens in real life as well. The Navigation Database in the FMS has a location for the VOR and flies track to track. The VOR radials are aligned with magnetic north and surveyed every few years. This creates a difference in FMS Track and the VOR's radial that is most apparent the further away you are from the VOR. In one case at KMGM, we have a VOR approach where the FMS and VOR differ by 6 degrees.

The other issue in the real world is the cone of confusion over the top of the VOR means that the NAV radios cannot precisely locate the VOR as you pass over the station. This error is more evident the higher you are during station crossing. Thus in the aircraft, you will see the VOR sort of wrap around the aircraft as you fly over the station.

[jarek]

A bit off topic, but the problem with sim environment is that it is way more binary and ideal. Usually there is no "soul" in these models. RW needles are floating, shaking, are in constant motion. There are very few developers that care about details. One example of effort to have such soul in the King Air is ADF receiver. See what happens with the needle as you approach the station. Attention to these small details is a distinguisher between quality models and just candy looking, mass-produced stuff that just looks good on the screenshots. KA has its issues, but clearly for now, it is moving in the right direction to join the "premium club". If there is no demand for quality, it will not be there.

[metzgergva]

Thank you Ken for your explanation. I read about but never realized it as being that constant over five VOR on my flight. Therefore wondering what could it be. I have seen in real world variations and moving on ADF, but for VOR only when still very far away and weather influences.
If a VOR is not adjusted correctly, I would understand that if you use this VOR for navigation you would come in from a different angle if you fly it centered in the HSI and if you point the radial to the MAP position it would show a deviation on the HSI.
The only thing that would explain it to me that the physical position is not correct versus the navigation database. Or am I missing anything?

[KenG]

Yes, looking over your photos again, you are right it is a consistent 4 to 5 degrees left the entire time. I'll have to ask the devs to check the raw data coming in versus the needle indication.

-Ken

[metzgergva]

Appreciate that!

[tcarter.67]

Hi Ken, we see this behaviour also in TFDi B717. I know there is some interaction between the two companies, is it possible that there is some connection between the two products and technology? TFDi were aware of it and said a while ago they would fix it at some stage.
Perhaps if they don’t have the answers TFDi might be able to help out....
Cheers

[KenG]

Yes, it is being discussed and we are looking into it.

Please continue to be patient and thank you for the report and update about the B717.