VOR/TACAN course setting incorrect

[some1]

HSI course setting does not take into account the magnetic declination. Which causes CDI to show incorrect deviation from course.

For example here I'm parked on the runway heading 028 and tuned to LSV tacan at the opposite end. Bearing pointer shows correct direction to the beacon (25 degrees), yet CDI is centered when I set the course 37 degrees on the HSI, not 25. This difference happens to be the magnetic declination on this map (12 degrees). Same problem exists with VOR.

CDI should be centered when course setting is the same as bearing to station. The two pointers should align. VOR and TACAN use magnetic bearings.

 

Edited December 29, 2022 by some1

[gulredrel]

Thanks for reporting. I was wondering last time flying a certain radial abd coming in different than in a different aircraft doing the same. It was a different map so declination was smaller value.

[some1]

The issue is still present in the latest open beta in all three navigation modes: VOR, TACAN and also for RNAV. 

Basically CDI always shows the aircraft off course by the amount of magnetic declination.

[gulredrel]

Yes, noticed the same, but there was nothing mentioned in the patch notes, so I didn't expect it to be fixed.

[some1]

Yeah, but now that the GPS is fixed, the issue is also visible with GPS navigation mode. 

[Freefall231]

Thirded. Same issue. Noticed while validating some approach charts ingame and found the MB339 to be way off where it should be (mission set to same year as charts obv). Issue confirmed by flying same approach in a C101 where issue not present. Hope this gets fixed. Navigation a pretty big deal lol. 

Amusingly, put a portable TACAN next to a VOR, and program them both in the MB339 cockpit and switch VOR / TACAN nav and notice there's a significant difference between its position finding. 

 

Edited July 11, 2023 by Freefall231

[Freefall231]

Is this pretty major flaw going to be acknowledged at all, or is the MB339 just uninstall-ware now?

[6S.Duke]

Thanks for reporting, as per our code the HSI shows the magnetic direction but most probably there is some other hidden bug. We will have a check.

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[some1]

Hsi compass card shows magnetic direction indeed, but CDI deviation needle behaves like it's using true course.

[some1]

To better illustrate the issue.

How it should work: beacon at bearing 25, CDI centered when course set to 25.

 

How it looks in MB-339: beacon at 25, CDI centered when set to 37 (25 + magnetic declination of the map)

 

Edited October 22, 2023 by some1

[IvanK]

I think the CDI bar is referencing TRUE with Needle Magnetic ?

[some1]

 And it shouldn't.  VOR and TACAN radials are oriented to magnetic north. No HSI in real life behaves like that.

[gulredrel]

Hopefully this will get fixed soon:

"At the moment we are working to fix some annoying issues on the CDU and Custom Data Card and other issues related to the navigation, and we are finalising in parallel the flight director."

Has been said here:

 

[Ramsay]

On 11/23/2023 at 7:26 AM, some1 said:

it shouldn't.  VOR and TACAN radials are oriented to magnetic north.

Current HSI behaviour in DCS Open Beta is that 

VOR HSI course setting references Magnetic and takes Mvar into account

TACAN and RNAV HSI course settings reference TRUE

The HSI compass card it's self displays Magnetic heading and the AHRS/GPS CDU TRUE

Although the AHRS/GPS uses TRUE for it's internal calculations like an INS aligned to the rotation of the earth / TRUE North - it'd would make sense that Magnetic bearings are displayed to the pilot to be consistent with the HSI (magnetic) heading and information/signals i.e. Tacan/VOR radials usually reference magnetic North. However the exact MB-339A behaviour would need confirming with a SME.

Tested in Caucasus and Nevada maps, DCS Open Beta Multi-thread 2.9.1.48335

[6S.Duke]

Hi, thanks for reporting, we will have a look

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[some1]

57 minutes ago, Ramsay said:

VOR HSI course setting references Magnetic and takes Mvar into account

No, VOR is equally broken. You can test it in the attached mission by tuning into 116.90Mhz McCarran VOR. 

 

57 minutes ago, Ramsay said:

Although the AHRS/GPS uses TRUE for it's internal calculations like an INS aligned to the rotation of the earth

AHRS is not an INS. It cannot sense true north and it is not doing any calculations related to that. The only sensor it has to orient HSI is magnetic.

GPS has a built in magvar database (it can even display magvar to the pilot) and is perfectly capable of displaying magnetic bearings and course deviation. In fact, it already correctly outputs magnetic waypoint bearing for the HSI needle, but not the course deviation for the CDI. 

It makes absolutely no sense to steer CDI using True as it does now.

mb339_fail.miz

Edited November 25, 2023 by some1

[Ramsay]

1 hour ago, some1 said:

VOR is equally broken. You can test it in the attached mission by tuning into 116.90Mhz McCarran VOR.

As said, I took time to test in both Caucasus and Nevada maps, I do not see an issue with the VOR HSI course deviation in the current Open Beta.

I do see the problem with TACAN and RNAV i.e. using RNAV to LAS, I would set the HSI course to 212° to zero the deviation.

Edited November 25, 2023 by Ramsay

[some1]

Ok, so it looks like for VOR the CDI is correct, but the HSI bearing needle is not. These two needles should align as I explained in the first post. The bearing needle should point to 200 on the HSI, yet on your screenshot it points to 188, which is neither magnetic nor true bearing to station. 

The GPS showing true bearing to waypoint (BRG 211) also contradicts what's written in IndiaFoxtEcho's own MB-339 manual:

[Dataduffy]

Is there any estimated timeframe for fixing this issue?

I just purchased the aircraft and love it , but not being able to navigate tacan approaches etc, just ruins it for me.  

 

[6S.Duke]

Now should be fixed.

We will include the fix as soon as possible.

[Dataduffy]

thanks for the quick answer, and it's great to hear that there is a fix to arrive soon.

Much appreciated. The aircraft is great and with this fixed, I will fly it a lot more I'm sure.

[Ramsay]

On 12/2/2023 at 10:55 AM, 6S.Duke said:

Now should be fixed.

We will include the fix as soon as possible.

Testing with the latest Open Beta 2.9.2.49629 - this doesn't seem fixed i.e. behaviour with RNAV and TACAN CDI, etc. remains the same when tested from Nellis.

[6S.Duke]

Testing with the latest Open Beta 2.9.2.49629 - this doesn't seem fixed i.e. behaviour with RNAV and TACAN CDI, etc. remains the same when tested from Nellis.

I confirm that the fix wasn't included with this patch. It will.be included with the next one

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[shinobi61]

 does this issue persist?

Edited January 30, 2024 by shinobi61

[6S.Duke]

 does this issue persist?

Yes but the fix is coming with the next patch

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