fixed Standby Compass Shows True Heading

[ExA4K]

The standby compass (or wet compass) should show magnetic heading, but it appears to be showing true heading in the F-16.

After alignment, the HSI will show magnetic heading - which should match the standby compass heading (IRL within a degree or 2). The DED INS page shows the True heading, and this matches what the standby compass is showing.

 

 

In the attached image taken while stationary, the mag heading is 300 and the true heading 305 deg and the standby shows a heading of 305.

 

 

[BIGNEWY]

Reported, thank you

[Uwe_21]

I have the same problem. The standby compass shows true heading (true north).

[BIGNEWY]

it is reported, but I have no time line for a fix, it will be addressed during early access. 

 

thanks

[massdriver]

Following the proper alignment procedure for INS, the heading shown in the HUD is always off by approx. -6 degrees if MAGV is set to "AUTO". Only setting MAGV to manual (via LIST->MISC->MAGV->MAN on the DED) with a correction of "E00.0" will make the headings shown on the F10 map correspond with what is shown on the HUD. The "THDG" on the DED during and after INS alignment shows the proper value.

 

Weirdly, this issue only recently appeared. I remember it was working fine a few weeks before.

 

In the attached track, see how the HUD shows a heading of 116 degrees, which must be manually corrected to 122 (the correct heading) via LIST->MISC->MAGV->MAN.

 

Thank you.

MAGV.trk

[ice41]

F10 map and INS DED page shows true heading (hence THDG in the INS page) while the HUD is showing magnetic heading. The numbers should be different according to the magnetic variation.

[massdriver]

Thanks for you response, ice41. I would agree in principle, which is why normally one would use MAGV to correct for that. But in this case, I need to deactivate any MAGV correction to get the heading on the HUD right.

 

In simpler words, in this case, the F10 map, as well as DED, and the HUD all show the true heading (see also how the non-electronic compass on the bottom right of the last screenshot shows 122, the same as THDG in the DED). Because magnetic heading correction is turned on by default (on Caucasus to correct roughly -6 degrees E), it is "over-corrected" and ends up being shown wrong until the MAGV correction is effectively turned off / set to MAN and "E00.0". As all headings on the F10 map are only useful if one can reference to them, e.g. for preparing an ILS approach via TACAN, it seems doubtful whether showing a non-corrected heading in the HUD would be of any use.

 

In simpler words, it appears that Caucasus has no magnetic heading deviation, but the plane corrects for it by default.

[Frederf]

The F-16 cockpit instruments are supposed to show magnetic heading. When you're sitting at parking spot #42 at Kobuleti and facing 122.2° true all the cockpit instruments are supposed to show 115.8° magnetic. By entering a manual MAGV value of 0 into the system you're telling the airplane (falsely) that the magnetic field is aligned with geographic north. The result is that your cockpit instruments display the INS true heading unaltered.

 

There's nothing wrong here.

[massdriver]

Hi Frederf,

 

Thanks for your input. I think you may have missed some of the details I provided though.

 

13 hours ago, Frederf said:

When you're sitting at parking spot #42 at Kobuleti and facing 122.2° true all the cockpit instruments are supposed to show 115.8° magnetic. [...] There's nothing wrong here.

Exactly, please take a look at the annotated screenshot below and the reading on the magnetic compass. There is something wrong, unless magnetic north is supposed to be equal to true/geographic north on the Caucasus map.

 

13 hours ago, Frederf said:

By entering a manual MAGV value of 0 into the system you're telling the airplane (falsely) that the magnetic field is aligned with geographic north.

Under normal circumstances - but this is what I have to do at the moment as a workaround, as the magnetic field is falsely aligned with geographic north in the simulation, or at least on this map. Which is the bug I am reporting.

[ice41]

look like a known issue
 

 

[massdriver]

18 minutes ago, ice41 said:

look like a known issue

 

It is similar, but it is not the same. I am pointing out that most likely the bug is that there is apparently no difference between magnetic and geographic north (at least on the Caucasus map). Which in turn causes the automatic MAGV correction to not work as intended. If you leave it set to AUTO, it over-corrects for a magnetic north deviation that does not exist, thereby making your HUD and other navigation instruments show incorrect (and rather hard-to-use) heading values.

[Frederf]

The magnetic heading of the airplane in the above pictures is 115.8°. Magnetic variation exists in DCS. Every other airplane in DCS which displays magnetic heading will show 115.8° when positioned as the F-16 is in the above screenshots.

 

The whiskey compass showing true is a bug, naturally. The magnetic compass instrument is not showing magnetic heading. While this would be a physical impossibility in real life, due to it being subject to computer programming, such an error is possible in a simulation.

[massdriver]

59 minutes ago, Frederf said:

While this would be a physical impossibility in real life, due to it being subject to computer programming, such an error is possible in a simulation.

Indeed. And nowhere did I claim for such an error to be impossible in a simulation. I was merely reporting a bug.

More precisely, I am reporting two bugs, as described above.

[Frederf]

The only bug present that I see is the standby compass. The HUD showing 116 with default magvar and 122 with zero magvar is correct behavior.

[massdriver]

Interesting. Maybe you can help me wrap my head around the following: assuming you are correct, and the HUD (and HSD) would always show geographic/true north if not "corrected" to show magnetic north via MAGV->AUTO, why would I intentionally skew it to show magnetic north, if all available navigation information (maps, airport charts, runway labels, etc.) is based on geographic north? What utility would it have to always see a heading that you then need to re-adjust in your head to make it usable for navigation?

 

A use case example:

• I am using the autopilot to fly towards an airport with TACAN, to land on runway 06, with geographic heading 64 degrees, following your logic I must set the autopilot to fly to heading 58 degrees to be aligned with the runway. It would seem much easier and practical to simply have the HUD and the HSD work with geographic north to avoid such mental arithmetic.

 

Thanks for taking part in the discussion.

Edited July 17, 2021 by massdriver
Added a sentence to the example

[Frederf]

Historically airplanes had magnetic instruments. That's why ATC gives headings in magnetic. Charts have lots of magnetic. VOR/TACAN radials are in magnetic. Basically all of aviation is set up to reference magnetic north while doing the flying thing. During planning with charts the reference is to the geographical grid. Knowing the relationship between true and magnetic is important to be ready for what magnetic indication on the flight instrument corresponds to the actual true course you wanted to fly. When you got in the airplane in 1931 magnetic direction is all you had.

 

Anyway, the invention of the INS sorta turns that concept on its head. The INS works by sensing the world turning during those few minutes on the ground without regard to the magnetic field. As such it discovers true north all by itself. You're probably wondering why if the F-16 can happily disregard magnetic anything and just work purely in true, why in the world was it designed to show such antiquated reference?

 

The answer is that the F-16 is not the only airplane in the skies. INSs are expensive, like a quarter million dollars. Cessnas aren't going to have that. Everyone has to fly the big friendly skies on a budget and not run into each other. Due to this everyone references magnetic heading while flying because the guy in the $50,000 has a magic rock in a glass bowl. The big boys in $200M 777s can just deal. Plus the magnetic field if well mapped provides a continuous update reference for drift because even INS isn't perfect forever.

 

Yup, a runway with heading 064T will have its runway heading published as 058M on charts. You want to use the exact same ILS approach chart as the guy in the 1955 airplane and the air traffic controller wants to say the same thing to all customers.

 

The USSR VVS for example operates at high latitudes with severe variation and decided that their stuff will reference true north operationally. They have the technology. MiG-21s and L-39s have dials in them set on the ground to nudge their magnetic-sensing navigation systems to show true. USSR controllers are spitting out true headings for interceptions of B-52s. It has been done. VORs and TACANs near the poles will have their radials reference true instead of magnetic. The F-16 and F-18 can switch to true reference as needed because they just might have to do some of that military stuff near Santa Claus's house.

 

DCS is kinda funny because the ILS course on the F10 map is in true which wouldn't be the case on a real chart. Depending on which coalition/faction you are AWACS will give you magnetic or true heading (as well as feet/m height or nm/km distance). It is not consistent with real world (at least USA type) references of heading everywhere. You have to watch out what heading system is being referenced at all times.

[massdriver]

Thanks a lot for these explanations, Frederf! Much appreciated and good to know.

 

I am therefore indeed only reporting one bug, the magnetic compass showing true.