[REPORTED] Hornet Command Steering Bug and Mag Variation - Tracks Provided

[Mikaa]

Apologies if this is already reported or known by devs, but I searched for keywords couldn't find anything specific to this (although I suspect many other wind related issues for autopilot HDG etc. stem directly from this one). I believe I've found the source of all of these nav problems with with Command Steering Cue and the HUD/HSI applying the Magnetic Variation Twice. This was really annoying me, so I took the time today to figure out what's going on.

 

A few Assumptions before we begin:

-Auto Throttle and BALT are used to ensure the only flying variable is HDG control

 

- FA-18C onboard variation of ~6.45-6.5 degrees is correct (6 degrees 27', or 6 degrees 31' on HSI A/C Data Page)

 

- The Waypoints set up for the test equate to 180 Degrees True - Assuming the mission editor Lat/Long are correct, WP0 is (N43,00',00"/E41,45',00"), and WP1 is (N42,15',00"/E41,45',00"), thus it should be 180 Degrees True Track.

 

- Oil Rigs are placed along this track at various latitudes to give visual representation to ideal track

 

- Wind in Mission Editor was set to "To" 264 Degrees Mag, which is "From" 084 Degrees M, or ~090 Degrees True, at 50 kts - Perpendicular to our flightpath

 

- TAS of 496 kts is used at 22,000' (350kts CAS) to ensure uniform wind correction throughout

 

- The above was calculated using standard ISA 29.92"Hg, 15 Degrees C, and an assumed density ratio of .498 at 22,000', equating to CAS 350, TAS 496, and GS 496-497, negligible increase, so TAS is assumed equal to GS.

 

From the above, I independently calculated the various Courses and Headings required via E6B (MB-4A) to test the ingame command steering:

 

TC=180

TH=174

MC=~173.5-174

MH=~167.5-168

 

Okay, with all that out of the way, here we go...

 

Track 1 - Mag Error:

This track shows that assuming the variation, and a WCA of -6 degrees East, the CORRECT Command Steering Cue for a heading of 167.5-168 Mag. HOWEVER, if this is flown via the Command Heading Steering Pointer lined up with the HDG Caret (as is prescribed in NFM-000 24.2.9.1), both the HSI, and HUD do not correspond to the required track, and we end up drifting. Looking at the HSI, we can see the drift error shows us flying approx 174 degrees. We'll come back to why this is...

 

Track 2 - True Error:

I actually flew this track first, but figured it would be better ordered like this in the report. Same setup as before, and the same correct Command Heading Steering Pointer of 167.5-168 is shown for correct Mag HDG. In the Data, A/C page, I then select True Heading. Again, the correct TH of 174 degrees is shown is displayed... but, I then fly the previous Mag HDG of 167.5 degrees, and you can see the correct track is followed all the way to WP1...

 

Whats happening???

 

I believe the magnetic variation is being applied twice. Once, to the Command Heading Steering Pointer, and then the entire Heading tape and HSI is rotated an additional magnitude of the variation, so in Mag HDG Mode we're off by 13 degrees, and in True HDG Mode, we're off by 6.5 degrees.

 

Track 3 - No Wind:

Third track is identical to the first two, except now the wind is eliminated, meaning a MC and MH are identical, and TC and TH should also match. Variation is the only, well, variable. It initially is commanding ~167.5-168 Magnetic to WP1, which is NOT correct, but coincidentally, exactly double our variation. Switching to True Heading mode, the Tape shifts, and now we're commanded approx. 6-6.5 degrees from our known TC/TH of 180. You can see the oil rigs are perfectly lined up along this track, and in "True Mode" flying this Commanded "variation" gives us a proper track across the ground to WP1 (which it totally shouldn't).

 

In Summary:

It seems that Mag HDG mode has both the HSI and HUD tapes applying Mag Variation Twice - Once properly for the Command Cue, and then again, shifting the entire tape clockwise, doubling the effect. When wind is applied, the HUD steering cue is correct in relation to the heading tape it sits on, but the entire tape should be shifted counterclockwise the same magnitude of the variation in order for the Command Cue and HUD Caret (and im also thinking velocity vector) to line up properly for Navigation. When there's no wind, the HUD tape and HSI just needs to be rotated (again by the magnitude of the variation, or ~6.5 degrees CCW) so that MC=MH and TC=TH.

 

A few closing notes: As I was writing this up, I noticed that Map North seems to be in relation to Magnetic, because the variation between the mission editor plotted track of 180T, and Map South are different by ~6 degrees East. Im betting that this is part of the culprit that's applying the variation a second time to the HUD HDG Tape and HSI. I also used the Caucasus map because the variation is ~6 degrees, vs (I think) 2-3 in PG, so any issues would be much easier to spot. I may test the other maps when I get the chance.

 

I'd love some feedback from you guys.

FA-18C Command Steering Mag HDG Error.trk

FA-18C Command Steering True HDG Error.trk

FA-18C Command Steering Error No Wind.trk

[Robin_Hood]

You got a problem right here:

 

- The Waypoints set up for the test equate to 180 Degrees True - Assuming the mission editor Lat/Long are correct, WP0 is (N43,00',00"/E41,45',00"), and WP1 is (N42,15',00"/E41,45',00"), thus it should be 180 Degrees True Track.

 

Because of how DCS World is currently modeled, those two waypoints will usually not be placed along a true north-south alignment. "True north" in DCS is what you would normally call "Grid north", ie. straight up on the map, and magnetic headings are based upon this (plus the magnetic variation). All aircraft instruments use these two. Actual true north is not normally used in DCS.

 

So I know it sounds like a complete contradiction, but in DCS, True north does not follow constant longitude lines. Here's a little picture to explain what is happening in DCS.

Hopefully someday an actual spherical world model can be used, but for now we have to make do with this (one thing it messes up is if you are doing calculations on coordinates).

[Mikaa]

I figured as much (see the bottom of my first post). So we're dealing with a conic/stereographic projection of some type. Oof. This means that every aircraft is affected, and as soon as any wind is applied, all navigation goes out the window because the supposed headings to fly don't account for the difference between True North and Grid North.

 

Now for something simple like the F-5, although less than ideal, we can just apply an additional correction when flying off the compass (in the case of Eastern Caucasus, just subtract an additional 6 degrees from the wind corrected Mag HDG).

 

Funny thing is, the way the aircraft are coded (I checked this in the F-5), it thinks that True North IS Grid North, because when I loaded the exact same mission and winds in the F-5, it pre-selected a HDG Bug of 167ish (which is the correct wind adjusted HDG to fly relative to Mag North). But like in the F-18, you won't get where you want to if you fly that because of the Grid displacement.

 

Now the problem with advanced aircraft that rely on INS Position, and have very complex nav systems coded to great detail (i.e. F-18 and F-16), is the wind corrections are applied thinking that True North = Grid North... so it's completely useless to even look at the HUD cues. Although they seem correct, none of the numbers or guidance on the HSI or HUD corresponds to what you see outside the cockpit. I tested the exact same mission in the F-16, and sure enough, the Tadpole does the same thing - Shows the correct wind adjusted track to fly, relative to True North, so we're off course by exactly the delta from True to Grid.

[Mikaa]

Update:

 

I just checked the other maps to determine their Grid vs True North Errors. Perfectly acceptable at <1-2 degrees, sometimes as high as 3 on the edges of the map. That lies within the margin for error in piloting skill - absolutely no issues with this. And I totally understand from a development point of view that the Caucasus map is old, and free, but that really sucks that none of the basic nav functions work properly there for any mag instruments if wind is present, and the only way to navigate to anything on the ground dead reckoning style is without wind and via Grid HDGs.

 

So using the PG map, which has a variation of 2 degrees, I set up a similar test, but this time, there is negligible difference between Grid and True, so we should get pretty accurate HUD Command Heading Steering for both Mag, and at the very least, True HDG mode right?

 

Nope.

 

There is absolutely no wind correction applied to either the F-18's HUD Command Cues, or the F-16 Tadpole in the PG map. Ironically, without an appreciable Grid vs True error in the PG map, the Hornet's HSI wind drift barb is actually correct here, in both Mag and True mode, just not the HUD.

 

I then went to the Nevada Map, where the variation is 12.7 degrees. Similarly negligible Grid error (about a degree near most of the airports), and it's the exact same problem as PG. Zero wind correction is applied for both the Hornet and Viper. I then checked Normandy... same as PG and Nevada.

 

So the default free map has a grid error relative to nav instruments, but correctly applied wind drift to the HUD cues... The actual paid DLC maps have a barely significant grid error, but no accounting for wind drift in the HUD...

 

What is happening??

 

I'm going to just chalk all this up to Early Access, and assume it's being worked on, but I'd love someone who knows better to hop in and provide some insights, and whether this is going to be fixed. As it stands, effective nav using the HUD Cues is impossible.

Edited January 22, 2020 by Mikaa
a word

[NineLine]

The options to set the wind correctly is a reported bug, I believe the info is the same every time you enter the Hornet, no matter what, it affects CCIP, which is what was reported for it, so I would assume this is along those same lines.

[KlarSnow]

The INS in the F-18/F-16, anything with an INS should be getting the wind correction for its current altitude on its own.

It knows the aircrafts heading, Groundspeed vs True Airspeed, and Course. Any difference in ground v true or heading v course equals wind at the aircrafts current altitude.

 

It should be automatically taking that into account with any navigation or bombing mode, without any entry or selection by the pilot.

[NineLine]

Yeah, none of that is currently working and is all reported, the fact you can't enter it, nor is it set automagically. Right now, anytime you are in the Hornet, in the HSI it says 0 wind speed and 45 degrees for direction.

[Santi871]

The INS in the F-18/F-16, anything with an INS should be getting the wind correction for its current altitude on its own.

It knows the aircrafts heading, Groundspeed vs True Airspeed, and Course. Any difference in ground v true or heading v course equals wind at the aircrafts current altitude.

 

It should be automatically taking that into account with any navigation or bombing mode, without any entry or selection by the pilot.

 

There's supposed to be a WIND option in the stores page on the bottom row for conventional bombing calculations, but I'm not exactly sure what selecting it does - to be precise I don't know if it overwrites the current calculation with stored wind data or whether it enables wind to be factored in at all, or something else. Maybe ED can dig into it.

[Mikaa]

Thanks for flagging this. Between the Grid discrepancies and inconsistent wind steering cues, I was getting thoroughly confused.

[KlarSnow]

There is usually a way to enter in a wind table, so if you are dropping from 20,000 feet, and you have a product which tells you the local area winds, you can then enter in the winds at various steps below you, that way it can be more accurate. It "should" always correct for the current winds that are affecting the aircraft, and then extrapolate that down to ground level somehow. Obviously entering the winds for various levels below you will make it more accurate.

 

Some aircraft (F-15E) can capture winds into the table as it climbs, so for example in a pop up attack it would capture the winds in the climb up, and then use those for the release if you have it setup that way. Don't know if the hornet does that, but its plausible.

[NineLine]

There's supposed to be a WIND option in the stores page on the bottom row for conventional bombing calculations, but I'm not exactly sure what selecting it does - to be precise I don't know if it overwrites the current calculation with stored wind data or whether it enables wind to be factored in at all, or something else. Maybe ED can dig into it.

 

It's in the pipeline, just not sure where right now.

[KlarSnow]

Any updates on wind corrected steering cues. The ASL and VV are correctly wind corrected, but the HSI Steering cues, nor the HUD steering caret in either A/G or nav modes is wind corrected.

 

Basically this is how it is currently, and is wrong.

 

 

This is what it should look like

 

 

This is a minor but glaringly obvious thing that should be handled by the INS just like the ASL and the VV. Yes there should also be a way to enter and view the wind effects on the aircraft, but the INS is already compensating for it based on "detected wind." It should be a quick fix to update the cues in the HUD/HSI to match, and then save the manual entry/display stuff for later.

Edited October 4, 2020 by KlarSnow

[hein22]

The options to set the wind correctly is a reported bug, I believe the info is the same every time you enter the Hornet, no matter what, it affects CCIP, which is what was reported for it, so I would assume this is along those same lines.

 

I don't understand this statement. What is "the optiones to set wind correctly"? What is it that is not working (apart from the steering wind corrected cues)? Thanks

[Santi871]

I don't understand this statement. What is "the optiones to set wind correctly"? What is it that is not working (apart from the steering wind corrected cues)? Thanks

There should be a WIND option in the stores page which shows a wind table to manually enter winds for bombing calculations. I was mistaken to bring it up in this thread though, wind tables for bombing are unrelated. It's also possible to manually override the wind calculated by the INS IIRC.

 

Steering cues being wind corrected like klarsnow said is something absolutely basic and it needs to be addressed. The INS is already "aware" of wind because of the velocity vector on the HUD and things like the heading vs track in the HSI. So correcting the steering cues to account for it shouldn't be a problem.

Edited October 5, 2020 by Santi871

[hein22]

There should be a WIND option in the stores page which shows a wind table to manually enter winds for bombing calculations. I was mistaken to bring it up in this thread though, wind tables for bombing are unrelated. It's also possible to manually override the wind calculated by the INS IIRC.

 

Steering cues being wind corrected like klarsnow said is something absolutely basic and it needs to be addressed. The INS is already "aware" of wind because of the velocity vector on the HUD and things like the heading vs track in the HSI. So correcting the steering cues to account for it shouldn't be a problem.

 

But what about the question I asked? What did Nineline mean by his statement? It sounded like the wind window in the ME is bugged, which I didn't know.