Navigation Drift and general Viggen woes

[Chad Vader]

Hi all.

First, let me say that this module is my favourite module currently in DCS.  I love the playstyle of flying over a target area and dumping enough munitions to destroy a small town, then flying home as fast as possible.  Its kind of like flying a Y Wing during the cold war.  I love the analog nature of the cockpit and the radar and hud display.

Having said that I cant get to grips with the TERNAV system or the Navigation drift and its really pushing me away from the Viggen.  I play online with my friends and they all fly F18's F16's etc and I really need to be efficient in hitting targets or it really ruins the night.

I find that in singleplayer, I'm reasonably accurate, but in multiplayer I cant hit a barn door.

I don't understand how to get the TERNAV to give me a 4 or a 5 when in flight.  Im flying close to the ground over landmarks, mountains and such and i get 1 or a 2 and then drift.  

Could somebody please point me in the direction of how to perform a nav fix?  I cant really see it in the manual and I cant perform it in the jet.  I was told if the ternav showed 4 or 5 it was irrelevant anyway.  My BK 90's are always off, to the left or to the right, always miss, in mp.

Is there an option to disable the nav drift altogether, that would be amazing.  I guess there isn't.  

Don't want this to come off as a whine, it isn't, its just airing some frustrations.

Thanks

[Rudel_chw]

35 minutes ago, Chad Vader said:

Could somebody please point me in the direction of how to perform a nav fix? 

I learned the navigation with this video tutorial … it’s old but should still be current:

 

on multiplayer, this tutorial shows how to add new waypoints to your flight plan:

 

for the bk90 I used to add a navigation fix waypoint using a landmark near the target, to get my navigation right just before weapon release 

[Chad Vader]

Thanks.  Ive seen these and tried the suggestions in game.

I have a drift of 0 and TERNAV constantly gives me 1 or 2, never 4 or 5.  I fly 500ft ish over different terrain.

I fire my BK90 and its always off.

Ill try and upload a track file

[Sideburns]

a) The Ternav works below 500m agl and won't work over water. Are you flying over 500m agl?

b) I believe the Ternav data loaded into the cartridge is around intended waypoints, i.e. stray too far from your intended flightpath and Ternav won't have the data to do it's automatic fixing. Are you setting some waypoints in mission editor or F10 map and then loading cartridge, or manually entering?

c) The Ternav fixing is really nice and automated but accurate to within about 1/2km. If you want really good accuracy you will need to do a manual fix, and it is recommended to do this alongside Ternav, before launching a Bk90 (or refixing your target waypoint). 

For quick guide to visual (overflying) and radar nav fixing, note that you ideally want to pick and set a waypoint over an easily identifiable landmark.

 

Edited March 22, 2022 by Sideburns

[Hobel]

But the Nav Fix is partly not accurate enough for BK90?

I mean if they miss 50-100m the BK90 miss for the most part.

I use the Nav fix as they describe, if I am in the target area, however, I search with the radar my targets and lure them again, this goes with some practice very accurately!

 

What was not mentioned here so far, avoid to pull many G, the more G the higher the possible drift.

[QuiGon]

2 hours ago, Hobel said:

But the Nav Fix is partly not accurate enough for BK90?

The accuracy of the NAV FIX depends on your ability to perform it precisely. If you perform it well, then it is accurate enough for the BK90, but you need to conduct the attack ASAP after the NAV FIX, as the system will start to drift again.

Edited April 16, 2022 by QuiGon

[Hobel]

1 hour ago, QuiGon said:

The accuracy of the NAV FIX depends on your ability to perform it precisely. If you perform it well, then it is accurate enough for the BK90, but you need to conduct the attack ASAP after the NAV FIX, as the system will start to drift again.

Yes well but at 150 - 200 m / s decides but almost rather the coincidence whether I hit the Nav fix under 50m exactly?

[QuiGon]

17 hours ago, Hobel said:

Yes well but at 150 - 200 m / s decides but almost rather the coincidence whether I hit the Nav fix under 50m exactly?

That toally depends on your skill to hit the nav fix accurately.

[Nealius]

Following this since my Bk90s are always missing by 90m or so. What's strange is that only the Mx point has drifted, and after only 6 minutes between wheels up and weapon release. All of my Bx points are fine, with no drift. What would cause the Mx point and only the Mx point to drift?

[Hobel]

vor 2 Stunden schrieb Nealius:

Following this since my Bk90s are always missing by 90m or so. What's strange is that only the Mx point has drifted, and after only 6 minutes between wheels up and weapon release. All of my Bx points are fine, with no drift. What would cause the Mx point and only the Mx point to drift?

Otherwise, do you have a track file of it?   Best not longer than 5-10min

[Nealius]

I have a track file that's under 10 minutes from cold start to weapon impact, but the Viggen replays are broken and I never get off the ground, and have the Torege.....boga....something Swedish Viggen hut structure mod 

[Machalot]

Some shots is the dark then, without seeing your track: 

1. Are you setting the MagVar properly? 

2. Are you waiting until you are on the runway to switch from BER to NAV?

3. Are you aligning precisely to the runway centerline and pressing the Reference button before starting your takeoff roll? 

4. Are you flying below about 300m AGL so you get full TERNAV updates? You should see the last two digits of the CK37 readout as 50 when in AKT POS/OUT.

5. Are you doing any visual nav or radar fixes en route that would move any waypoints? (T1-TV)

6. Are you doing hard maneuvers or rolling more than one revolution? 

7. Are you taking off from the runway designated by your LS waypoint? 

8. Is your Doppler switch in the right position for the surface you're flying over (LAND/SJÖ)?

[Nealius]

1. Possibly not. Since the release in 2017 MagVar has been set properly by default with no need for player adjustment. Has that changed?

2. Yes

3. Yes

4. Yes, although I'm at around 300m for around 30-60 seconds on the attack run

5. No

6. Yes to hard maneuvers, no to rolls. I have the two waypoints along a river and, rather than flying a straight line through the waypoints, I jink through the river between waypoints

7. Yes

8. Yes, set to LAND

Edited August 27, 2022 by Nealius

[Machalot]

41 minutes ago, Nealius said:

1. Possibly not. Since the release in 2017 MagVar has been set properly by default with no need for player adjustment. Has that changed?

Yes, it now has a random offset at every spawn. A wrong setting contributes to nav drift. 

42 minutes ago, Nealius said:

6. Yes to hard maneuvers, no to rolls. I have the two waypoints along a river and, rather than flying a straight line through the waypoints, I jink through the river between waypoints

This might be part of the issue too.  Can you try without the high Gs?

[Nealius]

Ok, two reflies with better accuracy after setting magvar as close as I can to +6.4 and flying straight lines with <3G maneuvers. 

1. Nav Sys warning when I hit the ref button on the runway. I'm guessing I need to manually input the heading. Despite this, TERNAV still shows 0 drift and all Bx and Mx waypoints are accurate to 5~10m. It looks like straight-line nav is best....so much for NOE.

2. With target QFE set Bk90s land long, when I forgot to set target QFE Bk90s were highly accurate. Big question mark here.

Edited August 27, 2022 by Nealius

[Machalot]

8 hours ago, Nealius said:

1. Nav Sys warning when I hit the ref button on the runway. I'm guessing I need to manually input the heading.

This should not happen if your LS information is properly set in the CK37 and you are aligned within 15 deg of a runway centerline.  Are you taking off from an airbase? 

[QuiGon]

@Machalot Hmm, if his alignment or MagVar setting are off, then ALL waypoints should be affected, not just the Mx points.

[Nealius]

1 hour ago, Machalot said:

This should not happen if your LS information is properly set in the CK37 and you are aligned within 15 deg of a runway centerline.  Are you taking off from an airbase?

Road FARP, with LS placed via F10 marker on the section of road I use to take off.

[Machalot]

1 hour ago, QuiGon said:

@Machalot Hmm, if his alignment or MagVar setting are off, then ALL waypoints should be affected, not just the Mx points.

Yeah. I'm trying to hit all the points that might affect nav accuracy generally. I can't account for an observation that M points have error but B points don't. Could be a misperception, but we can't know without a track. I've definitely misperceived what was happening in my bug reports before, and once I got everything else fixed up I saw what was really happening. 

27 minutes ago, Nealius said:

Road FARP, with LS placed via F10 marker on the section of road I use to take off.

For a road takeoff you need to enter the runway heading. It's also very important to do a nav fix before employing BK90s because the nav initialization in a road takeoff has more variance, which affects everything downstream. 

How consistent is your liftoff point in these multiple tests you're running? That affects nav accuracy because your nav state is set equal to the LS point when the wheels lift off.  I wonder if that affected your observation that QFE affects BK90 accuracy, it could have been different liftoff points between the two runs with no nav fix to correct it.

I'm also not completely sure how LS works with road basing and the F10 map. It might accept your LS point from your cartridge, or override your LS point with the location of the FARP in the mission file. Do you know? 

Edited August 27, 2022 by Machalot

[QuiGon]

4 hours ago, Machalot said:

Yeah. I'm trying to hit all the points that might affect nav accuracy generally. I can't account for an observation that M points have error but B points don't. Could be a misperception, but we can't know without a track.

Yeah, a track file would definitely help @Nealius
Without it, it's just guessing in the dark.

[Nealius]

8 hours ago, Machalot said:

How consistent is your liftoff point in these multiple tests you're running? That affects nav accuracy because your nav state is set equal to the LS point when the wheels lift off.  I wonder if that affected your observation that QFE affects BK90 accuracy, it could have been different liftoff points between the two runs with no nav fix to correct it.

Probably not consistent at all, but that would be true if I were flying off a runway as well. I rotate when the HUD indications tell me too but she takes so long to rotate, then suddenly overrotates. At any rate, not lifting off exactly at the LS point at all most likely.

On the run without setting QFE I did a nav fix on B2, target M3. On the run where I did set QFE I did a nav fix on B1, target M3. The distance between B1 and B2 (and then M3) is around 4 minutes, so unless the system is drifting too fast then my nav fix on B1 must have been inaccurate.

It looks like a good chunk of my problem are these nuances between airbases and road FARPs, and changes to things that used to be automatic for many years. 

 

Edited August 28, 2022 by Nealius

[LazyBoot]

9 hours ago, Nealius said:

Road FARP, with LS placed via F10 marker on the section of road I use to take off.

 

8 hours ago, Machalot said:

For a road takeoff you need to enter the runway heading.

I'm also not completely sure how LS works with road basing and the F10 map. It might accept your LS point from your cartridge, or override your LS point with the location of the FARP in the mission file. Do you know? 

 

If placed close enough to the FARP it will work

Also, if using an invisible FARP you can set the "runway" heading by rotating the FARP in the mission editor to the desired heading in order to have it auto-populate.

[Nealius]

I think I've narrowed down my issue but I need a sanity check. I've been doing overfly navfixes with the radar in A1 mode, and the fixes never seemed to do anything. BK90s still missed by a large enough margin to only hit 1/3 of my target area. On a second run, I accidently left my radar in A0 mode when doing the overfly fix, and noticed my waypoints tightened up significantly, and this time the BK90s saturated the target area like they should (despite not setting QFE again).

I'm guessing I was doing my fixes wrong and needed to leave the radar off for proper overfly fixes? The simplified guides I've been using always had the radar on. 

[MYSE1234]

20 minutes ago, Nealius said:

I'm guessing I was doing my fixes wrong and needed to leave the radar off for proper overfly fixes? The simplified guides I've been using always had the radar on. 

Yep, radar has to be off for overfly fixes, otherwise it will make a radar fix. As you've been making radar fixes without moving the radar cursor, that would explain why the fixes aren't doing anything as it's doing a fix at the position it's already at. So zero change in position.

[Nealius]

Welp there's my problem. All sorted now I guess lol.