[BUG] lateral guidance during short approach landing phase 2 without TILS buggy (OB , MT)

[Snappy]

If you perform a short approach flip/flop the lateral guidance you receive seems buggy if you approach the runway centreline at higher intercept angles.  
According to the manual about short approach without TILS :
If the aircraft is outside of the ±20° sector or if the angle of travel is more than 90° relative to the runway heading, a steering command is set towards an approach circle similar to that of the normal phase 1. The approach circle is set 10 km from the touchdown point and is displayed as an angle command on the ADI and HUD. The bearing and distance on the course ring and the distance indicator displays is toward the destination LF.

However this doesn't seem to work at the moment. If you follow the lateral HUD guidance you get along the mentioned circle, you end up not on the extended centreline (as shown on central indicator/calculated by the nav system ) but on a parallel course left or right of it. Something like this:

The lateral offset is significant in its size. And its not the nav systems accumulated error that causes it, because your central indicator looks something like this after you follow the lateral guidance through and roll out on final approach course  : 

 

 

So you can see, even the nav systems own calculation of where the destination airport  and extended centreline are shows it to be quite off to one side of you, in other words the nav system should have been capable of accurate lateral guidance.

The yellow commanded course of the CI points to the destination airport itself, but the HUD lateral guidance is decoupled from that and guides you onto the false parallel of the extended centreline. If you keep following the HUD lateral guidance sometimes it later corrects itself and leads to the approach course, but by then you are much closer to the airfield and have to make large corrections.

With TILS use ,it gets somewhat better, but even then, until steady TILS signal is received it often guides you significantly offset to one side and then with the TILS signal is suddenly realizes that and you get a big correction guidance, which results in large heading corrections you have to make until you are established on final approach.

 

I`m unsure in how far this is related to my other bug report here, where the nav system incorrectly takes LB1 instead of LF1 as the current destination waypoint during Phase 2 , or whether this is a separate bug.

 

 

Regards,

Snappy

 

Edited May 6, 2023 by Snappy

[TOViper]

Hey Snappy!

I might find a minute very late in the night to test it. Two questions:

a) On which runway did you land on?
b) I assume you flew by hand, not using AP, right?

 

Edited May 6, 2023 by TOViper

[Snappy]

48 minutes ago, TOViper said:

Hey Snappy!

I might find a minute very late in the night to test it. Two questions:

a) On which runway did you land on?
b) I assume you flew by hand, not using AP, right?

 

 

Hi Toviper,

I tested this with different airports in Caucasus Theatre.

I tried both , manual flight and with autopilot, though I don’t think it should make a difference as long as you manage to accurately follow the HUD lateral guidance and keep it centered in the FPV during the entire approach.

If you test it, best pick an intercept angle of 90 degrees or so to the final approach course
like the red in my illustration picture and without using TILS.

Edited May 6, 2023 by Snappy

[TOViper]

copy, did you test this in ST as well?

[TOViper]

I wasnt't able to reproduce in MT version. See track.
Maybe you can provide a track from MT version?

 

2023-05-06_AJS37_LANDN-NAV_PO_LANDN-NAV.trk

Edited May 6, 2023 by TOViper

[Snappy]

11 minutes ago, TOViper said:

I wasnt't able to reproduce in ST version. See track.
Maybe you can provide a track from MT version?

2023-05-06_AJS37_LANDN-NAV_PO_LANDN-NAV.trk 308.84 kB · 0 downloads

Hi Viper, this is a track I just made on the MT version.  In the beginning I turn left and fly on that heading just to produce a higher intercept angle. The track shows once you enter the approach circle , the HUD lateral cues lead too far left , parallel to the centreline on the Central indicator. At the end of the track the guidance catches on and jumps to right, but by then you are already off. 

Hope it plays out ok on your end. I attached the mission file too, should you need it for the track, its from the Viggen training mission in the user file base.

ViggenFlipFlopLateral.trk M06 - Landing - Clear Sky.miz

[TOViper]

Copy, thanks, I will take a look in the late evening.

[Snappy]

12 minutes ago, TOViper said:

Copy, thanks, I will take a look in the late evening.

Hi, thanks alot . Yes its interesting , when I play your track I can see it works on your side. I made a new track, just slightly more accurate flying, but same result, the guidance leads to a parallel left of centreline . In the very end the guidance jumps to the right again to correct.

 

ViggenFlipFlopLateral2.trk

P.S.: I also experienced this issue, while reflying the the mjolnir response&wrath of thunder campaigns, so its not the specific mission file nor the airport .

Edited May 6, 2023 by Snappy

[TOViper]

Hm. Are you sure you set the correct BANA GRÄNS for the runway (e.g. 07 for Kutaisi) when landing from WEST to EAST?

[Snappy]

5 minutes ago, TOViper said:

Hm. Are you sure you set the correct BANA GRÄNS for the runway (e.g. 07 for Kutaisi) when landing from WEST to EAST?

You mean the landing runway direction? yes, otherwise, the line extending from airport circle would point away from me during final approach. But I checked again. The correct runway direction is selected.

Edited May 6, 2023 by Snappy

[TOViper]

Hm. I would start over with suggesting you a DCS repair...
Why I suggest this? Very simple: After an OB Update in the past (about 2 years ago, I made a post), I had a mixture of older and new files of F-14 on my disc, which produced funny behavior. The repair did the job ... and I was happy again.
 

[Snappy]

45 minutes ago, TOViper said:

Hm. I would start over with suggesting you a DCS repair...
Why I suggest this? Very simple: After an OB Update in the past (about 2 years ago, I made a post), I had a mixture of older and new files of F-14 on my disc, which produced funny behavior. The repair did the job ... and I was happy again.
 

Hmm might be a good idea I guess. Do you know by chance if that will reset all graphic&other DCS settings and campaign progress?

[TOViper]

It doesn't, since it only checks the files in the DCS installation folder, not in the DCS Saved Games folder.

[Snappy]

ok, great, I ll try that then. Hopefully that fixes it. Thanks for the tip Viper!

[Snappy]

@TOViper Hmm, not good. I ran the full/slow repair and I still see that behaviour. Really dont know what causes this..   Its annoying. If you see anything wrong in my track, please let me know

[TOViper]

I watched the track several times now, and I think I am now aware of what is happening.

Even if following what is written in the book on page 158, the HUD guidance is not working as I would expect; ADI and HUD diverge, and HUD is "glued" to the currently flow heading.
@QuiGon, may you take a look plz.

Note: In the mission the TILS is not turned off (or set to a wrong channel), it has to be done after hopping into the aircraft.
I have done two flights, one with the original mission, and another one with my own mission (_2.trk).

References: page 151, 152, 158

2023-05-07_AJS37_LANDN-NAV_PO_LANDN-NAV_bad_HUD_guidance.trk

2023-05-07_AJS37_LANDN-NAV_PO_LANDN-NAV_bad_HUD_guidance_2.trk

Edited May 7, 2023 by TOViper

[Snappy]

14 hours ago, TOViper said:

I watched the track several times now, and I think I am now aware of what is happening.

Even if following what is written in the book on page 158, the HUD guidance is not working as I would expect; ADI and HUD diverge, and HUD is "glued" to the currently flow heading.
@QuiGon, may you take a look plz.

Note: In the mission the TILS is not turned off (or set to a wrong channel), it has to be done after hopping into the aircraft.
I have done two flights, one with the original mission, and another one with my own mission (_2.trk).

References: page 151, 152, 158

2023-05-07_AJS37_LANDN-NAV_PO_LANDN-NAV_bad_HUD_guidance.trk 213.16 kB · 0 downloads

2023-05-07_AJS37_LANDN-NAV_PO_LANDN-NAV_bad_HUD_guidance_2.trk 170.93 kB · 0 downloads

 

Viper, does that mean, you were able to reproduce the issue?

Edited May 7, 2023 by Snappy

[TOViper]

If we talk about landing WITHOUT TILS in use, I think that the HUD indications during the 2nd phase (page 151) are not correct. The book says:

"Phase 2, TILS not in use
All the navigation indications are based on the navigation systems estimation of the aircraft position. The course indicator bug on the course ring indicates the heading towards the touchdown point LF. On the CI, the circle marker indicates the touchdown point.
>PICTURE<
Steering command along the circumference of the approach circle is displayed on the ADI and the HUD in the following manner. If the aircraft angle of travel after passing LB diverges more than 5° from the extended runway centerline, the pole track and reticule in the HUD move to correspond to a bank angle yielding a 4,100 m turn radius."

This is not what's happening in the sim.

What happens is that the HUD indication "sticks" to the currently flown heading, and turns with the turning aircraft. So if you follow the HUD only, you end up somewhere, but not aligned with the runway. If you follow the CI, you would never notice that the HUD is not leading, since it simply follows your steering.
This issue relates to normal (long) approaches AS WELL AS shortened approaches, both WITHOUT TILS and ST+MT version.

This is wrong behaviour I strongly assume.

If @Machalot or @MYSE1234 are around, they are welcome to comment too. Any other drivers too of course ...

Edited May 7, 2023 by TOViper
additional information

[Snappy]

50 minutes ago, TOViper said:

If we talk about landing WITHOUT TILS in use, I think that the HUD indications during the 2nd phase (page 151) are not correct. The book says:

"Phase 2, TILS not in use
All the navigation indications are based on the navigation systems estimation of the aircraft position. The course indicator bug on the course ring indicates the heading towards the touchdown point LF. On the CI, the circle marker indicates the touchdown point.
>PICTURE<
Steering command along the circumference of the approach circle is displayed on the ADI and the HUD in the following manner. If the aircraft angle of travel after passing LB diverges more than 5° from the extended runway centerline, the pole track and reticule in the HUD move to correspond to a bank angle yielding a 4,100 m turn radius."

This is not what's happening. What happens is that the HUD indication sticks to the currently flown heading, and turns with the turning aircraft (if flown so). So if you follow the HUD only, you end up somewhere, but not aligned with the runway.
This is wrong behaviour I think.

But I will double check with my fellow mate Quigon this evening. I want to hear what he has to say, since he is also an old and experience DCS Viggendriver ... .
If @Machalot or @MYSE1234 are around, they are welcome to comment too. Any other drivers too of course ...

 

Hmm I'm not sure I understand. What was the difference to the first track you posted yesterday, where it seemed to work ok?

[TOViper]

Yesterday I followed the CI, not the HUD
When you follow the CI, you will never notice that the HUD guides you wrong, because the HUD follows your turns instead of leading you.

You can try it out: Emphasize on the phase 2, and fly turns within this phase.
You will notice that the HUD follows you, instead of the HUD leading you to the correct heading.
Don't forget to turn OFF the TILS by rotating to a channel different from that of the runway.

Edited May 7, 2023 by TOViper

[Snappy]

9 minutes ago, TOViper said:

Yesterday I followed the CI, not the HUD
When you follow the CI, you will never notice that the HUD guides you wrong, because the HUD follows your turns instead of leading you.

Ah, now I get it. OK, I was talking about the HUD guidance the entire time when I wrote "lateral guidance".  I also noticed the HUD guidance and course index pointer on the CI seem decoupled during approach, but I do not know whether that is correct or not behaviour . I think it is, since the destination Waypoint should become LF, i.e. the touchdown point during Phase 2 , but the HUD should guide you to the extended centreline.

I just assumed the HUD was meant to be the primary guidance during approach, since its supposed to lead you onto the extended centreline.

In any case the HUD guidance seems to be the actual problem, since it does not guide you where the manual says it does. 

Edited May 7, 2023 by Snappy

[TOViper]

yup

[Snappy]

1 minute ago, TOViper said:

yup

I edited my reply  above yours for additional input.

[TOViper]

I added some more infos on my post above for the devs.

[Silhou]

Hey! Thanks a lot, @Snappyand @TOViper.

Tracked as AJS37-357.