Small bug in Terrain Avoidance Mode

[Holton181]

So, finally!

At last I found out how to make the Terrain Avoidance Mode (TAM) actually show anything useful!

It was due to a small bug and rather sensitive antenna elevation adjustments with only buttons (no axis exist for it what I know, pleas add) I could never make the TAM work as advertised in the manual. The manual states

"Has a middle “snap” position"

regarding the Antenna elevation potentiometer, p 115, and further on regarding TAM on p 117 it says

"On engaging the mode, the radar antenna will be set to 0° relative to the horizon (assuming the antenna altitude potentiometer is set to the middle position)..."

I have always assumed "the middle position" imply the "middle “snap” position", and likewise the original position of the potentiometer at startup. But when the potentiometer is at that position, the radar in TAM show almost nothing regardless of terrain in front of you. I have earlier played around with the elevation slightly, but due to its sensitivity (and lack of axis control) it has been difficult to find that exact position giving you a good representation of the terrain straight forward. Even more difficult, not to say impossible, to actually trust it being really straight forward. When having AKAN one can see that elevation indicator above the radar screen. With the potentiometer in its original position the vertical indicator dash is not located in the middle as one could maybe expect, but on the right end of the middle horizontal dash. I have no clue if this is a correct representation in relation to the real thing. When adjusting the elevation, it appears to be a detent at that position though (with an axis control [highly desirable] that detent would not be desirable due to how game controllers are generally constructed and the lack of authentic potentiometers).

 

So I put together a series of screen shots in AKAN mode, with the radar potentiometer in its original position and with the elevation marker at the middle of that horizontal dash (a little tricky to get it there, did I mention the lack of axis control?). I had the radar in LOG and in both PPI and B-scope, with and without TAM:

Ocular View

PPI original elevation

PPI original elevation in TAM

B-scope original elevation

B-scope original elevation in TAM

PPI adjusted elevation

PPI adjusted elevation in TAM

B-scope adjusted elevation

B-scope adjusted elevation in TAM

 

 

To me it looks like either (1) the antenna position when going to TAM at original potentiometer position is wrong, not 0° as stated, or (2) the original potentiometer position with associated detent isn't at all the middle position, as also stated, but the TAM elevation is related to it anyhow. Or the manual is wrong (3)?

I vote for (2), without actually knowing.

I attached the miz file used for the screen shots, starts with active pause at the exact location for my shooting session, for anyone who like to reproduce.

 

 

EDIT:

Yes, I'm on 2.5.3.24984 OB

AJS37 Terrain Avoidance Mode.miz

Edited December 8, 2018 by Holton181

[QuiGon]

Very good testing. I was wondering about this for quite some time, but never bothered investigating it. So thanks a lot for doing that! I hope the devs will respond to explain why it is like that.

[corvinus]

I've tried your mission and I observe the same behavior. But ... in my own terrain avoidance mission I see different behavior, the TAM seems to work fine. I did find out the following:

 

• Fly level.
  
• Turn on the PPI (A1).
  
• Enable TAM.
  
• Wait a few scans.
  
• Switch to AKAN JAKT on the weapon selector.
  
• Wait a few scans.
  
• Switch out of AKAN JAKT.
  

 

So, what happened? When you switch to AKAN JAKT the antenna elevation changed and the PPI went a solid light green, i.e. almost no returns. If you switch out of AKAN JAKT, the PPI showed returns of hill sides again.

 

It seems that switching to AKAN JAKT changes the antenna elevation (I think this is how it should be). So this might interfere with your findings, wouldn't it?

 

You could try a different mission, I have tried the terrain avoidance mission from:

https://www.digitalcombatsimulator.com/en/files/3302241/

(2 Navigation - M04 Terrain Avoidance)

 

 

P.S.: I have also observed some quirky behavior with active pause. Often, if I go out of active pause the Viggen violently pitches up. Some I wonder if the internal Viggens attitude corresponds to the way the Viggen is displayed on the screen. This could be a thing ...

[Holton181]

...

Thanks for this corvinus!

As a matter of fact, I played your highway landing mission in the Viggen training package yesterday night, and I experienced something fitting your findings.

While positioning myself for the landing flying low over the nearby hills, I turned on PPI and then TAM. To my surprise I got good returns of the hillsides in front of me (without touching anything else). To see if the angle was different than in my own missions I turned TAM off and swished to AKAN, but the indicator was at the same original position. Turned TAM back on, and now it was basically all empty. I didn't try to leave AKAN mode, I didn't know that mode are supposed to change the elevation. It was late so I went to bed and planned to investigate further when time permits. But you beat me to it. I will try my own mission again with this in mind.

 

But now a few questions arised:

How do we know the radar elevation if the indicator only appears while in a weapon mode that changes the elevation?

More important, how do we know we have it in its default setting if we have done some adjustments before?

Since we don't have an authentic potentiometer with a detent at the correct position, are we forced to turn to AKAN mode, adjust the elevation back to default (for AKAN) and then turn back whatever weapon mode we had?

Quite tedious and not very user friendly if one like to switch back and forth between a ordinary radar with adjusted elevation and TAM (maybe not how one should use it in the first place, but still).

Also, if it is a correct behavior of the elevation to change when turning to say AKAN, it needs to be mentioned in the manual. Maybe it is somewhere already (haven't read it completely yet to be honest), but it is not in the section about the TAM.

[Jediteo]

The elevation issues are on the internal radar to-do list.

[Holton181]

The elevation issues are on the internal radar to-do list.

Excellent! Thanks.

Would it be possible to add a elevation resett button to quickly return the elevation to default?

This would not work if an elevation axis was added and assigned though.

[corvinus]

The elevation issues are on the internal radar to-do list.

Good to know, thank for letting us know!

[QuiGon]

The elevation issues are on the internal radar to-do list.

That's good news, thanks! :thumbup:

[Holton181]

I would like to add some pictures if it might help the team. They are taken from the same mission above, except I increased the altitude from 100m AGL to 200m AGL. In all pictures I have increased the gain to max using keyboard (no axis assigned), range is 15km, TAM is on.

 

Elevation untouched, weapon mode SJÖ

Elevation untouched, weapon mode AKAN

Elevation adjusted as above, weapon mode AKAN

 

Everything is consistent in the sense going back and forth between these settings always generates the same images. But what I find interesting is the difference between untouched/SJÖ and adjusted/AKAN. I would expect them to be the same basically. They look quite different, and adjusting the elevation in untouched/SJÖ down moves the "radar return arc" closer (quite expected) and up while in SJÖ makes the image go blank. No way to make untouched/SJÖ to look similar to adjusted/AKAN. BUT, by adjusting the elevation slightly further down in AKAN one can make it look similar to untouched/SJÖ. Not consistent here.

 

Any how, I look forward to whatever the team decides to do about it.