RP-22 sma Sapphir Radar bug with 1.5.3 update 1

[fjacobsen]

With the latest update I find that finding targets with the RP-22sma Sapphir Radar has become much more difficult.

 

I have setup some tests, which makes me conclude that the Radar Dish no longer is stabilised in pitch (and maybe also not in roll)

 

Stablisation is, according to various sources, ±40° in pitch and ± in roll.

 

The scans vertically between ÷1.7° - +17° - this should be relative to the horizon.

 

But what I see is that this now is relative to the Aircraft direction, which is dependent on angle of attack.

 

So flying with an AOA of +4°, the radar is actually not looking 1.7° down, but: ÷1.7 + 4.0 = 2.3° up.

 

This means that inorder to track a target at a range of 30 km, You must be 1500 m below the target. Being sligtly below or at the exact same altitude puts Your target below the radar scan zone - all depending on Your AOA.

 

For a radar that has been reported to be gyrostabilised, this doesn´t look right.

 

 

FinnJ

[lukark]

Same problems with radar and olso with pipper on ground targets.

[Cobra847]

We are aware of this issue and a fix should be available shortly.

[fjacobsen]

Thank You Cobra.

 

The Mig-21 is still awsome and one of my favorite aircraft in DCS :)

 

FinnJ

[Tarres]

The RP-22 scans in the following elevation patterns:

 

0º to +17º: standard pattern

+1.5º to +17º: low altitude mode

[fjacobsen]

The RP-22 scans in the following elevation patterns:

 

0º to +17º: standard pattern

+1.5º to +17º: low altitude mode

 

As far as I know its ÷1.7 - 17° standard pattern

Which casn me raised by 1.5° in low alt mode.

 

But still its should be stabilised in both roll and pitch, thus the 0° radsar line is relative to the horizon and not aircraft horizontal reference i.e pitch attitude.

 

But Cobra has allready confirmed this issue as pointed out in his post above.

 

FinnJ

[Tarres]

The -1.7º it´s for the "beam mode", fixed in azimuth and -1.7º in elevation.

 

According to various manuals, the RP-22 antenna is fixed, not stabilized to the horizon.

 

Standard operation manual indicates that the intercept course must be 1000-1500 meters below the target altitude, due to the scan cone of 0º to 17.5º.

 

Of course I could be wrong.

[Cobra847]

We have gone over the radar stablisiation in another thread/post. They are correct.

There is currently a radar bug with both stabilisiation and detection of targets.

 

Since we were at it; we've improved our radar detection algorithm.

[zaelu]

The -1.7º it´s for the "beam mode", fixed in azimuth and -1.7º in elevation.

 

According to various manuals, the RP-22 antenna is fixed, not stabilized to the horizon.

 

Standard operation manual indicates that the intercept course must be 1000-1500 meters below the target altitude, due to the scan cone of 0º to 17.5º.

 

Of course I could be wrong.

 

What is the correlation between the existent bug confirmed by Cobra and your info? It seems like you are saying there is no bug although Cobra confirmed it and they are working on it.

[fjacobsen]

I have read further info the radar. Most info is from the RP-21 though.

mainly here: http://www.mig-21-online.de/

But also from a reallife Mig-21 manual.

 

I´m not sure how the stabilization should work, but common description tells that in search mode the radar will search ±30° on azimuth and ±12° in pitch (though the pitch values are differently described by various sources).

 

The search line is depressed by 3° inorder to compensate for average aircraft pitch relative to the horizon due to AOA. This 3° is further adjusted slightly up or down depending on which type of missile is selected.

 

The indication for whether the target aircraft is above, below is NOT relative to aircraft altitude, but relative to where the nose is pointed i.e sightline.

 

So it seems that current implementation isn't far from reality.

 

FinnJ

[zaelu]

Since we are at it, is the Mig21 radar scanning in rows like Mirage radar? Or much simpler/weaker(?) one line?

[fjacobsen]

Since we are at it, is the Mig21 radar scanning in rows like Mirage radar? Or much simpler/weaker(?) one line?

 

As far as I have uderstood the scanpattern works quite differently in the Mig, but covers what could be regarded as 3 bars.

 

(Try to draw the below pattern):

It starts at the left (30°) mid (0°) position.

Then moves to right (30°) mid (0°) position.

Then to right (30°) low (8° declined) position.

Then to left (30°) low (8° declined) position.

Then to left (30°) high (8° inclined) position.

Then to right (30°) high (8° inclined) position.

Then to right (30°) mid (0°) position.

Then to left (30°) mid (0°) position.

Then to left (30°) low (8° declined) position.

Then to right (30°) low (8° declined) position.

Then to right (30°) high (8° inclined) position.

Then to left (30°) high (8° inclined) position.

Then to left (30°) mid (0°) position.

Then starts over....

 

The radar beam is a baseballbat shaped signal with the thick end at the far away position.

This beam is 4,8° and rotates exentric to form a 9° beam inorder to have a "signal even zone".

By the movement between mid, low and high angle (±8°) the beam covers 9/2 (roughly half the beam) + 8 + 8 + 9/2 (roughly half the beam) = 25° (effective only 24° due to the rotating beam form).

 

All this is declined by 3° to compensate for the normal aircraft pitch attitude.

 

This pattern is stabilised between ±70° in roll, but not stabilised in pitch, thus as the descriptions I have tell - the search pattern will follow pitch movement and the "target below", "target inline" and target above" indications are not relative to altitude, but to the Mig's longitudal axis.

 

Look here (in German):

http://www.mig-21-online.de/

Under: Mig-21 "Fishbed" -> Flugzeugsysteme -> Funkmessvisier

 

FinnJ

[Toybasher]

As far as I have uderstood the scanpattern works quite differently in the Mig, but covers what could be regarded as 3 bars.

 

(Try to draw the below pattern):

It starts at the left (30°) mid (0°) position.

Then moves to right (30°) mid (0°) position.

Then to right (30°) low (8° declined) position.

Then to left (30°) low (8° declined) position.

Then to left (30°) high (8° inclined) position.

Then to right (30°) high (8° inclined) position.

Then to right (30°) mid (0°) position.

Then to left (30°) mid (0°) position.

Then to left (30°) low (8° declined) position.

Then to right (30°) low (8° declined) position.

Then to right (30°) high (8° inclined) position.

Then to left (30°) high (8° inclined) position.

Then to left (30°) mid (0°) position.

Then starts over....

 

The radar beam is a baseballbat shaped signal with the thick end at the far away position.

This beam is 4,8° and rotates exentric to form a 9° beam inorder to have a "signal even zone".

By the movement between mid, low and high angle (±8°) the beam covers 9/2 (roughly half the beam) + 8 + 8 + 9/2 (roughly half the beam) = 25° (effective only 24° due to the rotating beam form).

 

All this is declined by 3° to compensate for the normal aircraft pitch attitude.

 

This pattern is stabilised between ±70° in roll, but not stabilised in pitch, thus as the descriptions I have tell - the search pattern will follow pitch movement and the "target below", "target inline" and target above" indications are not relative to altitude, but to the Mig's longitudal axis.

 

Look here (in German):

http://www.mig-21-online.de/

Under: Mig-21 "Fishbed" -> Flugzeugsysteme -> Funkmessvisier

 

FinnJ

 

 

Can I see a gif or something? I tried drawing it in paint and got super confused.

[Aginor]

If I understood correctly it would look like the attached picture.

Just follow the numbers.

 

The three bars are each 8 degrees high and 30 degrees wide.

Edited March 15, 2016 by Aginor

[zaelu]

Thanks for the info guys, a bit complex pattern I'd say.

 

I guess it is the only pattern it has, right? How much time it takes for a full scan?

[WildBillKelsoe]

15 seconds for full sweep

[WildBillKelsoe]

so radar is bonkers?

[Aginor]

No, it isn't that bad.

The beam itself looks like a baseball bat (thick end towards the target) which is spinning and covering ten degrees in height and width. So a target may well be covered by more than one scan line.

 

Considering that, this pattern isn't bad at all! It has a good average coverage of the central area. where the plane is facing.

 

Look at this:

http://www.mig-21-online.de/Funkmessvisier/Bilder/Bild_20.jpg

 

EDIT: I just noticed you were talking about the radar of the MiG in DCSW, WildBillKelsoe. Yes, in DCSW right now there is a bug that is going to be fixed.

Edited March 16, 2016 by Aginor

[fjacobsen]

What I did not tell in my above description is that the beam is inclined 1,5° when using the R-3 & R-3S and declined 1,5° using the R-2 missiles.

 

This is relative to the fixed 3° declination.

 

Also in the low altitudemodes the first setting simply removes the low search pattern - effectivly reducing the "bar" scans from 3 to 2 and thus not looking 8° below inorder to reduce ground clutter.

In the second setting this is also true, but additionally the scan is inclined by 1,5° to further reduce ground clutter.

 

So tecnically seen the RP-21 / 22 radar has some relative complex mechanics build in.

 

Question is really how close the LN simulation has come to this, or maybe that in-sim possibilities restricts the full implementation of these mechanics.

 

What I see is not a perfect rendition of the real radar, but I don´t either regard it as bad the way it works right now, but I would expect the radar to be more able to pick up targets being at co-altitude.

 

FinnJ

[foxbat155]

Guys all informations from Mig-21-online.de are devoted RP-21 radar. RP-22 is totally different generation, works different and her angles are bit different. To judge Leatherneck's work we need RP-22 manual, maybe somebody have her and will show. I have manuals only for RP-21.

 

And how looks stabilization mechanism in real antenna:

 

 

 

 

 

 

 

Cheers.

[zaelu]

15 seconds for full sweep

 

ouch

 

so radar is bonkers?

 

I haven't test it too much but in a training mission where I was always going towards 3 targets head on I simply passed by in almost co-alt level flight and I was surprised by that because normally I never failed to acquire them.

 

Guys all informations from Mig-21-online.de are devoted RP-21 radar. RP-22 is totally different generation, works different and her angles are bit different. To judge Leatherneck's work we need RP-22 manual, maybe somebody have her and will show. I have manuals only for RP-21.

 

 

True, maybe the final manual for the module will include something?

[fjacobsen]

Guys all informations from Mig-21-online.de are devoted RP-21 radar. RP-22 is totally different generation, works different and her angles are bit different. To judge Leatherneck's work we need RP-22 manual, maybe somebody have her and will show. I have manuals only for RP-21.

 

And how looks stabilization mechanism in real antenna:

 

 

 

 

 

 

 

Cheers.

 

 

As far as I know the RP-22 is an enhanced version of the RP-21 with a detection range at appr 30 km and slightly different scan angles in the vertical. Even the various controls are very much the same.

 

The pictures are quite interesting, but does not really tell much about the stabilisation mechanism ( what is the stabilisation mechanism and what is the scan mechanism ? - probably it's the same, just being controlled by a mix of inputs from scan and stabilisation control circuitry).

 

So the best info that can be gathered is on the RP-21.

Edited March 18, 2016 by fjacobsen

[foxbat155]

Pictures are just pictures, of course they don't tell anything about stabilization parameters, they just shows that mechanism was quite complicated. Thats why we need real manual.

 

RP-22 it's not just enhanced variant of RP-21. This is totally new construction, next generation radar ( monopulse 2 gen. ). RP-22 is simplified and smaller variant of the RP-S "Smierch" radar from Tu-128 and MiG-25 fighters. Constructors use one of the frequencies from RP-S, and created small package with much less power output ( in the same way was created radar RP-15 "Typhoon" from Su-15T/TM fighter ). RP-21 is evolution of RP-9 ( CD-30 ) from Su-9 and created on RP-1/RP-5 family basis from MiG-17PF/PFU and MIG-19P/PM fighters. Only thing which connecting both radars it's MiG-21.

[Tarres]

Manuals about the MiG-21bis are in Avialogs (English) and in the Polish Air Museum:

 

http://www.muzeumlotnictwa.pl/index.php/digitalizacja/katalog/2309

 

and

 

http://www.muzeumlotnictwa.pl/index.php/digitalizacja/katalog/2308

 

The scan limits are +20º/0º in elevation (fixed) and +-30º in azimuth.

 

The only movements of the antena are the "Low Altitude" mode that sets the antenna in a +1.5º angle upwards to avoid clutter on altitudes below 2000 meters and the "fixed beam" that set the radar in 0º azimuth and -1.5º in elevation.

 

The "up and down marks" according to the manuals, only are representatives of the "relative altitude with the 21" of a contact if the 21 is flying with a pitch of less than 8º.

 

Page 56 of the Pilot´s manual in Avialogs.

Edited March 17, 2016 by Tarres

[foxbat155]

Please read carefully, both manuals polish and english says about radar SCREEN angles not radar itself. Of course this not means some big differences between them but we still don't have precision angle values for radar antenna and no information about antenna move pattern.