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When will we get the radar fixed?


kaboki

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Alright sweet, people who know how radars work

 

1) As seen in this thread, the radar fails to pick up any target once you fly below a certain altitude threshold (say, for instance, below 5000 ft), even if your target is way above the horizon, or even if your target is very close to you - is this realistic behavior?

 

2) if you flip your plane and fly inverted, the radar can now detect all targets no problem whatsoever regardless how close to the ground you are - is it supposed to work like this?


Edited by Elo001
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Fred, I've missed your question earlier. The possible misinformation about radar comes from the manual which states that it operates in ±30° in azimuth, -1,5° and +17° in elevation (p.136 - I reckon it is search mode, although these numbers would be more suitable for target tracking mode). I believe this is how it was modeled since the beginning. I have no idea whether the version of radar LNS studied was any different from the stock one, so I don't know the details.

 

Example also here: http://www.digitalcombatsimulator.com/en/files/921515/

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1) As seen in this thread, the radar fails to pick up any target once you fly below a certain altitude threshold (say, for instance, below 5000 ft), even if your target is way above the horizon, or even if your target is very close to you - is this realistic behavior?

 

Just to note, we need to specify between Above Ground Level or AGL and Mean Sea Level or MSL.

 

You can be 8,000 feet MSL, but only 1,000 feet AGL.

 

In my opinion, this is an important distinction to make and it seems to be related to how the radar is being modeled relative to the ground. If you're flying on the coast, it's not an issue as you should be up higher, anyways. But, if you're fighting over the mountains, this is a definite handicap.

 

Can someone help me understand why a radar would completely shut down below a certain altitude, I can understand that it will have trouble with targets against the ground, but why would it have difficulties picking up targets above the nose against the sky while flying low?

 

We really shouldn't be.

 

In the simplest terms, think of radar as if you're trying to find friends out in a field at night with flashlights. Your eyes are receiving information from that light. It's honestly pretty easy, but the human eye has a limit as to what light it can pick up. Radar has limitations similar to this (even more so, since the radar is sending out a signal and waiting for it to come back as opposed to light beaming directly to you). Now, say someone put a big flood light out in that field.

 

To be a jerk and ruin your lovely game of flashlight tag.

 

The closer you get to that floodlight, the more difficult it could become to pick up other, weaker lights. The same kind of problem happens here with the MiG radar.

 

All that said, we shouldn't be seeing an inability to see targets that can be remedied by a roll.


Edited by MiG21bisFishbedL

Reformers hate him! This one weird trick found by a bush pilot will make gunfighter obsessed old farts angry at your multi-role carrier deck line up!

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Quite a bit wrong with that picture before the topic of negative scan elevation even comes up. The shape should be qualitatively a slab-sided wedge with a section of a sphere at the range-limit like so: http://lomac.strasoftware.com/mirror/Tuto%20Radar%20RWS%20F15-C_files/MODELE.gif

 

The -1.5° is the beam setting for fixed beam. I'll have to check again but the beam may also be shifted for the R-3R missile specifically. This might be the A-23D radar which I think is similar to the RP-21.

 

The RP-21 had various tilt settings (zero elevation positions) for different armament selections, -1.5° for APU-15 (R-3S, R-13), -3.0° generally, -4.5° for APU-7 (RS-2US). This was to compensate for aircraft AOA and in the RS-2US case to ensure that the missile flew into the guidance radar beam. The radar was not (apparently) horizon-stabilized and relied on these "mean AOA" shifts to be acceptably level based on the armament.

 

The horizon-seeking nature of the RP-22 should render these AOA-compensating adjustments irrelevant except of course in the fixed beam case. The RP-22 I believe is not compatible with the RS-2US (LNS saying as much) and this capability fictional.

 

There is the possibility that because I'm not native in Polish that I'm misreading where the "zero" should be for the +-17°40'' (perhaps biased up a bit). But it clearly says +-17°40'' (along with +-28° azimuth) so if its zero is angled up we still have ~40° of elevation range to go with our ~60° of azimuth range.

 

I'm still curious why the "above" "below" marks are only guaranteed valid within aircraft pitch range -25, 8. The center of that range is 8.5° upward. Or the horizon-sensing apparatus is simply asymmetrical in ability.

 

How is a radar going to scan so much area in a few seconds? The RP-21 has a 3-bar scan pattern and covers "one room" (interpretation: 1 bar) in 1.7-2.5 seconds. All three bars plus some vertical travel time is 7-10s. The Spin Scan pattern is about 10 degrees tall (~2 deg overlap) but the bifurcated monopulse beam in the RP-22 is how big? Can it manage to cover the full height in 4 bars? The manual description of waiting 15 seconds to ensure a full scan make a lot more sense now.

 

I have no concrete idea of what the radar should look like if we go beyond the roll stabilization limits. I guess the pattern would turn with the airplane and be misrepresented as still stabilized.


Edited by Frederf
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We'll investigate the inverted flight in the next couple of days.

 

 

Could we get a definite answer on how the radar is supposed to work at low altitudes?

 

I'm flying level 100 meters above ground. Visually acquired a F5, 12 o'clock high, above the horizon, above my nose. No mountains, just flat ground. Range to target 3500 meters (alternative scenario: range is 10000 meters so it doesn't get masked). Target is within the radar field of view

 

Is the radar supposed to detect this F5? Or is the radar supposed to be completely non-functional at low altitudes even when contacts are clearly above your own plane? What about low altitude compensation with the radar being tilted upwards 1.5deg?

 

That'd help a lot to differentiate between intended and bugged behavior

 

Edit:

Not asking how the *real* radar works, simply asking how you intended the modeled in-game radar to work.


Edited by Elo001
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Could we get a definite answer on how the radar is supposed to work at low altitudes?

 

I'm flying level 100 meters above ground. Visually acquired a F5, 12 o'clock high, above the horizon, above my nose. No mountains, just flat ground. Range to target 3500 meters. Target is within the radar field of view

 

Is the radar supposed to detect this F5? Or is the radar supposed to be completely non-functional at low altitudes even when contacts are clearly above your own plane? What about low altitude compensation with the radar being tilted upwards 1.5deg?

 

That'd help a lot to differentiate between intended and bugged behavior

 

Edit:

Not asking how the *real* radar works, simply asking how you intended the modeled in-game radar to work.

 

It should not be vissible. It does not matter that you can visualy see the F-5 or that it is above you.

In this case as it is at 3,5km it is masked by radar returns of primary and side lobes of the ground. So it could very well be shown on the scope, but along with all the clutter.

 

Now if it was in lets say 10-15 km away and above you, I see no reason it should not be seen by radar and shown on the scope, because radar returns from the ground only extend to finite distance.

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There's always been a minimum range on the radar of about 400-600m in all situations. At different heights there will be a band of range showing ground return if there is a return at that angle. From the paragraph text and Arcsine of range vs height we expect the return center to be 5° (1km) 5.4° (800m) below horizon while the main axis is 1.5-2° (depending AOA) above. That may be from the main lobe which has its axis roughly level (remember spin scan pattern so 2 deg up look axis means that the beam lower, upper edge will be -2,+6 degrees at the 6 o'clock and 12 o'clock positions respectively).

 

Note that the Almaz-23 radar is similar (but improved) to the RP-21 "Spin Scan" radar with 30km range and R-3R capability. One of the difficulties of spin scan is that it is so large because the main beam has to circle around the look axis to scan it. This makes scanning near the ground troublesome as during this spin scan at some point you must put the entire main beam below the look axis.

 

Monopulse like RP-22 (DCS MiG-21) is better for scanning near the ground as it can use a single beam along a main axis and listen in a directional manner. It doesn't require the beam to "touch edge" with the target from below.

 

The RP-22 is a distinct improvement over both while still being non-Doppler. Whenever possible we should refer to the RP-22 documentation instead of the RP-21 or A-23, the low altitude compensating functions being different.

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Could we get a definite answer on how the radar is supposed to work at low altitudes?

 

I'm flying level 100 meters above ground. Visually acquired a F5, 12 o'clock high, above the horizon, above my nose. No mountains, just flat ground. Range to target 3500 meters (alternative scenario: range is 10000 meters so it doesn't get masked). Target is within the radar field of view

 

Is the radar supposed to detect this F5? Or is the radar supposed to be completely non-functional at low altitudes even when contacts are clearly above your own plane? What about low altitude compensation with the radar being tilted upwards 1.5deg?

 

That'd help a lot to differentiate between intended and bugged behavior

 

Edit:

Not asking how the *real* radar works, simply asking how you intended the modeled in-game radar to work.

Mig-21 was designed as fighter-interceptor. So do its radar was aimed to track high flying targets at generally known location to which the pilot was directed by ground control. Let's face it, the RP-22SM is really primitive radar that was further limited by the small size of the Mig-21 nose cone.

The Mig-21 flight manual has a special chapter addressing the radar operation at low altitudes.

1. Intercepting targets flying below 2000-3000 meters require special radar operation as the radar becomes receiving ground clutter.

- the antenna should be tilted up by 1,5°-2,0° above the horizon

- the plane must be 300-500 m below the intercepted target

2. The lower the altitude the more the ground clutter becomes an issue in result limiting the maximum range at which the targets can be distinguished from the noise.

It can be that I'm misunderstanding the instruction but it looks like the closer the ground then the top part (not bottom) of the radar screen would be displaying the noise thus making impossible locating the targets further away.

According to the instruction

- at altitude of 1000m the radar screen is highlighted in between distance of 10-13km and more. In other words at altitude of 1000m the targets further than 10 km are not visible on the screen or being more specific bland with the return signal from ground clutter.

- at altitude of 800m highlighted of 7-10 km and more

3. While not specifically stated in the instruction an conclusion can be drawn that intercepting targets flying at or below 300-500m is not possible as the condition to fly below 300-500 of the target can't be met.

4. I didn't find it in the manual (id didn't read it all) but we can also assume that there is a minimum range as described by Frederf.

 

The bottom line is that the Mig-21 radar in DCS seems to generally work correctly on the low altitudes. The specific values could be tested and there may be an issue with the visualization but as long as the implementation is reassembling the real thing it’s great.

Note also that DCS doesn't provide real radar simulation. If I recall the Mig-21 was the first module to bring the realistic radar behavior. I think we should give more credits to LN for that.

The issue though is that the targets should not magically appear in inverted flight.

 

 

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F/A-18, F-16, F-14, M-2000C, A-10C, AV-8B, AJS-37 Viggen, F-5E-3, F-86F, MiG-21bis, MiG-15bis, L-39 Albatros, C-101 Aviojet, P-51D, Spitfire LF Mk. IX, Bf 109 4-K, UH-1H, Mi-8, Ka-50, NTTR, Normandy, Persian Gulf... and not enough time to fully enjoy it all

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Mig-21 was designed as fighter-interceptor. So do its radar was aimed to track high flying targets at generally known location to which the pilot was directed by ground control. Let's face it, the RP-22SM is really primitive radar that was further limited by the small size of the Mig-21 nose cone.

The Mig-21 flight manual has a special chapter addressing the radar operation at low altitudes.

1. Intercepting targets flying below 2000-3000 meters require special radar operation as the radar becomes receiving ground clutter.

- the antenna should be tilted up by 1,5°-2,0° above the horizon

- the plane must be 300-500 m below the intercepted target

2. The lower the altitude the more the ground clutter becomes an issue in result limiting the maximum range at which the targets can be distinguished from the noise.

It can be that I'm misunderstanding the instruction but it looks like the closer the ground then the top part (not bottom) of the radar screen would be displaying the noise thus making impossible locating the targets further away.

According to the instruction

- at altitude of 1000m the radar screen is highlighted in between distance of 10-13km and more. In other words at altitude of 1000m the targets further than 10 km are not visible on the screen or being more specific bland with the return signal from ground clutter.

- at altitude of 800m highlighted of 7-10 km and more

3. While not specifically stated in the instruction an conclusion can be drawn that intercepting targets flying at or below 300-500m is not possible as the condition to fly below 300-500 of the target can't be met.

4. I didn't find it in the manual (id didn't read it all) but we can also assume that there is a minimum range as described by Frederf.

 

Even if i meet your perfect conditions, i can't get targets to show up on radar before I fly inverted. I mostly stay at 10000 feet wich is above the ideal conditions for the radar and a have targets above me, still no luck. It just doen't work as you describe, if it did i would be a happy bunny... I know the radar is supposed to be for very limited uses, but right now it's useless... Now I stopped loading Radar guided missiles, bacause I never get too use them, waste of space...

 

For me it seems the radar in inverted flight is like it supposed to be when flying normally, still shitty, but more useful....


Edited by kaboki

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Mig-21 was designed as fighter-interceptor. So do its radar was aimed to track high flying targets at generally known location to which the pilot was directed by ground control. Let's face it, the RP-22SM is really primitive radar that was further limited by the small size of the Mig-21 nose cone.

 

This.

 

The MiG has a premium on space. We shouldn't be burying our faces in the instruments. You shouldn't be doing that in the Eagle, let alone in something as primitive as the Fishbed.

 

In all honesty, you're really better off looking for contrails on an intercept.

Reformers hate him! This one weird trick found by a bush pilot will make gunfighter obsessed old farts angry at your multi-role carrier deck line up!

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This.

 

The MiG has a premium on space. We shouldn't be burying our faces in the instruments. You shouldn't be doing that in the Eagle, let alone in something as primitive as the Fishbed.

 

In all honesty, you're really better off looking for contrails on an intercept.

 

I think this is drifting a bit off topic. :)

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Even if i meet your perfect conditions, i can't get targets to show up on radar before I fly inverted. I mostly stay at 10000 feet wich is above the ideal conditions for the radar and a have targets above me, still no luck. It just doen't work as you describe, if it did i would be a happy bunny... I know the radar is supposed to be for very limited uses, but right now it's useless... Now I stopped loading Radar guided missiles, bacause I never get too use them, waste of space...

 

For me it seems the radar in inverted flight is like it supposed to be when flying normally, still shitty, but more useful....

Use the IR missiles and you don't need the radar at all! For the long distance I always use SAR missiles and very short range the IR missiles and radar turned off.

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Use the IR missiles and you don't need the radar at all! For the long distance I always use SAR missiles and very short range the IR missiles and radar turned off.

 

Well I bought the product to use all it's weapon systems, and not curcumvent the problems by using only half of it's capabilities...:noexpression:

 

Did the real pilots also get tired of the non functional radar and jsut loaded IR missiles?

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I did some testing with three F-5E3 in front of Mig-21 in distance of 7, 10 and 15 km. Test was done at different altitudes. There was no problem with obtaining the target on the radar at altitudes higher than ~1000m.

 

- 3500m: all targets visible, ground clutter not noticeable,

- 3000m: all targets visible, ground clutter noticeable, enabling ground filter results in almost clear picture

- 2500m: all targets visible: ground clutter becomes highly apparent

- 2000m: as above but it becomes hard to see targets in ground clutter area without enabling the filter

- 1500m: all targets visible but those in clutter area only after enabling the filter

- 1300m - 1000m: radar started to loose the targets, from time to time they appeared on the radar but relying on obtaining a visual signal was not reliable.

 

I have to admit that what I was expecting to see but was not able to replicate. Maybe it's possible with more testing:

- while dropping the altitude, the further targets disappearing first, generally I was seeing all of them or none

- flying 300-500 below the target with antenna tilted up didn't make the targets that were not visible to appear. I couldn't not create a situation when tilting the antenna up would make a difference.

 

Overall at least the testing that I've manged to do in SP shows that the radar in DCS works really close to what the Mig-21 instruction is saying about the real radar.

 

I've discovered one problem though, when setting the altitude of AI plane to less than 1000 m AGL after mission start it rapidly looses the altitude to ~500 m which made precise testing at small altitudes difficult and too time consuming.

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Edited by firmek

F/A-18, F-16, F-14, M-2000C, A-10C, AV-8B, AJS-37 Viggen, F-5E-3, F-86F, MiG-21bis, MiG-15bis, L-39 Albatros, C-101 Aviojet, P-51D, Spitfire LF Mk. IX, Bf 109 4-K, UH-1H, Mi-8, Ka-50, NTTR, Normandy, Persian Gulf... and not enough time to fully enjoy it all

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Mig-21 was designed as fighter-interceptor...

 

Check out section 3.6 pages 87-93.

 

The radar usage is apparently broken into 3 altitude bands: 10km and over are clear of ground effects, 3-10km recommended use of the first compensation ability, and below 3km recommended use of the low-altitude mode.

 

The previous radar RP-21 also made a variable number of "up" or "down" marks it seems based on target width. I wonder if the RP-22 makes such multiple marks as figure 7.6 suggests it might. Could 2 up, 1 down be an an elevation between 2 up, 0 down, and 1 up, 1 down?

 

I also take back the notion of the target stroke being a digital symbol. It's just an analog representation of the aircraft return (being very limited in depth and having pronounced width) which also varies with target size and closeness.

 

The RP-21's ground compensating mode is clear having stared at the picture enough. It is a 3-bar scan and the first position simply prevents the lower bar and then shifts the 2 bars upward at the maximum setting, the transmit power being automatically reduced (detection performance being less) in both cases.

 

I wonder how many bars the RP-22 has (4? 5? 8?). Does it remove them one-by-one as a function of altitude?

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Interesting questions Frederf. I'll read the instruction and see if I can find answers.

F/A-18, F-16, F-14, M-2000C, A-10C, AV-8B, AJS-37 Viggen, F-5E-3, F-86F, MiG-21bis, MiG-15bis, L-39 Albatros, C-101 Aviojet, P-51D, Spitfire LF Mk. IX, Bf 109 4-K, UH-1H, Mi-8, Ka-50, NTTR, Normandy, Persian Gulf... and not enough time to fully enjoy it all

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I did some testing with three F-5E3 in front of Mig-21 in distance of 7, 10 and 15 km. Test was done at different altitudes. There was no problem with obtaining the target on the radar at altitudes higher than ~1000m.

 

 

strange because in MP i can't locate targets even at 5km altitude, and when they are occasionally detected at 30km, they disappear from the radar scope as i close in. Maybe the new MP netcode is cocking things up.

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New(ish) gosh-darn information.

http://forums.eagle.ru/attachment.php?attachmentid=105161&d=1411896672 (Czech).

 

On the second page is a picture of a radar scan pattern composed of 5 bars interlaced with 5 more bars half offset in elevation from the first. The angular limits in the vertical are -1.5 to +17 the initial scan being left to right on the bottom bar and in the following sequence:

 

1R, 3L, 5R, 7L, 9R, 10L, 8R, 6L, 4R, 2L, repeat.

 

This "stabilization of the scan area" is said to be from +8 to -25. It would make the most sense that this allows the airplane to pitch up the most and down the least. 17+8=25 and 1.5+25=26.5, roughly equal. The other interpretation is that the radar can somehow look up to +17 above the horizon when the nose is 25 degrees below the horizon for a total angle of 42 degrees while only being able to look down 9.5 (pitch +8, scan -1.5).

 

It's worth a note that this picture distinctly shows the MiG at a low altitude if this can be taken to mean anything. The lower limit is given as +-1.5 as the bottom limit (or in fact the entire pattern?) is lifted 1.5-2 over horizon at the low altitude setting.

 

18.5 degrees from center bar #1 to #10 and a given beam size of 3° produces bars with substantial overlap.

 

The scan time of 3s might be to traverse all 633 degrees of antenna pattern or just 318.5 (odds or evens) of it or just a single bar. I don't know what angular rate is reasonable.

 

Later the "destination search mode" is shown to have +-28 x +-17.666 "radar field of view." What is this and why is it different than the table and picture on pages 1 and 2? Is it actually some way for Lazur to display onto the radar screen directly? I feel it is not autotracking mode.

 

I invite you to look for yourself the post, PDF, and 6 hand written notes http://forums.eagle.ru/showthread.php?t=131078

 

In my mind there are two fighting ideas about the search region. Neither one makes sense on its own but they contradict each other.

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After reading the pdf, the only ambiguity comes from the table of operation. However since it's about the radar, I assume those angles belong to radar antenna movement limits when it tries to compensate and gyro-stabilise (as long as it's within those limits mentioned in the table). Also the second part which describes the radar screen itself and lazur system is translated less carefully both in czech and slovak language and contains some typos, more ambiguity etc unlike the first part, so the sources might vary.

 

It states scan area to be ±30° horizontal and +17° ±1,5° vertical in search mode (which would coincide with game manual), with gyro- stabilisation of ±70° on longitudinal axis and +8°, -25° on lateral axis.

 

(The words used are little bit misleading as 'zdvih' might mean here in context the tilting upwards, but usually it means rise, or stroke (for piston engines), while word 'pad' literally means the fall or rapid descent, but most likely it means here downward tilt) - yet the latter word would fit more describing the attitude of plane in dive, instead of radar antenna movement).

 

Following the target in the tracking mode is ±30° vertically and horizontally, 3sec repeating scan time, 500m blind zone in front of radar, max time with radar on is 30min and standby+on is max 90min per flight. Of note is the ability to search, lock and track the target reliably even if it utilises passive countermeasures in frequency of 10 chaff charges per 100m of distance - in other words almost impossible to disrupt by passive countermeasures. The width of radar band/beam is 3°. Altitude compensation mode is as we know it: off, signal filtering/compensation and tilting the antenna upwards (it states +1,5° +2° above horizon). Fixed beam mode is at -1,5° downward tilt, horizontally centred (the lower X mark on the fixed net). Also confirmation about button #2 being used for locking targets which are flying at low speeds, #6 anti passive countermeasures filter, #7 anti active and passive countermeasures filter, #8 anti active countermeasures filter (where the range is fixed between 12 and 18km distance). Only one filter might be active at the time.

 

If you have any questions regarding other parts of the pdf, let me know and I will doublecheck.


Edited by Spectrum Legacy

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Given the +17/-1.5 scan zone do you think the pitch limits are +25/-8 or +8/-25? In order words is the pitch limit what the airplane can do or what the radar antenna can do? I drew both situations. The sum of antenna angles 8+1.5° and 25+17° (or 8+17 and 25+1.5 is the same) is what is required to complete the scan inside pitch limits given. This is 51.5°. For one picture this requirement is distributed +42° -9.5° and for the other picture is +25° -26.5°.

 

Also "3 seconds" is the repeat scan in the auto tracking mode? Is it given an estimate to complete a scan in the overview mode?

 

+-17°40'' is a total of 35°20''. This is nearly equal to 25+8=33° which is apparently the total freedom of scan zone positioning in the vertical. There is a small difference which should have an explanation.

 

Beam width is said to be 3°. If the antenna lateral movement is +-28° then 2° are being detected outside of the limit of axis pointing. Is the same true for the vertical? In an extreme case when the bottom "bar" of scanning is happening at -1.5° then are targets being detected as low as -3.5°? At the top bar when the axis is pointed 17° high are targets detected as high as 19°? The bar scanning diagram isn't so precise to differentiate between dish axis direction and detection angular limits.

 

I admit it was hasty to say the scan zone is symmetrical but it is so confusing why the RP-21 was 24° full height scan with its center tilted down 1.5, 3.0, or 4.5 degrees below the nose. The previous radar was looking nominally 12 degrees below the horizon when employed at high altitude. It had an inferior range of course. It's an exceptional reduction in ability for RP-22 to look so weakly downward that is not satisfactorily explained.

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Edited by Frederf
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Frederf,

 

It's your second image. These are antena's stabilization limits: +/-70deg roll, pitch +8, -25deg.

I have attached image from the manual (Translation is mine).

It also says that if you are intercepting in low alt (<3km), tactic should be that you are lower then target by 400-500m @ range 5-6km for lockon.

1668868252_MIG21RP22SMA.thumb.jpg.23b9030eff1eb26185e74ad3597f6343.jpg

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