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Su-27 / Su-33: No Radar when inverted below 1500m


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(Meaning targets with a relative ground speed of between +230km/h & -210km/h won't be detected. That's a big notch, then it will take between 2 and 7 seconds to re-acquire the lock).

 

& it does automatically mimic the functions of TWS, but:

 

IIRC that is from the Su-27SK manual, that the western aircrafts notch is as well from 70-80 degree toward the radar. So it is not exact 90 degree but enough that you put western fighter to your 8-10 clock and 2-4 clock position and you are perfectly notching.

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It could also be that the change in structure forces the system to redo a series of calculations to ensure the exact route of the missile, given the computational capacity of the processors of that time it may be that too many movements in a restricted time space send the computer in "tilt". The calculations are perhaps not so complex but must take place within a given time, in particular I think that the most difficult moment is when the missile goes at maximum speed in its path.

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Fair question; I don't know, you'll have to ask Chizh about that - he had some comments on this, but I only vaguely remember that something was said about this, not what was said.

 

Just asking... i don't know how that thing works in RL. But logic tell me that if Radar Lock can point EO on target and lock by same weapon system then EO can send info trough same system to the Radar and relock target by radar lock.

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At the distances you would expect to use this, I imagine the datalink would be a non-issue.

 

I also wonder if the radar should keep illuminating if a missile has been launched and the system switches to EO backup.

From my understanding the radar would still be slaved to the EO system and even if the radar itself does not have a lock anymore there is no need to stop illuminating. Maybe there would be no datalink updates for the missile when the target is out of the laser rangefinder limits, but the homing of the missile seeker itself should still work.

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Where is yours?

 

Where is you data from that the radar is losing lock passing 120 degree in roll apart from EDs F15 manual?

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The angle depends on your speed. The more speed, the smaller the angle, since the notch is not about the angle but about the closure.

 

IIRC that is from the Su-27SK manual, that the western aircrafts notch is as well from 70-80 degree toward the radar. So it is not exact 90 degree but enough that you put western fighter to your 8-10 clock and 2-4 clock position and you are perfectly notching.

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...

 

Just asking... i don't know how that thing works in RL. But logic tell me that if Radar Lock can point EO on target and lock by same weapon system then EO can send info trough same system to the Radar and relock target by radar lock.

I’m pretty sure I have that info at home but won’t be able to look it up until tomorrow. IIRC, with EOS as the primary, radar is in a quasi-tracking mode used for range information. But there might be more to it than that.

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The angle depends on your speed. The more speed, the smaller the angle, since the notch is not about the angle but about the closure.

 

Yes it does, just like it is written in the manual for the common speeds.

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Yes it does, just like it is written in the manual for the common speeds.

 

& just like I posted above...

 

 

Originally Posted by 100KIAP_Falcon View Post

 

Just asking... i don't know how that thing works in RL. But logic tell me that if Radar Lock can point EO on target and lock by same weapon system then EO can send info trough same system to the Radar and relock target by radar lock.

 

IRL, EOS works in conjunction if 'Automatic' (interleaved) mode is used, but not in encounter or pursuit modes

Cheers.

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Backup? For what is backup? To just lock and show you where is target and we need manualy relock with radar even system automatic switch from RL to EO. If system is so smart as is why is not enough smart to relock with RL (and continue guiding missile) if EO still know where is target. (RL already smartly pointed where is target to EOS - so why not from EO to RL automatic too).

 

Just asking... i don't know how that thing works in RL. But logic tell me that if Radar Lock can point EO on target and lock by same weapon system then EO can send info trough same system to the Radar and relock target by radar lock.

Unless I'm misunderstanding you, how you say it should work is exactly how it works in the sim. If you have a SARH missile selected and are within range for the OEPS to lock onto the target, the target is automatically relocked as you roll more upright and you have the launch cue:

 

 

According to the RW Su-27 manual I have, when the OLS locks the target, the lamp under the "RLS Lock" lamo on the "warning" panel should also illuminate. In the sim, however, it doesn't. Or, at least not both at the same time. Only the primary lock illuminates. The manual makes it sound as if both are lit. But I could be misinterpreting it.


Edited by Ironhand

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Yeah, from ILV/ABT will relock. But from HI/ППС will not. (Not sure if that is correct)

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Yeah, from ILV/ABT will relock. But from HI/ППС will not. (Not sure if that is correct)

Perhaps not from ОВЗОР but it will in СНП as per the manual. Presumably ЗАДНЯЯ ПОЛУСФЕРА as well, though I haven't tested the latter specifically.

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...

IRL, EOS works in conjunction if 'Automatic' (interleaved) mode is used, but not in encounter or pursuit modes

Out of curiosity, can you cite your source for this info. I can't find any such distinction in my source material.

 

Yeah, from ILV/ABT will relock. But from HI/ППС will not. (Not sure if that is correct)

Given what we've been talking about and Weta43's statements, I took your reply at face value and didn't investigate. Turns out that the two systems interact in the same manner as they do in the video (that I linked a few replys back) whether using the Auto, Front Aspect (HPRF), or Rear Aspect (MPRF) settings.

 

 

@wasserfall, If you're not having any luck, PM me. The links I used to come up with through Google are now dead links.

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Can anyone with a real Su-27 or MiG-29 manual confirm the complete loss of radar function when rolling more than 120° at lower altitutes?

 

To me it seems that such a significant restriction would have to be mentioned in the manual.

 

I haven’t run across it so far in the Su-27 manual I have. It addresses false returns at low altitude, etc. but I haven’t seen anything on loss of function during a roll. Then again, that’s not to say it isn’t covered in a different manual.

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You will have to ask ED directly. The devs have access to resources/knowledge about these particular aircraft and systems that we do not and will not have for a long time.

 

I don't believe anyone else on the forums can directly answer your question.

 

Can anyone with a real Su-27 or MiG-29 manual confirm the complete loss of radar function when rolling more than 120° at lower altitutes?

 

To me it seems that such a significant restriction would have to be mentioned in the manual.

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  • 6 months later...

Continuing discussion started in a different threat:

Because the gimbal only rolls 120 degrees and the compensation horn filter is fixed. Think of it like sunglasses where the top is made darker then the bottom so it shades the sun. Wear the glasses upside down and you can’t see the ground very well. If it was a bug it would probably happen at any altitude but what we are talking about out only happens at less then 1500m AGL, just as if ground clutter has something to do with it:)

 

Only that the ground clutter will be filtered out when a target that is flying towards you, because the doppler shift of the ground is far less than the doppler shift of the target. They are in completely different spectra that do not overlap. This is even said in some MiG-29 document.

cWKcm05.png

 

Using Yandex OCR:

When the target is moving on a collision course, the spectral components of the target signal are located in an area that is free of interference components of reflections from the ground.

 

Even the DCS F-15C manual says that. It is talking about targets that are flying away where the reduced sidelobe compensation can break a lock.

 

Banking the fighter at low altitude during a radar lock on a

fleeing target can thus rotate the compensation horn away from the ground, degrade the sidelobe compensation and break the lock due to ground clutter.

 

But in no MiG-29 document I have seen anything about the inability of the radar to work at all when <1500m and inverted.

 

How are radar guided missiles engaging targets in look down situations without a compensation antenna? Is the seeker of a R-23R missile better than the radar of a MiG-29/Su-27?


Edited by BlackPixxel
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How are radar guided missiles engaging targets in look down situations without a compensation antenna? Is the seeker of a R-23R missile better than the radar of a MiG-29/Su-27?

 

The missile is stabilized to horizont so they do not fly to limits of their gimbals as they don't need to roll?

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The missile is stabilized to horizont so they do not fly to limits of their gimbals as they don't need to roll?

 

So the radar in the MiG-29/Su-27 has to be aligned with the horizon on roll otherwise it cannot track?

 

The radar is locked on roll into its place without any stabilisation in any mode except the BVR mode. This would mean that a target locked in any other mode would be lost as soon as you bank more than 0° (because then the radar has the same roll angle as it has when you tilt more than 120° in BVR mode).

 

 

In general it would be nice to have an image of the compensation antenna, or at least the location. I would really like to know where it is exactly.


Edited by BlackPixxel
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Su-27 N001:

Originally intended to significantly outperform the AN/APG-63 of the F-15, with a 200km detection range, in reality this goal proved impossible for NIIP to achieve. It was intended to use an all new design antenna, featuring electronic scanning in elevation and mechanical scanning in azimuth. This would give excellent multitarget engagement capability, and use of the MiG-31's R-33 was envisaged. This design proved overly ambitious, and was simply unachievable for a mass production radar given the state of the Soviet electronics industry in the early eighties. In May 1982, it was decided that the NIIP designed digital computer and antenna were simply not up to scratch, nor likely to become so in the near future.

Phazotron's N019 had already reverted back to an improved version of the Sapfir-23ML's twist-cassegrain antenna to replace its problematic flat-plate antenna. It was decided therefore to use major components from the N019 radar, including a scaled-up copy of its twist-cassegrain antenna and the TS100 processor. By March 1983, the redesign was complete, though the resulting radar was nowhere near as good was intended. Instead of 200km, detection range barely reached 140km even against a large bomber.

 

So the N001 is in large part a scaled up version of the N019 from the Mig-29, using the same processor and a scaled up version of the antenna.

 

The N019 antenna limits are :

 

The N019 radar weighs around 385kg in total. It is a pulse-doppler radar operating in X band around 3cm wavelength. It uses three basic operating regimes. High PRF radar mode for optimal detection of closing targets, medium PRF mode for optimal detection of receding targets, and an interleaved high/medium PRF mode for all aspect detection. It uses a guard channel for sidelobe suppression. SARH Illumination and main channels use different frequencies within the X band, and are multiplexed in time. Individual aircraft can be preset on the ground to different frequencies to avoid mutual interference during group operations.

 

N019 Master oscillator

Scanning cycle times are 2.5-5 seconds depending on mode.

 

Beam width is 3.5º, which determines the minimum separation of two targets in azimuth.

 

The radar beam is stabilised up to 120º in roll and +40º/-30º in pitch.

Cheers.

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We are aware of the gimbal limits of the radar.

 

It does not mean that the radar is unable to work when it is inverted, it just means that it is no longer aligned with the horizon on roll. That is all.

 

And in all modes except for BVR mode the radar does not even use the roll stabilisation at all, it is locked as if there was no roll gimbal.

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