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

We have encountered a strange issue with the Flanker radar in DCS:

When you fly below 1500m AGL and roll over more than 135° left or right, the radar will no longer work. Lock will fade and no targets will be shown on the scope when the lock is gone.

Under this condition (inverted and below 1500m AGL) the Radar will stop working at any range to the target.

This cannot be intentional? To me it looks like a bug.

I can confirm the lost lock issue, though in my case, after the lock is lost, the radar continues to function normally and the contact reappears in both SCAN (ОБЗ) and TWS (СНП). This is in SP.

EDIT: I should clarify. The contacts reappear once you roll more toward upright. As long as you are inverted, no contacts appear. Even without a lock, any contact disappears once you roll to the degree you specify and the radar no longer displays anything.

Main thing here is NO MISSILE GUIDING... once if this happens missile not tracking

Rolling with RL only >>> lost lock >>> no missile guiding

Rolling with EORL >>> EOS lock will works only >>> again no missile guiding

Problem here is that system losing lock or switching on EOS while we guiding our ER missile. Only EO lock exist and we need shot new missile to force RL >>> EORL or manualy EO OFF to force RL.

This target have 0 chaffs - missiles are not chaffed but unguided because no RL.

Hi

It probably has to do with the sidelobe clutter described in the F-15 manual since you are trailing the other aircraft at roughly the same speed.

From the F-15 manual:

The guard horn is attached to the slotted array in flat-plate radar antennas like the APG-63 and scans together with it for good compensation in all scan directions. In Russian Cassegrain radars like the N019 and N001 however, the guard horn is not attached to the scanning reflector but is rather fixed and aimed in a downward direction. 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. During normal scanning operation in search mode, the entire radar Cassegrain antenna housing is roll-stabilized on a rotating gimbal to keep it oriented with the horizon. In this mode, search targets can be lost from the scope if the fighter roll exceeds the limits of the rotating gimbal (110-120 degrees angle of bank).

SnapRoll

Not implemented on F-15C, tested. Losing lock if you are inverted below 1500m, Where is the 1500m coming from, I understand if it was at 500m but at 1500, radar go off if the bandit is above you.

Not implemented on F-15C, tested. Losing lock if you are inverted below 1500m, Where is the 1500m coming from, I understand if it was at 500m but at 1500, radar go off if the bandit is above you.

I was only quoting the F-15 manual. The F-15 does not have this problem. It talks about the limitations of the Russian radars.

And yes, I would also expect this to happen at a much lower altitude. I am not saying it is all correct. It could be this effect but not quite properly implemented.

In the movie from Falcon it is a closing target. So it should definitely not happen there.

Interresting find SnapRoll.

Maybe this is intended to model this behaviour. But it just shuts off the radar no matter what the target aspect is. He can be hot and 5 km in front of you, and your radar will lose lock. According to that F-15 manual it would only affect lock on a a cold bandit.

I hope we are not making Su-27 after F-15s manual, Is this somewhere to find in Su-27?

I hope we are not making su-27 after F-15s manual, that would be over the top. Then lets model AIM-120 from what it say in Russian Su-27 manuals about it. Is this somewhere to find in Su-27 Manual?

It's the FC3 ED manual...

Interresting find SnapRoll.

 

Maybe this is intended to model this behaviour. But it just shuts off the radar no matter what the target aspect is. He can be hot and 5 km in front of you, and your radar will lose lock. According to that F-15 manual it would only affect lock on a a cold bandit.

I have not tested it and yes, I totally agree.

In my test the target was hot not cold.

That information comes from the (RL, non-ED) flanker manual. This isn't exactly 'news' for a cassegrain radar, or any radar that requires guard horn. The specifics of the implementation could be in question though.

I hope we are not making Su-27 after F-15s manual, Is this somewhere to find in Su-27?

A better and still simple approximation would be to reduce the sensitivity a bit just as it gets reduced when you get lower than 1500m.

That information comes from the (RL, non-ED) flanker manual. This isn't exactly 'news' for a cassegrain radar, or any radar that requires guard horn. The specifics of the implementation could be in question though.

It would not lose lock or just turn the radar off, It would have harder to keep lock or would not keep it as well passed 120 degrees at low alt.

We'll, you have a backup for this exact reason :)

Do you have a back up that you loosing lock, if so, plz let me see. Where did ED get 1500m from?

My memory from reading Overscan's guide to Russian Radars is that this doesn't sound too dissimilar to the limitations described there, and that there were quite a few limitations on the Su-27 (& MiG-29) radar operation that would disgruntle a few players if E.D. were ever to do a full fidelity module of the Su-27S.

Still - Having your capabilities downgraded in the name of realism is easier to swallow when the realism is applied even-handedly...

I'd be applauding E.D.'s implementing the limitation - if they weren't adding imaginary weapons and pylons to the Ka-50 at the same time...

My memory from reading Overscan's guide to Russian Radars is that this doesn't sound too dissimilar to the limitations described there, and that there were quite a few limitations on the Su-27 (& MiG-29) radar operation that would disgruntle a few players if E.D. were ever to do a full fidelity module of the Su-27S.

 

Still - Having your capabilities downgraded in the name of realism is easier to swallow when the realism is applied even-handedly...

 

I'd be applauding E.D.'s implementing the limitation - if they weren't adding imaginary weapons and pylons to the Ka-50 at the same time...

Some other capabilities would get implemented that would make the flanker 2 time better not weaker. A lot of people would not disgruntle to fly it just for that reason.

Do you have a back up that you loosing lock, if so, plz let me see. Where did ED get 1500m from?

Like I said, you already have a back up for this, so use it. The IRST was added exactly for these situations, not for 'sneak attacks'.

It's a back up for the crappy radar. In RL.

Later versions of the flanker got a much improved radar both on the computing power side and the antenna (planar array vs cassegrain) ... But that's not the model you have.

Do you have a back up for not losing it? The documentation is more against your position than not.

 

Like I said, you already have a back up for this, so use it. The IRST was added exactly for these situations, not for 'sneak attacks'.

It's a back up for the crappy radar. In RL.

Later versions of the flanker got a much improved radar both on the computing power side and the antenna (planar array vs cassegrain) ... But that's not the model you have.

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.

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.

Some other capabilities would get implemented that would make the flanker 2 time better not weaker. A lot of people would not disgruntle to fly it just for that reason.

Maybe, but the N001 has the same processor as and a scaled up version of the antenna from, the N019.

The N019's beam is only stabilised up to 120º in roll and +40º/-30º in pitch - so the 'feature' that has been implemented seems fair enough...

Before various upgrades both had the same radar modes, including:

"Encounter" mode (target closing):

(…)uses a High PRF mode which can detect closing targets only in the velocity range of 230 - 2500km/h at altitudes from 30m to 23,000m. The display is calibrated to a maximum range of 150km.

 

Lockon and transition to tracking mode takes 2 to 7 seconds in Encounter mode.

 

Note that in Encounter mode, a target that changes direction to a tail-on engagement may be lost even when in tracking mode, if it is no longer closing.

So two to SEVEN seconds to get a lock, no detection if the targets closing speed is less than 230km/h, and if the target turns away, you'll probably lose lock even if you are in STT.

Pursuit mode won't detect targets receding at less than 210 km/h, and:

In practise it is used only when necessary, as it is prone to displaying false targets from ground clutter especially at low altitudes. Marsh land, marshy forests and flood plains give greatest clutter problems. When multiple false returns are present, the pilot should compare visible targets with the calculated target range supplied by datalink from GCI controller to determine the correct target.

Interleaved mode will detect targets approaching at speeds greater than 230km/h or receding at speeds more than 210km/h

(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:

It is considered by pilots to be quite problematic, overloading the data computer and generating numerous false returns

Do you have a back up for not losing it? The documentation is more against your position than not.

 

Like I said, you already have a back up for this, so use it. The IRST was added exactly for these situations, not for 'sneak attacks'.

It's a back up for the crappy radar. In RL.

Later versions of the flanker got a much improved radar both on the computing power side and the antenna (planar array vs cassegrain) ... But that's not the model you have.

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

Ain't that the limitation from the radar roll stabilization that is required to be done to keep radar wave polarization intact?

Meaning, once you roll past the radar roll gimba limit, your radar polarization is gone and can't detect the returns.