Question about R27ER and R27R missiles (SARHM)

[4cAleksa]

If I lock the target and launch a missile and right after that if I lock diferent target, missile will not seek that new target but if I switch back to old target than it will.

It mean that missile is able to remember what target was locked at the begining... ????

 

Is it bug or not?

 

Tracks are here.

http://www.surlalab.com/4c/2005.zip

[Octav]

If I lock the target and launch a missile and right after that if I lock diferent target, missile will not seek that new target but if I switch back to old target than it will.

It mean that missile is able to remember what target was locked at the begining... ????

 

Is it bug or not?

 

Tracks are here.

http://www.surlalab.com/4c/2005.zip

 

Bug...

At least in the inertial/radio correction phase, the fighter's datalink sends corrections to send the missile to the target it tracks, so if you switch targets the missile will follow you. In the final, semi-acive phase, if the targets are too spaced apart, the missile might loose the target, and miss.

 

Octav

[Han]

There is a bug. BUT. Another :)

Radio-command (correction) homing can't be restored after fighter radar have lost it's target once. For R-27 it is 100% information, for ARH - no another information.

We know that re-lock is possible only on self-homing stage for SARH and possible for ARH. For SARH it is only in very narrow angle of view of missile, becourse missile is not scanning, ARH is csanning and re-lock possible in wider angle, but there will be a delay becourse scanning takes a time.

[S77th-GOYA]

Let me see if I understand that. The R-27 will not track to a reacquired target until it reaches the final semi-active homing stage? When does this stage begin?

[Octav]

There is a bug. BUT. Another :)

Radio-command (correction) homing can't be restored after fighter radar have lost it's target once. For R-27 it is 100% information, for ARH - no another information.

We know that re-lock is possible only on self-homing stage for SARH and possible for ARH. For SARH it is only in very narrow angle of view of missile, becourse missile is not scanning, ARH is csanning and re-lock possible in wider angle, but there will be a delay becourse scanning takes a time.

 

Hello Han,

Can you tell me your source? My sources tend to say the contrary. The missile is doing inertial navigation in the first phase, and the radar sends target coordinates updates, during this phase. So, if the lock is broken, the missile will navigate to the last known interception point, and if the radar reaquires lock, it will start sending new information.

Octav

[D-Scythe]

Hello Han,

Can you tell me your source? My sources tend to say the contrary. The missile is doing inertial navigation in the first phase, and the radar sends target coordinates updates, during this phase. So, if the lock is broken, the missile will navigate to the last known interception point, and if the radar reaquires lock, it will start sending new information.

Octav

 

But the datalink to SARH missiles isn't really modelled in Lock On - otherwise, silent launches like the AIM-120 in TWS mode would be possible until the launching aircraft had to switch to SST lock in the end-game. I think Han meant that when SARH missiles guide to the reflection of the narrow SST radar beam, if the launching fighter switches to another target widely spaced elsewhere, the SARH seeker may not be able to pick up on the radar reflections bouncing off of this new target that's far away.

 

However, why would there be a delay in ARH missiles? Datalink for it is modelled in Lock On, thus when there's a switch in targets or a relock after lock was broken, the missile should immediately guide itself to the new target, unless it acquired the target already on its own radar. Reaquisition of targets by active radar and IR missiles take too long IMO - in the Combat Archer video, an AIM-9 was decoyed by flares, reacquired its target, and decoyed again twice more before its motor burned out (at which point it missed already).

[GGTharos]

I wouldn't call what you saw in teh Archer video 'reacquisition' :) I would guess that the missile was actually flying pretty dumb from the get-go, until finally the error became so big it sent it up like a ... rocket :D

 

But that's because I have a bit of insight into how the seeker works (and thus potentnially how it affects the guidance section) ... but nothing specific.

[Han]

Hello Han,

Can you tell me your source? My sources tend to say the contrary. The missile is doing inertial navigation in the first phase, and the radar sends target coordinates updates, during this phase. So, if the lock is broken, the missile will navigate to the last known interception point, and if the radar reaquires lock, it will start sending new information.

Octav

About R-27?

Su-27SK flight manual, MiG-29 documents.

There is courrent words: If target is lost during missile fly, than radio-correction for a missile will be newer restored.

Also, N-001 and N-019 can provide provide radio-correction only for TWO missiles simultaneously.

 

Which sourses you have? Please tell us, you may provide your sources to us? You may answer to:

chizh@eagle.ru

han@eagle.ru

[Han]

While we have no info that after fighter have re-lock target the new radiocorrection will be send to an "old" missile, even if it is an ARH.

To find a new target aidless the ARH needs a time becourse the scan zone is wery wide (120° cone, F-15 have 120°x10° boxed zone and takes ap to several seconds to scan it).

[D-Scythe]

Han, right now, if I shoot an AIM-120 in "Visual", it instantly starts tracking the closest target (no scan-zone delay). If I shoot an AIM-120 normally (locking with my radar first), and the AIM-120 is decoyed by chaff, it takes a long time to reacquire its target (there is a scan-zone delay).

 

Why is that? If an active radar missile like the AIM-120/R-77 tries to re-lock its target (after being decoyed by chaff), it wouldn't scan its full cone, 120 degree search because the target is more or less in front of it. If it was fired in "Visual" Mode, then yeah, I would expect it to take some time to find a target. If it is decoyed by chaff, then it already knows the general volume of airspace to look, so can adjust its scan-zone accordingly - make the radar 'cone' smaller.

 

It should still take some time, but the whole re-locking process should be faster than an AIM-120 in Visual (or an R-77 in missile over-ride).

 

I don't think it makes much sense to have an AIM-120 fired in Visual mode pick up its target faster than one that is decoyed by chaff and is attempting to reacquire its target.

[169th_Crusty]

I don't think it makes much sense to have an AIM-120 fired in Visual mode pick up its target faster than one that is decoyed by chaff and is attempting to reacquire its target.

 

I don`t know... but I would imagine that the missile "checks" what`s within

the HUD`s circle (roughly... of course) when the vis mode is enabled... when

it comes off the rail. Then, if no joy... it embarks on a wild scanning hunt:)

[GGTharos]

When launched 'Mad Dog', the 120's seeker is slaved dead ahead; the scan zone is what you see on the HUD.

 

If it doesn't find a target in that zone for some classified amount of time, it does 'some scanning' ... but that 'scanning' is also classified, so its' best to leave it very narrow since we don't know what it really is - the launch mode is really made for hurried shots at targets within the HUD anyway, so there shouldn't be any need for a lot fo scanning.

 

Once locke don a target, the missile has its vector, and it knows WHEN it lost the target if it is blinded or decoyed by chaff; by knowing the initial vector and the time elapsed it can compute a scan zone within which there is a high probability of finding the target - it should scan that, and nothing else.

[D-Scythe]

So, what you are saying, is that reacquistion time should be reduced because the scan zone is also pretty small like Maddog?

[GGTharos]

So, what you are saying, is that reacquistion time should be reduced because the scan zone is also pretty small like Maddog?

 

 

To a reasonable limit at least - the scan zone could be a couple miles across and if the missile's close enough it might be scanning 60 deg to catch it all (but I find this unlikely - basically you need to move the seeker around more to scan the same volume of space as it comes closer, so this only appleis when you are close to the target)