R-27ET right after R-27ER

It would seem so. With the goal of generating the Launch Authorized cue.

 

If that would be so, then bold part would be unnecessary step:

 

Full instrument support in Close-Range Missile Combat is made possible by range

measurements provided by either the Laser Rangefinder or the Radar Aiming Complex

(with the appropriate switch setting-OLS or RADAR-selected).

 

When the Armament Control Panel is operating with incomplete instrument support in

Close-Range Missile Combat (a situation in which the visually acquired target is locked

with the OPTICAL, HELMET, or VERTICAL modes), a range of zero is automatically entered

(the current range arrow points to zero), the missile is automatically issued R(ange)=0,

and the Armament Control System is set to the allowed launch range.

 

When using the R-73E missile with incomplete instrument support in Close-Range

Missile Combat, the Armament Control System may issue the instruction НОП (Invalid

Targeting Error). When this occurs, the Launch Authorized symbol on the HUD will flash or, if

using the Helmet Aiming System, its aiming rings and crosshairs will flash alternately. Fly the

aircraft in a way which removes the error.

 

Given the presence of an invalid targeting error, an R-73E missile can still be launched.

However, in doing so, the likelihood of hitting the target is reduced.

 

In Short-range Missile Combat you can also enter the range manually using the method

stated above.

 

The range value of 0 is transmitted to missile when the system can not find the range.

If the missile would never be able receive any information for the range then there is no reason to issue such information to missile.

 

It would go similar how Cmptohocah understood it (slight chanes)

 

Airplane: hey "T" do you see that target over there?

R-27T: yup, I see it with my own eye.

Airplane: ok, let me check the launch authorization for you... you are good to go!

R-27T: thanks for your help, I will see you latter!

 

As if there is no where range issued to missile in that, as it would be purely just "GO or NO-GO" situation where missile is simply maintaining a lock and waiting a command for launch.

 

But if we follow that translation of the manual, it would be this:

 

Airplane: hey "T" do you see that target over there?

R-27T: yup, I see it with my own eye.

Airplane: ok, let me check the range for you... target range is not found, assume the range to target is 0 meters. You are good to go!

R-27T: thanks for your information!

 

If the range information would be available, then scenario could be next kind:

 

Airplane: hey "T" do you see that target over there?

R-27T: yup, I see it with my own eye.

Airplane: ok, let me check the range for you... target range is 9000 meters.

R-27T: thanks for your information!

 

How would a information of the target range help the missile?

How would a missile behave differently if it doesn't know a range?

 

• Could it be used to time when to activate proximity fuse?
  
• To be used to optimize the guidance?
  
• Optimize the control fins movements?
  
• Be used to minimize the electricity consumption?
  
• To be used in the Counter-Counter-Measurements systems?
  

 

При отсутствии текущей или введённой вручную дельности в ДРБ при ведущем канале ОЭПС и при включённом выключателе ПР АВТ-РУЧ в положение РУЧ снижается вероятность поражения цели.

ППО в БМБ обеспечивается наличием замеренной дельности ЛД или РЛПК (при включённых соответствующих выключателях ЛД и ИЗЛ).

При работе СУВ в режиме НПО в БМБ (захват визуально видимой цели из режимов ОПТИКА, ШЛЕМ, ВЕРТИКАЛЬ) предусмотрен автоматический ввод нулевого значения дальности (стрелка текущей дальности стоит на нуле), на ракету автоматически выдаётся Д = 2 км и в СУО выдаётся разрешённая дальность пуска.

При применении ракет Р-73Э в режиме НПО в БМБ в СУВ может формироваться команда НОП (недопустимая ошибка прицеливания), на экране ИЛС начинает мигать символ ПР, а в НСЦ мигают прицельные кольца и перекрестие в противофазе. Пилотированием устранить ошибку прицеливания.

При наличии НОП можно пускать ракету Р-73Э, однако при этом снижается вероятность поражения цели.

В БМБ также можно ввести дальность вручную способом, указанным выше.

 

So why is the missile issued automatically range of 2 km to target, if it is not required at all? If it is just the targeting system function to create LA, then there is no purpose to tell missile that range is 2 km and inform pilot that range is unknown by flashing HMD and LA on the HUD and have range arrow at scale at zero, as of course the pilot knows in the close combat mode that target is close as it can be seen? What does the pilot care about lack of range data to the target if only missile seeker lock-on is required and solid tone is received? Why the probability to hit a target gets smaller, and why it is possible to set the range data manually if it is not required to get LA?

 

If we compare this to SAM systems, there is a big difference when you can not receive the range data but you know its direction. You can enter manually the target range for estimation, but it is not required for the launch. The missile guidance methods can be changed a lot when the range is unknown, as well its warhead safety features, flight limitations and warhead fuse are changed to different profiles.

 

So it is just interesting that what makes the Air-to-Air missiles like R-27T/ET and R-73 such that they wouldn't benefit at all by the target range information when every other missile basically does.

You are not reading this correctly.

 

Why I am asking you.

 

So there is no magic stealth BVR capability involved and in regards to R-27R deployment, the only difference between cooperative mode and the normal procedure is that you can "prep" the radar with EOS angular coordinates, but as soon as you launch the missile, the radar kicks in to provide the missile with course corrections and target illumination.

 

So simply put, the IRST is used to scan the volume for targets, and radar is used periodically just to "ping" for the range, making the fighter stay "hidden" (more like mysterious) in the enemy RWR, until actual launch is performed and then it is "all-in"?

 

It only receives course corrections(datalink) when the radar is operating and only for a portion of the flight, which BTW is limited to some 25 km from the launching aircraft - it does not react to datalink corrections once it has the target acquired by itself.....there is a reason why the missile has an onboard seekerhead.

 

Was it a range limited or time limited?

Yes, the reason is that the missile will have more accurate target position to get inside proximity fuse range to trigger explosion. At lower altitudes the missile needs to be closer to target, at higher altitudes it can be further from target as Pk is higher.

All missiles are super simple in their principles. They have one task, and one task only. To get close to the target and blow-up. A missile having wrong attitude on target is a miss. Blowing up at wrong moment is a miss. Being at wrong distance is a miss.

 

The IRST cannot guide anything - it dosen't emit anything....thats why its "stealthy". As the helmet sight, its meant for cueing IR missile seekers with angular target coordiantes as an alternative to radar cueing.

 

I didn't say it emits anything, only that what the real manual says that it is the primary sensor to do the guidance where radar is the transmitter. Something to know where something else, is delivering the guidance information to the missile regardless is another sensor used to transmit those guidance orders. (Analog: You can be blind, but I can still tell you what I see and you can yell it to someone else to operate by commands that I told you.)

 

Nonsense - aside from the hogwash about the IRST guiding the missile,

 

It is your hogwash to assume so.

But lets it pass....

 

the fact is that the R-27R itself is only suseptable to chaff when the SARH seeker is operating and acquiring the target - at which point its no longer under datalink guidance.

 

Wouldn't that as well mean that the seeker is incapable for comparing the radar emissions and the echoes from the target? As it doesn't anymore use the rearward antennas for anything?

As that is just one of the most idiotic things the russian engineers did, on the moment when the missile is under the heaviest CM/ECM, it is denied from all the assistance it could have to know where the target is, so the missile could have a easier time to separate false targets from correct one. (analog: You send someone to large store pick up something, you give accurate information how to get to doors of the store so they don't get lost between you and the store, but then you just say they are on their own to find it inside the huge store.)

 

The point in the "combo" is to have two different sensors on target, so that if the primary one looses lock, the secondary one can take over - if your radar gets jammed by ECM the EOS can take over as it won't or if your EOS looses lock due to changing target aspect, clouds the sun or whatever that can interfere with an IR sensor, the radar can take over as it won't be affected by the same things.

 

Yes, that is what I said....

The two sensors are backing up each others, where only one is providing guidance at the time, but only one can be transmitting radio signals and one invisible light (laser ranging).

Yes you’re right.

 

I have right to ask questions, that's all.

 

Something that make me worry is the R-27ET with 40% less flight performance than his brother R-27ER. When you read official description of both missile you will see about a different of ~5% more in range in favor ER version. Let’s add another 15% less for ET because the guidance is different. That is a total about 20% less range. What we are getting in a combat starting launches from 35km is about 40% less energy in range for ET. The difference is too big. Every weakness you find in description for everything you will find in game twice. And then we must see people coming here telling something is a fact en bla bla bla.

 

If we take a 8 year old kid and we lay down on the table some tools with elementary parts of the missile weapon system. That kid will come up with major clever things what to do with them.

Parts would be like a:

 

- Radio communication (8 year old knows what a walkie-talkie is and how to use it)

- Binoculars (8 year old knows what to do with them)

- Flashlight (8 year old knows what to do with them)

- Reflector tape (8 year old knows what it does)

- Laser/Sonar Ranging device (8 year old knows what it does compared to measurement tape)

 

And you play a simple game with them with a few scenarios.

 

One of the first thins they will very quickly come up, is a scenario where they can guide a 4 year old to a further distance in the darkness, and help them to find something in there darkness.

 

These scenarios can be easily built and made and they will find a solution for a fairly complex tasks without help.

 

We can go back 50 years and only some of those ain't there available for children, like radiotelephone and laser/sonar ranging device. Get 30 years back and radiotelephone is available but not the laser/sonar ranging device. Get 10-20 years back and those became available as well.

 

Now, the children today can come up with extremely clever solutions what comes to problem solving. But that is because difference to previous generation is only availability of the examples that what they do have.

 

As there is is hue difference in 1 + 2 = 3 when you know what a 1 and 2 are, but if you would first need to find out what is needed to 3, it becomes more challenging. Most small kids can solve problems like x + 2 = 3 or 1 + y = 4, when you present the problem in practice. If you just ask them verbally or you ask wrong question then they likely get confused as they don't understand the question.

 

We can take the challenges like the "How to maximize a BVR missile with IR seeker performance at long distance" and kids would come with a far more creative solutions than any missile engineer that are presented here. The difference is just that the kids do not know how to make it happen with computers, electronics and physically.

 

If we split these challenges to practical examples, it becomes obvious that who ever designed R-27T/ET missile, didn't know what they were doing.

But when we have people who just shouldn't be doing what they are doing in their profession, it just doesn't amaze me that military weapons industry is has so many idiots.

 

Like who would be so stupid to use a radio to guide a IR-missile to further distance to find a target that it can't otherwise see from such a distance?

Who would be so stupid lie to enemy that you are guiding a radar missile while it is a IR-missile?

So the whole point of the eventually raised questions "Does R-27T/ET have a data-link?" is not about really that does it or not, but "Why didn't the Soviet engineers think about that?".

 

But as reality is what it is, it becomes quickly something that "it just is so", and eventually some things are even covered by laws "Do not question about this!", and majority will simply accept it, without ever questioning about it as "it must be true as it is said so".

As if there is no where range issued to missile in that, as it would be purely just "GO or NO-GO" situation where missile is simply maintaining a lock and waiting a command for launch.

 

But if we follow that translation of the manual, it would be this:

 

Airplane: hey "T" do you see that target over there?

R-27T: yup, I see it with my own eye.

Airplane: ok, let me check the range for you... target range is not found, assume the range to target is 0 meters. You are good to go!

R-27T: thanks for your information!

 

If the range information would be available, then scenario could be next kind:

 

Airplane: hey "T" do you see that target over there?

R-27T: yup, I see it with my own eye.

Airplane: ok, let me check the range for you... target range is 9000 meters.

R-27T: thanks for your information!

 

How would a information of the target range help the missile?

How would a missile behave differently if it doesn't know a range?

 

Yes, the missiles, even IR missiles, use the additional information provided by the aircrafts sensors to adjust their autopilot and guiding behaviours:

 

 

Here is a rough translation:

 

The RKR algorithm generates one-time commands that are transmitted from the fighter to the missile before and after their descent. These commands affect the on-board missile systems to ensure high efficiency in specific combat conditions. The RKR-Algorithm is activated in the RNP (STT)-mode by the command C_a+t.

 

Before the missile missile is launched, its seeker receives the following messages via the coded signal:

1) CLOSE RANGE OPERATION (BD):

This command is issued when the estimated time of flight before the missile hits the target is less than 7 s. The BD-Command is adjusting the parameters of the autopilot.

2) ZPS (rear aspect shot)

3) TARGET TYPE (small, medium, large)

4) LAND (when working over ground)

5) ANGLE OF ATTACK of the aircraft firing the missile

6) ALTITUDE of the shooter, ALTITUDE of the target, ALTITUDE (average)

 

For the R-27P1, the following additional commands are send:

7) HIGH ALTITUDE for targets flying above 20 km

8 ) NUMBER OF THE MISSILE (1 or 2)

9) MANEUVERING TARGET ZONE when the target is flying at or below 15 km altitude AND M>4,

with M = v/a, with v = speed of the missile and

a = 0,295 km/s for targets flying at or above 11 km

a = (0,3402 – 0,00409*target_altitude) km/s for targets flying below 11 km

 

ZPS command is issued when the target is flying below 1 km and the target is in rear aspect.

 

Commands 4, 5, 6 and the speed of the launch aircraft are used adjust the missiles autopilot.

 

For the R-73 missile, the CLOSE RANGE OPERATION, TARGET TYPE and LAND commands are the same as for the R-27 missiles, but the CLOSE RANGE OPERATION command will be issued when the estimated flight time is below 3.5 s.

For the R-73, the following additional commands are send:

1) FULL INSTRUMENTATION

2) MACH-NUMBER of carrier

3) ESTIMATED FINAL APPROACH SPEED of missile and target

4) TARGET DESIGNATION COMMAND

Edited August 23, 2020 by BlackPixxel

Yes, the missiles, even IR missiles, use the additional information provided by the aircrafts sensors to adjust their autopilot and guiding behaviours:

 

It would be odd that the missiles wouldn't be provided with the information from the aircraft that affects to their logic for guidance. It would literally be about first spending effort to collect information about the target and then ignore it by telling missile just "Fly at that heading and find it out yourself".

 

For the R-73 missile, the CLOSE RANGE OPERATION, TARGET TYPE and LAND commands are the same as for the R-27 missiles, but the CLOSE RANGE OPERATION command will be issued when the estimated flight time is below 3.5 s.

 

So wouldn't in the manual stated 2 km range be that 3.5 km?

на ракету автоматически выдаётся Д = 2 км и в СУО выдаётся разрешённая дальность пуска.

 

As 2000 meters in 3.5 seconds is ~570 meters per second, considering that if you are in a turning fight (with a slower speed than 900 km/h = 250 m/s) then it takes time for missile to accelerate and it is constantly accelerating through whole 3.5 seconds, so it needs to know very well that what is target range so it can maximize it interception inside turning envelope, missile very well might need to perform a far higher turning angles than just normal proportional navigation would inform it to do.

 

For the R-73, the following additional commands are send:

1) FULL INSTRUMENTATION

 

What does that mean? Like the coordinates, range, vector?

 

2) MACH-NUMBER of carrier

 

Makes sense.

 

3) ESTIMATED FINAL APPROACH SPEED of missile and target

 

Makes sense, as it helps with the proximity fuse timing and sensitivity and as well missile maneuverability, as well possible use for range information in time.

 

4) TARGET DESIGNATION COMMAND

 

Is this the target size or pointing "that heat signature is your designated target, lock on it"?

It would be odd that the missiles wouldn't be provided with the information from the aircraft that affects to their logic for guidance. It would literally be about first spending effort to collect information about the target and then ignore it by telling missile just "Fly at that heading and find it out yourself".

 

In the case of IRH missiles it likely doesn't affect guidance at all, unless they really want a Vc estimate (which is possible and not likely to change much in the short flight time of an R-73 - but still unnecessary because at short ranges you're always in terminal guidance)

 

As 2000 meters in 3.5 seconds is ~570 meters per second, considering that if you are in a turning fight (with a slower speed than 900 km/h = 250 m/s) then it takes time for missile to accelerate and it is constantly accelerating through whole 3.5 seconds, so it needs to know very well that what is target range so it can maximize it interception inside turning envelope, missile very well might need to perform a far higher turning angles than just normal proportional navigation would inform it to do.

 

I believe PN will deal with this by itself, at short ranges this information is just not necessary The IRH seeker won't give you a Vc input, though an approximate TTG may or may not be useful. What the IRH seeker probably gets over good old pure PN is target acceleration normal to the turn plane, which makes a difference in reducing miss distance.

On the other hand, it wouldn't be the first missile to adjust fuze activation time and fin deflection parameters when this information is available - but it's likely to be literally a flag of the sort of 'allow toque level 1 until TTG is this much' and/or 'arm fuze' and/or 'restrict aoa to blah' etc.

 

What does that mean? Like the coordinates, range, vector?

 

Makes sense.

 

Makes sense, as it helps with the proximity fuse timing and sensitivity and as well missile maneuverability, as well possible use for range information in time.

 

Vc can be directly input into PN. It just may not be that useful at short ranges, but if you're shooting a bit further then it may make a bit of a difference. The further you shoot, the less useful it becomes vs a maneuvering target.

 

But that has me curious now and if I find the time I'll check some calculations to see if it really would be as ineffectual at short ranges (compared to normal acceleration) as I believe.

 

Is this the target size or pointing "that heat signature is your designated target, lock on it"?

 

Literally point the seeker in this direction, attempt to lock onto whatever you see. Just being pedantic because I seriously doubt there's a 'heat signature' in the language the WCS and the missile are speaking - it's just pointing commands.

In the case of IRH missiles it likely doesn't affect guidance at all, unless they really want a Vc estimate (which is possible and not likely to change much in the short flight time of an R-73 - but still unnecessary because at short ranges you're always in terminal guidance)

 

The parts of the MiG-29B document say that some of the information is used to adjust the autopilot, and it includes infrared missiles.

 

(close range flag, altitudes, for the R-73 additional information is used)

 

What do you mean with Vc? Closure speed?

Yes. Vc is input into PN. You have a basic PN equation, then PN + Vc (used since the 50's sparrows were around), and Pn + normal acceleration, PN + Vc + Normal acceleration.

 

Then you get into even more terms added etc but they're not useful to this discussion - basically, the IRH seeker cannot measure Vc. You can provide this information to the missile initially and it can be input into PN, but the longer you go, the less useful this information can become.

It can also be updated via datalink, as well as computed indirectly from other inputs - but generally, having accurate Vc is the domain of RF seekers. You can also jam Vc (provide false Vc) and send the missile somewhere else - this indicates how important it is to have it accurate.

 

So yes, having range and Vc to set flags is a thing and it's common (again here my surprise for R-27 not having this capability as per Chizh, when AIM-7E was doing this already) so you can set fuze timing, fuze arming, and adjust the autopilot for altitude as the amount of toque you need to apply to achieve commanded acceleration may change with air pressure. The LAND signal is important and I'm happy to see it, as I suspect it would do this (but it may do less than this:)

 

1) De-sensitize the fuze a bit to help dealing with a low altitude target

2) bias the PN in the vertical axis to keep the target slightly below, or, on the horizon if the target dives instead of a 50g PN turn into the ground.

Do not listen to Chizh here, as the R-27 does have the close range flag (when estimated flight time is less than 7s). Also don't listen to him when he says that there is no variable PN, as it has variable PN during the radio corrected stage.

 

Here is a text about the R-27 from a vympel chief designer:

https://forums.eagle.ru/showpost.php?p=265862&postcount=117

 

It says:

"In some cases, corrections are introduced into the guidance law applicable to the radar-guided missiles to optimize their flight trajectories for best performance of the radar homing head and proximity fuse. For example, to avoid a stream of clutter by taking the missile out of the aircraft radar's primary beam or provide for a diving attack on the target at a preset angle."

 

This sounds like what you described. The missile could dive on the target, thus avoiding hitting the ground or getting false fuzing.

 

The R-27R guidance is described as "modified PN guidance with offset".

In the final homing stage it uses closure speed + angular speed of the seeker, as well as the difference between angular rate of the seeker and angular rate of the missile (which is the part of the angular rate that is only caused by the targets movements.).

 

The calculation for a certain axis looks like this:

output = coeff * (closure_speed * angular_rate + filter * missile_speed_projected_on_LOS_vector * delta_angular_rate)

 

I think this is what you described as PN + Vc + normal acceleration, as the delta_angular_rate is only introduced when the target starts accelerating in a direction orthogonal to the LOS vector. If it does not accelerate, delta_angular_rate will be close to zero.

Edited August 23, 2020 by BlackPixxel

Do not listen to Chizh here, as the R-27 does have the close range flag (when estimated flight time is less than 7s). Also don't listen to him when he says that there is no variable PN, as it has variable PN during the radio corrected stage.

 

That's fine, and you've found new information which is great (where did you find it? I can't read Russian so I cannot search in Russian).

Chizh is the most important person to convince about these things here. So just saying, word things in terms of facts and nothing else.

 

This sounds like what you described. The missile could dive on the target, thus avoiding hitting the ground or getting false fuzing.

 

I wouldn't go that far, but this isn't important at this time - the fact is that low altitude flight for missiles and avoiding flying into the ground has been around in some form since the 50s. I would imagine it's part of the basic guidance package for anything that isn't particularly cheap.

 

The R-27R guidance is described as "modified PN guidance with offset".

In the final homing stage it uses closure speed + angular speed of the seeker, as well as the difference between angular rate of the seeker and angular rate of the missile (which is the part of the angular rate that is only caused by the targets movements.)

 

The calculation for a certain axis looks like this:

output = coeff * (closure_speed * angular_rate + filter * missile_speed_projected_on_LOS_vector * delta_angular_rate)

 

I think this is what you described as PN + Vc + normal acceleration, as the delta_angular_rate is only introduced when the target starts accelerating in a direction orthogonal to the LOS vector. If it does not accelerate, delta_angular_rate will be close to zero.

 

Yes, and this is the basic PN package for any RF missile. IRH will probably lack any good Vc, but there are still things you can do with an estimated TTG (in other words, initial Vc and range input by the WCS would be used to calculate TTG and use this to set fuze arm, fin-restriction timing etc ... it would be less efficient that a constant Vc and range input but more efficient than not having them at all, but only for longer ranges IMHO - at short ranges it may help bias the autopilot at launch while PN is still unstable, to achieve the required commanded acceleration with less noise) - again still IMHO.

 

Basically I don't think an IRH missile at short range really needs those inputs, but there is the possibility that they aid in the initial steering at launch, especially for HOBS applications.

 

Having said that, we don't know what the inputs are in DCS ...

 

Anyway, the whole APN package together with axis biasing for altitude etc, should be basically available to all RF missile in DCS. The APN package is, the rest, seems not :)

where did you find it?

 

It is in this document about the MiG-29B

https://www.digitalcombatsimulator.com/en/files/2378427/

 

This document is a treasure, tons of very technical information about the weapon systems of that old MiG-29B

Thanks BlackPixxel, this is indeed a great find.

 

The real difficulty then becomes in a lot of cases, how to simulate all-analogue systems disadvantages vs digital systems.

Why I am asking you.

 

So simply put, the IRST is used to scan the volume for targets, and radar is used periodically just to "ping" for the range, making the fighter stay "hidden" (more like mysterious) in the enemy RWR, until actual launch is performed and then it is "all-in"?

 

Yes pretty much so :) . You can also opt to use the laser rangefinder instead of the radar, but its range is limited to some 6-8 km(IIRC) so only useful for very close encounters.

 

Was it a range limited or time limited?

Both - IIRC datalink limitation is described as "up to 25 km from launching aircraft and 30 seconds of duration"

 

Yes, the reason is that the missile will have more accurate target position to get inside proximity fuse range to trigger explosion.

Well the seeker provides more up-to-date target information and thus provides for quicker reaction to target manoevering when the missile needs it - i.e. when closing in on it at terminal stage.

 

At lower altitudes the missile needs to be closer to target, at higher altitudes it can be further from target as Pk is higher.

All missiles are super simple in their principles. They have one task, and one task only. To get close to the target and blow-up. A missile having wrong attitude on target is a miss. Blowing up at wrong moment is a miss. Being at wrong distance is a miss.

Essentially yes, but detonation of the warhead is down to the fuzes - the R-27 has both radio proximity- and impact fuzes, so in order to "blow up" either one or the other must be triggered....IIRC the proximity fuze of the R-27 has a detonation range of some 11 meters.

 

I didn't say it emits anything, only that what the real manual says that it is the primary sensor to do the guidance where radar is the transmitter.

Ok but I think you mistranslated the "guidance" bit though :) . Its the primary sensor for target tracking - providing the angular target coordiantes to the radar in order to cue it to look in the right direction.....otherwise how would it be able to "ping" it for range information? :) . Also at the point of missile launch, the transition from IRST to radar target tracking/missile support would take longer if the radar hadn't already been "prepped" with the target coordinates.

 

Something to know where something else, is delivering the guidance information to the missile regardless is another sensor used to transmit those guidance orders. (Analog: You can be blind, but I can still tell you what I see and you can yell it to someone else to operate by commands that I told you.)

Thats true and such a procedure does exist as back-up for some SAM systems - i.e. where optical means are used for target tracking and the radar directors being "slaved" to the angular coordiantes while "pumping out" radar energy for an inflight SARH missile to home on. But again its not meant for "stealthy operation", but merely as a way to deal with ECM - aside from the optical means being range limited(and suceptable to other forms of interference), its also less accurate and doesn't provide midcourse guidance(just pure SARH).

 

It is your hogwash to assume so.

But lets it pass....

Yeah ok - whatever :D

 

Wouldn't that as well mean that the seeker is incapable for comparing the radar emissions and the echoes from the target? As it doesn't anymore use the rearward antennas for anything?

No - don't confuse a "ready-made" target fix being transmitted(datalink) to the missile INS for the seeker's own SARH operation. The radar stops transmitting course corrections after a portion of the flight, but it obviously continiues to "illuminate" the target for SARH operation.

 

As that is just one of the most idiotic things the russian engineers did, on the moment when the missile is under the heaviest CM/ECM, it is denied from all the assistance it could have to know where the target is, so the missile could have a easier time to separate false targets from correct one.

What about the american engineers then? - they didn't provide their SARH missiles with any datalink at all :) .

Thanks BlackPixxel, this is indeed a great find.

 

The real difficulty then becomes in a lot of cases, how to simulate all-analogue systems disadvantages vs digital systems.

 

Also keep in mind there were some advantage of late analogue systems vs early digital systems, so it is not clear-cut digital > analogue.

I would say things went digital because of overwhelming advantages.

No - don't confuse a "ready-made" target fix being transmitted(datalink) to the missile INS for the seeker's own SARH operation. The radar stops transmitting course corrections after a portion of the flight, but it obviously continiues to "illuminate" the target for SARH operation.

 

That "radar stops transmitting" would mean only time based part, so after 30 seconds it should stop doing so....?

There is as well some mentions that R-27 battery is guaranteed to provide power for 30 seconds for seeker functionality after it is activated. Meaning the said 60 second limit would be 30 + 30 seconds where 30 seconds it is completely blind and power is used minimal manner, and after 30 seconds when the SARH seeker is activated, it has 30 seconds operation time to find the target, as no more there is any guidance for further time. In 30 seconds time at 14 000 meter altitude and Mach 1.8 launch speed the R-27ER has managed to fly only ~37 kilometres (air distance). At that moment it would be killed by the guidance of the datalink by time, or if by the distance of 25 kilometres then about 19 seconds after the launch.

Against a Mach 1.8 Head-On target at the same altitude there is either ~30 km distance to find the target with the SARH seeker only, or ~12-13 seconds before interception. If the target does make any maneuver (ie. Mach 1.8 to 1.0 and ~35 degree angle chance) while still maintaining guidance , then time for intercept after datalink is cut becomes almost 22 seconds, or 30 kilometres.

 

So what would a SARH do after 25 km or 30 seconds when it can not find the target?

 

What about the american engineers then? - they didn't provide their SARH missiles with any datalink at all :) .

 

Didn't the AIM-7MH receive one? And AIM-120 was needed upgrade for medium range missile features.

But that comes again that why did Soviets/Russian stop updating a R-27 missile that is 37 years old now (and still in active use) if it was so bad? Meanwhile lots of new other missiles improved, new missiles designed for other purposes etc...

 

And one interesting part of all discussions that comes about R-27 modularity is this:

 

 

Followed by the link that was just above posted, quotation from there:

 

A unified missile system was developed. It could use missiles of two weight versions and featured a high degree of commonality of components (control section, warhead, structural elements, and fixed and control surfaces). However, the missiles are equipped with different propulsors (basic version, designated R-27; and high-power version, designated R-27E). The latter's launch weight exceeds that of the basic version 1.4 times.

 

In addition, both versions are equipped with interchangeable homing head modules: semi-active radar homing head and passive IR homing head. Use of the missiles equipped with different homing head types increases the probability of hitting a target.

 

The modular design of the R-27 missile has made it possible to develop a system with unique performance characteristics having no analogs in Russia or abroad. Owing to the system's modular design, its considerable modernization potentialities can easily be utilized to improve design and performance characteristics by 25 to 30 percent.

 

(if there is potential to update something, it doesn't mean so has been done....)

 

– the missile equipped with a radar homing head uses a combined guidance method which makes it possible to fully exploit the missile's ballistic capabilities which exceed the homing head's target acquisition range 2 or 2.5 times. In the initial phase, the missile uses inertial guidance to head for a calculated target position. The target position and speed data are then corrected via a data link. In the terminal phase, after locking on the target, the missile is controlled by the homing head;

 

So 30 + 30 seconds sounds about it for 2-2.5x distance?

Does the 25 km sound about it? About a 50-75 km (air distance)?

And while the missile is controlled by the seeker, does it 100% sure mean that no other assistance is accepted anymore?

 

But then comes the above picture related text:

 

A unified missile system was developed. It could use missiles of two weight versions and featured a high degree of commonality of components (control section, warhead, structural elements, and fixed and control surfaces). However, the missiles are equipped with different propulsors (basic version, designated R-27; and high-power version, designated R-27E). The latter's launch weight exceeds that of the basic version 1.4 times.

 

In addition, both versions are equipped with interchangeable homing head modules: semi-active radar homing head and passive IR homing head. Use of the missiles equipped with different homing head types increases the probability of hitting a target.

 

Now, does anyone notice anything odd in those?

 

Edit:

 

As addition:

 

 

1. CNS;
   
2. radar detonator;
   
3. autopilot;
   
4. steering linkage;
   
5. hydraulic pump;
   
6. turbogenerator;
   
7. gas generator;
   
8. PIM;
   
9. combat unit;
   
10. engine.
    

Edited August 23, 2020 by Fri13

I would say things went digital because of overwhelming advantages.

 

Absolutely, weight and processing power being major ones, but early solid-state electronics were prone to overheating and other reliability issue.

It is not 30 second of seeker operation time, it is 30 seconds of inertial navigation time, maybe because afterwards the error would get to large.

 

From what I understand from the MiG-29B document the radar can do either datalink or semiactive homing pulses for each of the two missiles it can support.

The datalink is sent in exactly the same time frames where the homing pulses will be send. So it is either one or the other. Each of the two suported missiles has its own time frame tho.

The aircraft will estimate when the missile is somewhere around seeker range from the target (10, 25 or 40 km depending on target size set by the pilot) and switch from datalink to homing.

(this could also mean that the target should only get a launch warning when the missile is within about 25 km from it)

 

As the missile is only powered for the first few seconds of the flight, it will travel most of its distance in the first 30 s of the flight. By that time I think it is guaranteed to be within 25 km from the target.

 

Edited August 23, 2020 by BlackPixxel

It is not 30 second of seeker operation time, it is 30 seconds of inertial navigation time, maybe because afterwards the error would get to large.

 

That is a good point. But how big error would be unacceptable for the INS to get it close enough for seeker to take a control?

Can't a INS be updated later with the seeker? As you don't need to have a high accuracy for 30 + seconds, just for shorter time periods between updates? If you know that X has a steering error of 0.yz degrees per minute, you can still use it with updated corrections between too high error periods.

 

Still considering that if the R-27 missiles are battery limited by the 60 seconds, that 30 seconds has something to do with that. Like, what would happen if hypothetically we would have a battery time of 120-180 seconds but everything else would be status quo? There would be huge cap between launch point and range where seeker would have any possibilities to detect a target...

 

From what I understand from the MiG-29B document the radar can do either datalink or semiactive homing pulses for each of the two missiles it can support.

 

So to guidance channels and both are either in datalink mode or active SARH guidance mode.

But it can't be datalink + SARH same time?

 

The datalink is sent in exactly the same time frames where the homing pulses will be send. So it is either one or the other. Each of the two suported missiles has its own time frame tho.

 

Okay, so it should be possible to have a one missile in datalink guidance while other is already in SARH guidance.

 

The aircraft will estimate when the missile is somewhere around seeker range from the target (10, 25 or 40 km depending on target size set by the pilot) and switch from datalink to homing.

 

That makes more sense and use for the target size adjustment knob (btw, do you happen to know is that size knob in the Su-27 a linear knob, or position knob? As in western fighters one selects [small]-[medium]-[large] but in Su-27 it looks to be a "volume knob" that has no steps in it).

 

(this could also mean that the target should only get a launch warning when the missile is within about 25 km from it)

 

Shouldn't the datalink be just an extra instead a replaced signal?

As the datalink then should be always SARH+datalink and 30 seconds later datalink is just dropped and SARH is left....

 

It is just odd that if so, SARH is always just wasted until datalink is to be dropped, and then datalink is wasted after only SARH would be used.

 

It would make a sense to work similar as some SAM systems where you can keep the target unlocked until missile reach terminal phase where you will lock the target and command the missile SARH seeker to activate (or if missile is without SARH seeker, just lock on for accurate position and guide missiles in). The target does receive the lock signal only in terminal phase in such a way, but you are guiding missiles at target with lower accuracy and likely miss if they do change vector/speed too much.

 

But we should know that it doesn't work that way in...

 

As the missile is only powered for the first few seconds of the flight, it will travel most of its distance in the first 30 s of the flight. By that time I think it is guaranteed to be within 25 km from the target.

 

That takes us back to the idea to launch R-27T/ET first and then R/ER. But if one launches first the R/ER, then it is needed to wait the rocket motor shut off, missile steer away from line of sight etc.

 

 

Sad that we do not have that "two R-27 against two targets" capability in the Su-27S N001 radar as it lacks the another guidance channel AFAIK.

 

 

But based to that the 30 seconds is time the missile would have any means at maximum possible scenario reach 25 kilometres.

 

Mach 1.8, 14000 metres launch gives already a flight range (air distance) about 37 km, while 25 km range is at about 19 seconds (about 10 seconds short).

BUT, that is just the air distance and not a "25 km of the carrier".

The R-27ER to be 25 km away from the carrier (considerin that Su-27 keeps Mach 1.8 and 14000 metre tail-chase) is about 34 seconds....

In that 34 seconds time a R-27ER is about 25 kilometres from the Su-27, and the R-27ER has flown about 41 km (air distance).

Yes, one missile can already be in SARH homing while the other one can still be in datalink stage.

 

If a third missile is fired while the first two are still in datalink stage, then there will not be a datalink for the that one. But the aircraft will propably be close to the target already at that point.

 

And for ranges from seeker range to 1.5* seeker range, pure INS will be used without datalink corrections (not required for this small gap).

 

Aircraft with PESA radar (such as Su-30) can guide two R-27 simultaneus at independend targets, because the beam can switch fast enough.

 

 

The knob will be a discrete knob with three positions, there are just small, med and large. They also affect the proximity fuze settings of the missile.

Edited August 23, 2020 by BlackPixxel

Yes, one missile can already be in SARH homing while the other one can still be in datalink stage.

 

If a third missile is fired while the first two are still in datalink stage, then there will not be a datalink for the that one. But the aircraft will propably be close to the target already at that point.

 

Continuing a SAM systems analogy, you have a X number of channels for missile guidance and can't guide more until you free a channel. This was a limitation example in earlier SAM systems where you had just one channel and capability so on guide only one missile at the time. Then upgrades to two channels made possible to guide a two missiles at the same target. And then new upgrades to allow multiple targets tracking with multiple channels, so there became possible example have a two targets with four channels, that made two missiles per target, and then ESA radars made possible to launch all missiles at different targets etc as mechanical radars limitations were removed.

 

So that is a question that what really would happen with a such fighter radar system where you have first missile in terminal guidance, second still in a data-link and reaching a terminal guidance, and third is launched? With a ESA radar that wouldn't be a problem for R-27. But for a mechanically steered it would be a problem, likely the first one would be dropped in the order to guide a third one (that as you say would likely be heading a target at close, so first one is trashed) and it is pilot task to decide the timing of launches so a missile that is in terminal phase is not wasted.

 

Our Su-27S is very limited in the context as you have just a one missile per one target guidance capability, why one can not perform the multiple launches timely and keep target saturated through whole engagement range until closer range. This similar reason likely could as well affect that you shouldn't be able to guide a R-27R/ER and then launch a R-27T/ET afterwards as it would scratch the channel. Similar way how to switch the missile type from R/ER to T/ET between the guidance is little odd. But, there are evidence in the Su-27SK real manual for target sharing and multi-launches against a same target where two are simultaneously launched if launching set to pairs.

 

The control system of the R-27 missile, in addition to the seeker, includes an inertial navigation subsystem with radio correction. In the initial section of the trajectory, inertial guidance is applied to the "mathematical" target with radio correction of its position and speed during target maneuvering (according to information from the carrier transmitted over the radio link). Target designation can be carried out from on-board radar, thermal direction finding or optical-electronic sights of the carrier aircraft, from the pilot's helmet-mounted system. It is possible to launch a missile towards an enemy aircraft with subsequent autonomous capture in flight. When a target is captured by the carrier's information system, an angular target designation is issued to the missile. When the target hits the coordinator's field of view, the missile captures and auto-tracking the target. In the absence of information from the carrier, the rocket is provided for autonomous operation, which is installed by the pilot from the cockpit. Along with the main flight option with the implementation of the proportional navigation method, special guidance modes can be used, providing more favorable operating modes for the seeker and the radio fuse.

https://missilery.info/missile/p27

 

В систему управления ракеты Р-27 помимо ГСН входит инерциальная навигационная подсистема с радиокоррекцией. На начальном участке траектории применяется инерциальное наведение на «математическую» цель с радиокоррекцией ее положения и скорости при маневре цели (по информации с носителя, передаваемой по радиолинии). Целеуказание может осуществляться от бортовых радиолокационных, теплопеленгационных или оптико-электронных прицелов самолёта-носителя, от нашлемной системы лётчика. Возможен пуск ракеты в сторону самолёта противника с последующим автономным захватом в полёте. При захвате цели информационной системой носите­ля на ракету выдается угловое целеуказание. При попа­дании цели в поле зрения координатора ракета осуществ­ляет захват и автосопровождение цели. При отсутствии информации с борта носителя предусмотрена работа ра­кеты в автономном режиме, который устанавливается летчиком из кабины. Наряду с основным вариантом полета с реализацией метода пропорциональной навигации могут применяться особые режимы наведения, обеспечивающие более благоприятные режимы работы ГСН и радиовзрывателя.

 

And for ranges from seeker range to 1.5* seeker range, pure INS will be used without datalink corrections (not required for this small gap).

 

That is more challenging to believe as closer you get the missile at the target then more precise and faster target updates are required. This is why we can guide a missile to long distance without any guidance as you just need to get the missile "in the ballpark/basket", but while missile is in the INS guidance without datalink, it can not perform any corrections related to the target vector/speed changes.

Considering that we would have a missile closing a target that is (or isn't) aware of the coming missile, they can avoid that missile kinetically easily. Timing would be critical, but so would the missile capability perform change in vector for interception.

 

 

Aircraft with PESA radar (such as Su-30) can guide two R-27 simultaneus at independend targets, because the beam can switch fast enough.

 

Exactly. But ESA is not required if you have targets close enough or laterally separated as a mechanically steered radar can still perform guidance for two missiles, this example with a N001VE and N010 "Zhuk" that are capable for guidance of two R-27R/ER at different targets and track IIRC 8-10 targets same time, or four R-77 missiles.

 

The knob will be a discrete knob with three positions, there are just small, med and large. They also affect the proximity fuze settings of the missile.

 

Okay. You are right. I looked wrong at first as it clearly has "S, M, L" letters on it in 8-12-4 clock positions.

 

Edit:

 

About the data-link | SARH phases: https://www.secretprojects.co.uk/threads/r-23-r-24-r-27-aam.60/

 

Regarding SARH:

Talking about the predecessor (R-23R/R-24R), also having a mono-pulse seeker with four receivers in the antenna, you have a fifth receiver directed backwards receiving the "original" signal from the aircraft's radar. This signal was used as reference to compare the phase, enabling the extraction of the doppler shift.

 

Meaning, it wouldn't be used just for the datalink but through SARH guidance phase all way up to the target to receive that Doppler shift information.

It would explain why you would have only a INS + radio correction in initial phase, and then switch to SARH guidance without datalink.

Edited August 24, 2020 by Fri13

That "radar stops transmitting" would mean only time based part, so after 30 seconds it should stop doing so....?

 

Not sure what you mean - the 25 km/30 sec limitation concerns the radio corrected portion of the flight. Basically what BlackPixxel said, although I don't think he is correct about the 30 seconds being a limitation to the INS operation as such(if thats what he meant) - AFAIK the INS is used throughout, but just fed with target information directly from the onboard radar seeker instead of the remotely transmitted one at terminal stage(SARH homing) - if there is a gap between them(radar seeker not yet having acquired the target by the time radio correction is exceeded), the INS will just continiue navigating on the last known target coordinates.

 

There is as well some mentions that R-27 battery is guaranteed to provide power for 30 seconds for seeker functionality after it is activated.

Don't know about that - the only mention I have found concerns the 30 second limitation for radio correction and an overall 60 second limitation for "powered flight", which I interpret as onboard battery time, which in turn doesn't just concern the INS/SARH operation, but also the missile as such.....it also needs power for the autopilot and control surface acutators.

 

Meaning the said 60 second limit would be 30 + 30 seconds where 30 seconds it is completely blind and power is used minimal manner, and after 30 seconds when the SARH seeker is activated, it has 30 seconds operation time to find the target, as no more there is any guidance for further time. In 30 seconds time at 14 000 meter altitude and Mach 1.8 launch speed the R-27ER has managed to fly only ~37 kilometres (air distance). At that moment it would be killed by the guidance of the datalink by time, or if by the distance of 25 kilometres then about 19 seconds after the launch.

Against a Mach 1.8 Head-On target at the same altitude there is either ~30 km distance to find the target with the SARH seeker only, or ~12-13 seconds before interception. If the target does make any maneuver (ie. Mach 1.8 to 1.0 and ~35 degree angle chance) while still maintaining guidance , then time for intercept after datalink is cut becomes almost 22 seconds, or 30 kilometres.

 

So what would a SARH do after 25 km or 30 seconds when it can not find the target?

Miss :D . Well it will continiue on INS navigating on last known target location until the radar seeker finds the target - if it doesn't, its lost.

 

Didn't the AIM-7MH receive one?

No as far as I know the AIM-7M(and sub-variants) got a more modern SARH seeker, but only the AIM-7P got a datalink...and only the last batch of those even.

 

Anyway, the point was that most SARH missiles don't/didn't have datalink and relied on the SARH seeker finding the target by itself shortly after launch. The R-27R was quite unique in having this feature when it was introduced and I suspect it might have had something to do with compensating for an inferior radar seeker technology - at least if you compare the published specs for seeker acquition range of the the R-27R's 9B-1101K and the contemporary AIM-7M, there is a pretty significant difference in favour of the latter.

 

But that comes again that why did Soviets/Russian stop updating a R-27 missile that is 37 years old now (and still in active use) if it was so bad? Meanwhile lots of new other missiles improved, new missiles designed for other purposes etc...

 

I am not sure I understand what you are asking - at some point in the late eighties further R-27 developments were either cancelled(some prospective variants) or put on the backburner, because they had a new more modern design(R-77) in the works. But then came the collapse of the SU, which affected everything. So post-SU, Russia just had to soldier on with whatever they had - a situation that has persisted up until recently. When they started their re-armament programme, they obviously didn't focus their funds on trying to make 40 year old technology relevant for the 21st century. There might be some improvements in store for the "R-27" family as an interim solution until more modern missiles can be inducted in numbers, but it seems to me that most of published intentions for upgrading the R-27 "family" has more to do with Ukrainian manufacturers trying to salvage their production of an outdated weapon.

 

And one interesting part of all discussions that comes about R-27 modularity is this:

 

...So 30 + 30 seconds sounds about it for 2-2.5x distance?

 

Yes it does. If the max seeker acquistion range is some 25 km(against RCS=3m2), then the added INS/radio corrected phase would amount to roughly double the launch range, which is what "2x distance" means :) - also keep in mind that seeker acquisition range is depedant on target RCS. - if its less than the 3m2 specified, then acquisition range drops and accounts for less of the given launch range.

 

Does the 25 km sound about it? About a 50-75 km (air distance)?

Not if you buy the "50 - 75km" launch range as a realistic proposition.

 

And while the missile is controlled by the seeker, does it 100% sure mean that no other assistance is accepted anymore?

What BlackPixxel said - from what I can gather the radar transmits either course corrections or target illumination - i.e. not both at the same time. Also the quote you posted yourself is clearly indicating this;

 

In the initial phase, the missile uses inertial guidance to head for a calculated target position. The target position and speed data are then corrected via a data link. In the terminal phase, after locking on the target, the missile is controlled by the homing head

 

Now, does anyone notice anything odd in those?

Nope - whats odd about it?
Edited August 24, 2020 by Seaeagle

Continuing a SAM systems analogy, you have a X number of channels for missile guidance and can't guide more until you free a channel.

 

N001 and N019 have two "channels", which is more like time frames as everything is done time multiplexed by the very same radar. But there is also a third backup time frame. Its use is not explained in the MiG-29B doc.

 

So that is a question that what really would happen with a such fighter radar system where you have first missile in terminal guidance, second still in a data-link and reaching a terminal guidance, and third is launched?

 

Su-27SK manual is very clear:

 

5.6.4. После схода 2-х ракет с РГС в режиме ОДИН (двух серий в режиме ЧАСТЬ), пущенных по одной цели двумя нажатиями гашетки П, в зависимости от условий пуска, символ ДР может скачком переместиться на меньшую дальность, максимально, примерно, на 0,5 первоначальной дальности. Если осуществлять пуск третьей ракеты с РГС (до достижения первой ракетой цели), то она пойдет на цель без радиокоррекции.

 

It basically says: When a third missile is launched, it will go towards the target without radio correction.

 

It will of course pick up the SARH homing pulses once the first "channel" switches from radio correction to target illumination. But until then it will be pure INS towards the known intercept point during launch.

 

Our Su-27S is very limited in the context as you have just a one missile per one target guidance capability, why one can not perform the multiple launches timely and keep target saturated through whole engagement range until closer range. This similar reason likely could as well affect that you shouldn't be able to guide a R-27R/ER and then launch a R-27T/ET afterwards as it would scratch the channel. Similar way how to switch the missile type from R/ER to T/ET between the guidance is little odd. But, there are evidence in the Su-27SK real manual for target sharing and multi-launches against a same target where two are simultaneously launched if launching set to pairs.

 

You can engage the target with all your missiles, and launching a heat seeker should not interfer with the radar guided missile operation that is already in the air (why do you think so?).

The only limitation is that only two R-27R/ER can be datalink guided at one target. But this is not really a limitation that will affect you, as you will not fire all of them at once at long range anyway.

 

That is more challenging to believe as closer you get the missile at the target then more precise and faster target updates are required. This is why we can guide a missile to long distance without any guidance as you just need to get the missile "in the ballpark/basket", but while missile is in the INS guidance without datalink, it can not perform any corrections related to the target vector/speed changes.

Considering that we would have a missile closing a target that is (or isn't) aware of the coming missile, they can avoid that missile kinetically easily. Timing would be critical, but so would the missile capability perform change in vector for interception.

 

The early R-33 did not have any radio corrections in the first stage either, it was pure INS.

The R-27R/ER, if launched within this pure INS range, will cover those max of 12,5 km very rapidly, the target itself is also getting closer on its own. Also the missile is launched with information on the targets position and velocity vector during launch, so it will fly along the predicted intercept heading.

 

The pilot seems to have a switch where he can turn radio corrections on and off, not sure if he can force it on for any shot above 25 km? Also, this 1.5*seeker range for pure INS stage is from that MiG-29B doc. It could very well be different for Su-27.

Not sure what you mean - the 25 km/30 sec limitation concerns the radio corrected portion of the flight. Basically what BlackPixxel said, although I don't think he is correct about the 30 seconds being a limitation to the INS operation as such(if thats what he meant) - AFAIK the INS is used throughout, but just fed with target information directly from the onboard radar seeker instead of the remotely transmitted one at terminal stage(SARH homing) - if there is a gap between them(radar seeker not yet having acquired the target by the time radio correction is exceeded), the INS will just continiue navigating on the last known target coordinates.

 

I meant that maybe the INS will start to drift and the coordinate systems of the missile and the launch aircraft, that are the same during launch, will be to far off to still find the target based on the radio correction information reliably.

I meant that maybe the INS will start to drift and the coordinate systems of the missile and the launch aircraft, that are the same during launch, will be to far off to still find the target based on the radio correction information reliably.

 

Ah ok - yes that sounds plausible.