BlackPixxel

I understand that the target sharing process for the Flanker datalink in multiplayer might be a bit out of the scope for FC3, as it would require more than 14 additional buttons and additional data to be sent between the clients over the network. But: Sharing the position of the three wingmen in the group in multiplayer with their number is not. It requires no additional buttons, it requires no additional input by the player, and all the data that is needed is already on the PC of the client: The position and speed of the wingmen and their number in the flight. Do you think it is possible to at least add the position of the 3 wingmen of the flight onto the display in multiplayer? I think that would be a really good compromise that makes all the Flanker fans happy without being a huge workload for ED.

I see, it appears that the radar changes the time intervall for the regular operation as well. In normal single target track, the cycle time is 20,48 ms. In DNP mode, it becomes 51.2 ms. So I agree, the RWR, if it knows the time intervalls, could use this change of the normal radar signal itself to trigger the launch warning.

The homing signal is only emitted when the missile is expected to be 25 km from the enemy fighter. For the radio correction phase for example, the radio correction signal will be sent instead in those 30 ms time slots, as you can see in the second picture.

Maybe, maybe not. In DCS if an F-18 launches an Aim-120 from STT onto another F-18, there will be no launch warning. Should there be one, as the F-18 understands exactly what the datalink signal looks like in this case? Radio correction signal is also much weaker than the guidance signal (range is limited to 25 km distance between launch aircraft and missile).

Here is another important part of the R-27 that should be considered when doing the rework: The SARH homing signal will only be send when the target is expected to be within the allowed seeker range for the selected target size (25 km for a fighter = med sized target). When the missile is in radio correction stage (when it was launched beyond 1.5*seeker range), then, instead of the SARH homing signal, the radar will transmitt the radio correction signal. When the missile was launched between seeker range to 1.5*seeker range, then it will fly with pure INS without correction until it is within seeker range, at which point the SARH homing will begin. It can be expected that the radar will in this case only transfer to SARH signal when according to its own calculation the missile will be within seeker range from the target. So in conclusion: The target should only get a launch warning, when at least one of the R-27R/ER is within a range of 25 km from it. If the closest missile is still beyond that range, there can not be a launch warning, as the radar is not painting the target yet with the SARH signal.

So the launch plattform will send the seeker activation command when it expects the target to be within 25 km from the target, which should mean that under most circumstances this internal timer in the missile should not become 0? And when it is fired from 25 km to 37,5 km, will the seeker activation be send as well?

Is there even a dedicated seeker activation signal? The missile knows the time diagramm of the launch aircrafts radar, and it knows its "channel" (so it either looks for the pulses/radio corrections for channel 1 or channel 2). Maybe it is already enough to simply receive the homing pulses from the correct time channel via its reference antennas to cause its seeker to "wake up". I would think the SARH homing starts before that "timer" in that formula goes down to 0.

Where does it say that 4.3 will only be implemented when the missile is fired between 25 and 37,5 km? First it says that this formula is used when the missile is aimed using INS, and INS is used in both pure INS stage as well as in INS + radio correction (launch from 1.5 to 2.5*lrz). The sentence "If radio correction is used, then the first term in (4.3) will become XYZ" is saying that during the radio corrected phase formula 4.3 with a slight modification is used. And those modifications are just that the speed of the missile projected on the LOS vector is approximated with the closure speed of missile and target. So not a drastic change. And d = lx is not even an approximation, those are identical. This time does not have to be the same timer that the launch aircraft uses when it decides that it will start transmitting SARH pulses. It is just a term to make the navigation coefficient variable with distance, with an arbitrarily factor to avoid the term reaching 0. For the aircraft, it will propably be T=(lx-lrz)/(derivative of lp). Why would you delay the time where the aircraft starts painting by an additional 5 km for no reason by having this 0.8 factor?

Seems good, my terminal condition was the missile being able to hit the target, regardless of its speed.

Please read the first sentence in my third picture. It says that if the radio correction system is used, then the first term in equation 4.3 (which is the one with the variable coefficient) equals another one, where some symbols are replaced with some approximations, but it is essentially similar to the one in 4.3. It is super clear that in the radio correction phase variable PN will be used. And you really think they will allow for the PN coefficient to grow to an infinite value when the missile is still far from the target? It would also mean that the missile would use its seeker only 20 km from the target. So fire at 25 km and seeker goes on directly after launch. Fire at 25.1 km and the missile flies 5.1 km with INS and uses its seeker 20 km from launch. In my opinion, the 0,8 factor is used so the time does NOT reach zero when the missile is 25 km from target, to keep the variable coefficient low.

The seeker, when launched from 25 to 37,5 km, will already point at the estimated target position that it will have when the rocket is estimated to reach 25 km to target. But the missile can be lanched of boresight, and the variable PN during this INS stage will cause the missile to do a smooth instead of a sharp turn. Variable PN will also be used during the radio corrected portion of the flight when the missile is launched beyond 37,5 km, as you can see in the document (Why do you think it would not be used? Just look at the third picture I posted, it is about the radio correction stage). Also, the navigation constant will of course not reach infinity, as the fighter will transition to radar homing when the missile is estimaged to be 25 km from the target. So it will be (25 km - 0.8* 25km), which means the 4 gets divided by 5, not zero.

It just seems so odd with the plane to plane link. It is fully working in singeplayer, all that would be different in multiplayer is that the position and the targets of 3 other players will be taken instead of from AI.

I am not saying that the diagram is an Aim-120B. But isn't the Aim-120B using the same motor and the same shape as the Aim-120A, with the big change of introducing loft? I fired the missile without loft, so the straight line performance should match that of the Aim-120A.

But in DCS the "balance" is artificially made worse by having a very important feature of the Flanker missing, its group datalink, which would certainly be used on the real ones in the scenarios we fly on the multiplayer servers (west vs east). This is a big degradation in the SA and teamplay of the Su-27 pilots.

How comes that the DCS Aim-120B fired WITHOUT loft exceeds its estimated straight line performance by 33% (240 m/s shooter + target) and by 50% (500 m/s shooter + target)? I doubt that the soviet rocket scienists made such huge mistakes?

Thanks!

Chizh, right now the R-27ET has the long safety maneuver time of ~1.5 s, that a missile launched from the catapult launcher would have. Would it be possible to simply give it the same safety maneuver time of ~0.4 s that the R-27T already has? The R-27ET can never be launched from the catapult and will only be launched from the rail launcher, so the 0.4 s would be the correct value here.

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.

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. Su-27SK manual is very clear: 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. 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. 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.

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.

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.

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

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.

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, 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