RWR sound for launch of semi active radar missiles - how and is it realistic?

[darkman222]

I am flying on the "just dogfight" server. They disabled the active radar Amraam missiles. So I am pretty sure when I get fired a radar missile on me its an Aim7 Sparrow. I get the missile warning tone which is nice :) but is it realistic? How does the Hornet know a missile is fired at me? Technically the opponent does an STT lock on me and fires a missile which has no active radar, so nothing changes from the event of being STT locked and the missile being fired on me. I am curious. There is no additional radiation emitted which could trigger the RWR to warn me, right?

Edited February 6, 2020 by darkman222

[randomTOTEN]

Supporting a SARH missile is the not the same thing as performing a STT (to my knowledge). The F/A-18C's RWR can tell the difference.

[Fri13]

Radar starts typically guidance commands transmission on moment missile launches, so emission changes and it reveals launch.

[darkman222]

Well okay. Thanks. That makes sense. So the change of the enemy radar adding guidance commands changes whats the F18 RWR receives. So the RWR switches from "enemy aircraft locking" to enemy "aircraft providing guidance" and that will make it play the "missile launch" sound. Now I understand. Makes total sense now. This is how SAM launches get detected

Edited February 6, 2020 by darkman222

[randomTOTEN]

Wikipedia reports, "Modern SARH systems use continuous-wave radar (CW radar) for guidance. Even though most modern fighter radars are pulse Doppler sets, most have a CW function to guide radar missiles."

 

 

I was under the impression this only applied to older SARH systems, and newer systems use Command Guidance.. but perhaps it's the case that modern systems use a combination of both.

 

 

Regardless, Tracking and Supporting a launch are very different things, with different goals.

[nighthawk2174]

Wikipedia reports, "Modern SARH systems use continuous-wave radar (CW radar) for guidance. Even though most modern fighter radars are pulse Doppler sets, most have a CW function to guide radar missiles."

 

 

I was under the impression this only applied to older SARH systems, and newer systems use Command Guidance.. but perhaps it's the case that modern systems use a combination of both.

 

 

Regardless, Tracking and Supporting a launch are very different things, with different goals.

 

 

Wikipedia is inccorect here, yes older US jets used a CW transimiter. But latter on in US jets and the russians from the 60's either had missiles that home in on a high PRF PD signal (us jets after the F4) or used what's called CWI (Russian jets and flood mode for US). CWI is a PD signal with a really high/low (forgot which word works best) duty cycle.

 

Command guidance was largely used on the older SAM systems I have pics of a good explanation here:

https://forums.eagle.ru/showpost.php?p=4044289&postcount=6

Edited February 6, 2020 by nighthawk2174

[bear.is.flying]

How a modern RWR processes and interprets radar signals is one of the most highly classified of all military secrets. Anyone who knows what they’re actually talking about isn’t going to post about it. Anyone who’s posting doesn’t have any idea what they’re actually talking about. Enjoy your game.

[nighthawk2174]

ehh we know how they work on a basic level, I think there's even a doc out there with the code used on an older one, it isn't exactly a state secret its more the limitations of a particular system or its effectiveness that's classified.

 

 

For example RWR's tell you've been launched on by the change in the PRF when the missile is launched. In order to support the missile you often need a really high PRF. I was just reading the other day that the 23MLA's tracking is 5khz with the missile channel at 100khz. (or mhz forgot if it was mhz or khz). As you can tell there is a dramatic difference in PRF which a rwr would be able to distinguish and then trigger a audible warning in the cockpit.

Edited February 6, 2020 by nighthawk2174

[Banman]

So, if the guidance frequency changes immediately on launch, then why when someone launches on you in TWS mode your RWR does not give a launch warning until the missile goes pitbull?

[NoJoe]

So, if the guidance frequency changes immediately on launch, then why when someone launches on you in TWS mode your RWR does not give a launch warning until the missile goes pitbull?

 

In that case it's because the radar signal doesn't change. Instead, the AMRAAMs use a datalink for mid-course guidance until they get close enough to turn on their onboard radar.

[Bunny Clark]

The specific change that the RWR is looking for is a shift from a Pulse Doppler track mode to Pulse Doppler Illumination, or PDI, which is used for semi-active missile guidance. In the Hornet you can actually see the displayed radar mode change to PDI when you launch a Sparrow. PDI injects missile guidance specific radio pulses into the PD STT transmission that allows the seeker head on the missile to more easily identify the target. The illumination is also coded to the specific launching aircraft, so that the missile only guides on the target being illuminated by the launching aircraft, and not any other aircraft currently being illuminated for guidance (a wingman's target, for example). SARH missiles like the AIM-7 detect PDI energy reflected by the target using their own radar receiver and home in on that. They do not use command guidance, and I'm not aware of any air-to-air missiles that do for terminal guidance.

 

Also, the RWR distinguishes between a radar in search mode vs single target tracking mode by how often the radar sweeps over the plane. A radar that is only hitting the plane once every second or two is in search mode, while a radar that is constantly pointed at the aircraft is in track mode. One of the advantages of TWS radars is the ability to provide some level of weapon guidance while remaining in a search mode and not necessarily tipping off an adversary to a weapon launch.

[darkman222]

So I guess even when you launch an AMRAAM with your radar in RWS mode locking ther target, the enemy would still just continue hearing the "being locked" sound , but no launch sound until the AMRAAM goes pitbull, right? The AMRAAM might be using data link in that case too.

Edited February 7, 2020 by darkman222

[b101uk]

but no launch sound until the AMRAAM goes pitbull, right? The AMRAAM might be using data link in that case too.

 

 

the data-link is an additional emission, the presence of which in conjunction with radar emanating from the same place would itself signify a launch, given the data link doesn't have to be decoded or understood, just the fact it is there at a specific frequency range with a fast enough data rate for corrections.

 

 

 

 

that is why some missiles it can be beneficial to hand-off so the radar track and data link track appear from two different places.

[Bunny Clark]

So I guess even when you launch an AMRAAM with your radar in RWS mode locking ther target, the enemy would still just continue hearing the "being locked" sound , but no launch sound until the AMRAAM goes pitbull, right? The AMRAAM might be using data link in that case too.

 

Not exactly. Technically, RWS cannot support weapon guidance, but when a Hornet launches an AMRAAM in TWS the target aircraft will continue to be alerted to the Hornet radar in search mode only. Unless the Hornet goes STT for the missile launch, the target will never get a lock alert. Once the missile goes active, the alert will be for the missile, and will not indicate the launching aircraft in any way.

 

the data-link is an additional emission, the presence of which in conjunction with radar emanating from the same place would itself signify a launch

 

The ability for a RWR to alert a pilot to an missile in the air receiving mid-course guidance is not something that's modeled in DCS, and not a function that is supported by any publicly available documentation that I'm aware of. That's not to say that RWRs don't have such a capability, since there is a lot about them that is not available publicly nor have I probably read everything that is public.

 

Such a function would have fairly limited usefulness though. For a missile launched in a TWS mode a RWR may be able to detect missile guidance transmissions, but it would have no way of knowing which aircraft is the target. A missile could be launched on you, your wingman, or another flight 40 miles away and you would get such an alert just the same.

 

Having the situational awareness to know when an enemy aircraft is close enough to engage you, and to know when they've committed on you, is far more important. If you're ever surprised by a missile launch against you, you've already lost the situational awareness game badly.

[VpR81]

Once the missile goes active, the alert will be for the missile, and will not indicate the launching aircraft in any way.

 

That is a bit confusing to me. Let me get this together...with RWS the targeted aircraft recieves a launch warning, because the attack radar emissions increase to support the launch/guidance of the missile. simple spoken. Right?

 

But using TWS... what does the missiles radar do as soon as it goes active? I mean in terms of emissions. Are these realy comparable to those of the attack radars guidance mode with RWS? I´d assume, the difference to the attack radars STT is marginal as the missiles radar is less poweful, but then there would not be a missile warning on the RWR. Or am i wrong about this?

Edited February 7, 2020 by VpR81

[GGTharos]

That is a bit confusing to me. Let me get this together...with RWS the targeted aircraft recieves a launch warning, because the attack radar emissions increase to support the launch/guidance of the missile. simple spoken. Right?

 

 

Yep, there's an inserted signal which basically changes the 'tune' so to speak.

 

 

 

But using TWS... what does the missiles radar do as soon as it goes active? I mean in terms of emissions. Are these realy comparable to those of the attack radars guidance mode with RWS? I´d assume, the difference to the attack radars STT is marginal as the missiles radar is less poweful, but then there would not be a missile warning on the RWR. Or am i wrong about this?

 

 

 

The missile radar goes into a search mode, identifies its target and then goes STT on that if it can. There may also be PRF switching etc, but basically it's search then lock.

In DCS it's pretty much just lock, there's no RWR-detectable search phase, even though it does exist in some fashion in-game.

The missile's radar tends to be fairly close to its target so the RWR shouldn't have any trouble picking it up.

[VpR81]

The missile radar goes into a search mode, identifies its target and then goes STT on that if it can. There may also be PRF switching etc, but basically it's search then lock. In DCS it's pretty much just lock, there's no RWR-detectable search phase, even though it does exist in some fashion in-game. The missile's radar tends to be fairly close to its target so the RWR shouldn't have any trouble picking it up.

 

Ok, but that´s exactly what is confusing to me. If the missile goes into a search mode and then switches to STT after going pitbull, the targeted aircraft should recieve only a warning sound for beeing locked, not a missile warning sound as it does in DCS. Shouldn´t it? Or am i still wrong?

 

In this case in RWS, the missile sound on the RWR should turn back into a lock warning only if the motherships radar breaks lock and stops guidance of the missile, as soon as it goes pitbull. Right?

[Harker]

Ok, but that´s exactly what is confusing to me. If the missile goes into a search mode and then switches to STT after going pitbull, the targeted aircraft should recieve only a warning sound for beeing locked, not a missile warning sound as it does in DCS. Shouldn´t it? Or am i still wrong?

 

In this case in RWS, the missile sound on the RWR should turn back into a lock warning only if the motherships radar breaks lock and stops guidance of the missile, as soon as it goes pitbull. Right?

The RWR has an internal database and it compares any received signal against it. For example, the APG-73 II radar of the Hornet produces a different signal than the APG-56(V)5 of the Viper, or the N001 of the Su-27 etc. That's how it can recognize the radar and give feedback to the pilot, in the form of 18, 16 and 29 in the RWR scope, respectively. That database is paired with threat estimation logic and that's how an AWACS search radar will be classed as no threat, while a SAM tracking radar might be classed as a threat, if you're close enough (strong enough signal).

 

If that database contains the AMRAAM's missile radar signature, the RWR will realize that an active missile is locked onto your aircraft. And if an active missile is locked onto your aircraft, that can only mean that it's guiding itself towards you. Thus, the RWR will immediately elevate that radar's threat class to maximum and display it as it would display a launch, in order to warn the pilot.

[randomTOTEN]

 

this is for an older version of modern day RWR's, but obviously describes the basic principles

[Bunny Clark]

Ok, but that´s exactly what is confusing to me. If the missile goes into a search mode and then switches to STT after going pitbull, the targeted aircraft should recieve only a warning sound for beeing locked, not a missile warning sound as it does in DCS. Shouldn´t it? Or am i still wrong?

 

Your confusion is justified, from a purely technical point of view what the AMRAAM's radar is doing is very similar to what an aircraft radar would be doing while acquiring a target in STT. The main reason the RWR treats a missile seaker differently is that it knows it's a missile. Harker nailed it:

 

If that database contains the AMRAAM's missile radar signature, the RWR will realize that an active missile is locked onto your aircraft. And if an active missile is locked onto your aircraft, that can only mean that it's guiding itself towards you. Thus, the RWR will immediately elevate that radar's threat class to maximum and display it as it would display a launch, in order to warn the pilot.

 

To expand a bit - every radar system works a bit differently. They use slightly different radio frequencies, shift frequencies at different speeds, operate on different PRFs, have different beam patterns and scan rates, and different transmission powers. The RWR in a fighter is programmed for all these things, analyses the received radar signal, and compares it to a database to determine what kind of radar system generated the signal.

Edited February 8, 2020 by Bunny Clark

[VpR81]

I knew about the RWR has a database containing radar signatures of different aircrafts, that Su-27 and MiG 29 both show up as 29 on the RWR as they share the same radar and so on... but wasn´t aware it also contains the signatures of onboard missile radars, what is on the other hand somehow logical. Now this makes sense, thanks a lot for clearing that out.

[GGTharos]

I knew about the RWR has a database containing radar signatures of different aircrafts, that Su-27 and MiG 29 both show up as 29 on the RWR as they share the same radar and so on...

 

 

This is actually not correct.

[Bunny Clark]

This is actually not correct.

Yup, the MiG-29 uses the N019 Rubin and the Su-27 uses the N001 Mech. The two radars share a lot of components, but I'm actually a bit skeptical that their transmissions are so similar that modern RWRs cannot tell them apart.

[VpR81]

Realy? So why do they show up both as 29 on the RWR?

[GGTharos]

Because that was the assumption. It was an incorrect assumption.