RWR Warning for ARH missile launches in STT

[dundun92]

First, unsure of the correct channel for this so just stuck it here.

The issue is with RWRs for DCS aircraft (I have tested it in the F-15/16/18, and SPO-15 of the Russian jets). When ARH missiles (specifically the AMRAAM) are launched in STT, they give a warning like a SARH missile does, and this appears to be incorrect. The SARH missiles give a launch warning because the fighter radar switches to continuous wave (CW) illumination at launch (which actually isn't correct for some SARH but thats another topic), as described in the DCS F-15C manual on page 85:

 

 

"Semi-Active Radar Homing (SARH). Such seekers home in on the reflected radar energy from the launch aircraft’s continuous wave radar. (R-27R/ER, AIM-7, R-33)"

 

 

Indeed, later in the F-15C manual (page 87) it states of the AMRAAM that:

 

 

"The missile’s autopilot combines several sub routines to aid the missile in reaching its target with out continuous wave illumination from the launch aircraft: corrected-inertial navigation at the first and second flight trajectory legs and active radar at the terminal leg."

 

 

This is confirmed by other sources such as "Distributed Simulation Testing for Weapons System Performance of the F/A-18 and AIM-120 AMRAAM". On pages 3-4 it is stated that:

 

 

"The AMRAAM operates in several modes. The preferred launch mode is the Command Inertial mode in which the missile receives targeting instructions from the aircraft through the use of an RF data link which is updated every 0.5 to 1 second depending on the launch mode of the aircraft radar."

 

 

There is no mention of the radar switching to CW, so why is the RWR giving a CW warning on the launch of ARH? We also know that CW isn't needed because TWS mode obviously does not go CW, yet it is capable of guiding AMRAAMs.

[nighthawk2174]

Yeah i'm not sure about this, it does seem reasonable you shouldn't get a launch warning (unless modern R

) but i'm not expert by any means oncesoever. Maybe try PM'ing BeamScanner and see what he says? He is far more knoledgeable on this than I am. Edited April 11, 2020 by nighthawk2174

[hein22]

ARH launched in STT do give RWR warnings because they do CW. Correct behavior afaik. If you want not to give a warning use TWS.

[hein22]

Additionally, continuous wave is for locking. Launch warnings are given when command data link from side lobes are detected. The section you quoted is specifically talking about TWS.

[dundun92]

The question is more why its going CW. For example, the APG-65/73 doesn't even HAVE a CW emitter, but our hornet shows a CW launch warning for AMRAAMs in STT, so that's not the explanation. For the datalink you very well could be correct there I suppose, but would the symbology be the same as SARH CW, or would it be different?

Also, no, CW is not for locking, as I said the APG-65/73 and the Su-27 radars dont even have a CW transmitter and they can lock people just fine.

[Mars Exulte]

ARH missiles are dependent on the launching aircraft initially for guidance, effectively operating in the same fashion as a SARH until they get within a range their much smaller radar can track the target and go active (referred to as going pitbull). As result the receiving aircraft is going to interpret your radar activity in a similar fashion, with higher intensity and more frequent refreshes necessary for weapon guidance. Whether it's ACTUALLY ''CW'' or not, it is apparently being interpreted in a very similar fashion, and the presence or absence of CW emitters is not relevant. It's an abstract display to tell you somebody's shooting at you.

[hein22]

Source for stating that those radars don't have CW?

[dundun92]

Source for stating that those radars don't have CW?

For the Hornet its "F/A-18 AN/APG-65 RADAR CASE STUDY REPORT" on p. 136. For the Flanker its not any specific source afaik, but rather the fact that there is no source indicating a CW illuminator on the radar.

[hein22]

For the Hornet its "F/A-18 AN/APG-65 RADAR CASE STUDY REPORT" on p. 136. For the Flanker its not any specific source afaik, but rather the fact that there is no source indicating a CW illuminator on the radar.

 

You misunderstood the sentence there. On p136 it is explaining how pulse doppler radars work in general as opposed to old CW ones. It is not saying that it lacks that mode for lock on.

[hein22]

In fact, it mentions that what it lacks is a separate CW illuminator.

[dundun92]

In fact, it mentions that what it lacks is a separate CW illuminator.

You cant guide on CW without a CW illuminator

[hein22]

You cant guide on CW without a CW illuminator

 

1st: you don't, you guide with command data link. Remember we are talking about ARH here. CW is for LOCK, not for guidance. 2nd: CW can be achieved with the PDR

[dundun92]

 

 

Except that ARH terminal guidance is nothing like SARH. With SARH the airplanes radar is illuminating the target for the SARH seeker to find. ARH mid-course guidance is INS datalink, which as the source in the original post said updates every 0.5-1 sec. The missile's seeker isn't doing anything.

[dundun92]

1st: you don't, you guide with command data link. Remember we are talking about ARH here. CW is for LOCK, not for guidance. 2nd: CW can be achieved with the PDR

STT is NOT CW, if thats what you are thinking. CW is for SARH guidance, you can see that in various sources such as the AIM-7(D)? SMC, and NATOPS P-820.

[dundun92]

2nd: CW can be achieved with the PDR

Source? All the sources Ive seen mention a separate CW illuminator for CW guidance.

[hein22]

Source? All the sources Ive seen mention a separate CW illuminator for CW guidance.

 

Every modern radar has CW in its PD assembley. How would they fire SARH then?

[dundun92]

Every modern radar has CW in its PD assembley. How would they fire SARH then?

Because most modern SARH missiles don't need CW to begin with. If you look at the doc i posted about the APG-65, it has this on page 2 "The F-15 proved the feasibility of providing SPARROW compatibility using the high PRF pulse doppler waveform negating the need for a separate transmitter with its inherent reduction in system reliability.". Also if you look at the AIM-7F SMC, it says that it can guide on both PD and CW. And if you look at the F-15Cs -34, FLOOD mode (which is designed to guide sparrows) is a HPRF mode, not CW

Edited April 13, 2020 by dundun92

[hein22]

..Because most modern SARH don't need CW to begin with?

 

Are you asking or being funny? I don't get it sorry, not a native english speaker here. CW in pulsed doppler radars are performed via PDI. You are confusing lock, launch and guidance. Those are 3 different stages. CW or PDI is when you are being locked by a radar. It focuses the energy on a small beam to keep you on sight at "all" times. Then at launch the side lobes are used for datalink command guidance which the enemy's RWR detects and provides warning for. However there is something odd in DCS, that when locking with sparrow you get PDI indication on radar, but when locking with amraam you get the PRF. So I will stop here and let others more experienced tell us how it is done IRL.

[dundun92]

Are you asking or being funny? I don't get it sorry, not a native english speaker here. CW in pulsed doppler radars are performed via PDI. You are confusing lock, launch and guidance. Those are 3 different stages. CW or PDI is when you are being locked by a radar. It focuses the energy on a small beam to keep you on sight at "all" times. Then at launch the side lobes are used for datalink command guidance which the enemy's RWR detects and provides warning for. However there is something odd in DCS, that when locking with sparrow you get PDI indication on radar, but when locking with amraam you get the PRF. So I will stop here and let others more experienced tell us how it is done IRL.

No that was meant to be a statement sorry, but the point is STT (when you lock someone) is not CW, its still a Pulse Doppler radar mode. And neither do SARH missiles need CW to guide, HPRF Pulse Doppler is fine for the AIM-7F and up and the R-27ER.

[hein22]

No that was meant to be a statement sorry, but the point is STT (when you lock someone) is not CW, its still a Pulse Doppler radar mode. And neither do SARH missiles need CW to guide, HPRF Pulse Doppler is fine for the AIM-7F and up and the R-27ER.

 

But I think it is still PDI, so some sort of CW small beam is still used.

[dundun92]

But I think it is still PDI, so some sort of CW small beam is still used.

And im just curious, what does PDI stand for?

[hein22]

And im just curious, what does PDI stand for?

 

Pulsed Doppler Illumination

[dundun92]

Pulsed Doppler Illumination

Yes, pulsed, not CW, which is exactly the point I was making.

[hein22]

Yes, pulsed, not CW, which is exactly the point I was making.

 

To your original point: Launch warning is still provided due to side lobes.

[dundun92]

To your original point: Launch warning is still provided due to side lobes.

Rgr I get that, im just wondering if the symbology should be any different in that case.