RWR in the Black Shark

[VMFA117_Poko]

Do SAMs radars see not moving flying low objects? Doppler radar shouldn't, am I right?

[Yellonet]

Do SAMs radars see not moving flying low objects? Doppler radar shouldn't, am I right?

A doppler radar will probably react to the moving rotor blades even if the helo itself is hovering.

[VMFA117_Poko]

^ Right

[Rhen]

If you think you won't be picked up by a fighter while hovering, then you'd be wrong, actually. Helos show up as a target that is stationary on the B-scope, but with an airspeed readout, as long as the blades are turning.

 

So, sorry. You're not invisible to fighter FCR unless you're on the ground AND your blades aren't turning at any significant speed.

 

The same is true for most modern SAM systems as well.

Edited July 11, 2008 by Rhen

[GGTharos]

It also looks like SALCOS conveys a few types of missiles.

 

TOW's (Wire Guided SALCOS)

SA-8's (Radio Guided SALCOS)

and there are also laser guided SALCOs (Do hellfires/vikhrs fall under that?)

 

Neither hellfires nor Vikhrs fall under that. Hellfires use proportional navigation, and the guidance is done by semi-active radar.

The Vikhr is a beam-rider, not SACLOS (SACLOS implies you send commands to the missile ... not so with Vikhr, however the behavior is more or less the same)

 

Also it looks like your Tunguska's fire SA-19s? Arn't those radar guided?

 

http://www.army-technology.com/projects/tunguska/

The whole system seems to be radar based? (Same tunguska you were talking about?)

 

Same one. The missile is radio-SACLOS or radio-beam rider, I forget which. You can aim the radio beam with an optical sight when the radar is not available (due to jamming, for example).

[Feuerfalke]

Wrong, actually. Helos show up as a target that is stationary on the B-scope, but with an airspeed readout, as long as the blades are turning.

 

So, sorry. You're not invisible to fighter FCR unless you're on the ground AND your blades aren't turning at any significant speed.

 

 

I doubt that.

 

For search-radars with Pulse-Doppler, your speed is calculated by 2 or more consecutive reflections of radar emissions (pulses). As your rotors from most sides only make a minor fraction of your whole silhouette, if at all, the reflection is "blured" very, very, very slightly. Remember, even sophisticated radars use wavelengths about 2cm IIRC. Considering how thin rotorblades are makes this an even less likely effect.

 

For targeting radars, which mostly use a continuous-wave-radar, the frequency shift while approaching or flying away is important, but that won't change the position from where the emissions were reflected, so it wont transfer into displayed speeds. Remember, the speed is calculated from the movement of the contact over time, not because some information was inconclusive.

 

Besides that, you forgot that the rotor under health conditions does not only move in one direction. So while it goes to the front on one side, it goes back on the other. With the KA-50 it's even more complicated.

 

 

So, with the background of being a radar-operator at my time at the Navy, let me sum it up like that:

If you are stationary, you are less likely to be detected by any means, but you will less likely draw attention from a ContinuousWave-Radar, because you won't cause any major frequency-shifts. Because of that, you can also beam a CW-Doppler-Radar, btw.

&

As long as you are not behind a solid cover, any radar can detect you, no matter if you are on the ground or painted pink. It's just a matter of where the radar is and what type of objects are behind you.

 

The best thing is to have something in your back and in your front, when confronted with radar. The object in front of you can block the waves, the object behind you will be visible anyway and make it harder to detect you in front of it.

[GGTharos]

^^^^

 

If you recall the the gulf war shoot-down of a Mi-8 with a GBU ... it was detected by an F-15E from 50nm in A2A mode, while on the ground with its rotors spinning. The heli lifted off when the GBU was in-flight.

 

The other incident of note was the blackhawk shoot-down. The helicopters were detected deep in mountainous terrain while flying low (200', IIRC) at 40nm by F-15Cs. They were shot down with one AMRAAM and one sidewinder.

 

If you're a helicopter and you're operating in an area with enemy F-15's or F-16's, leave the engines off. ;)

Rhen has a pretty good idea of what he's talking about :D

Edited July 11, 2008 by GGTharos

[Yellonet]

But as you say, the rotor is moving both towards and away from the radar emitter, in quite a hurry, that should show up as movement or at least something?, and yes, the blades are quite thin but they would rarely be angled like that towards the emitter.

[Feuerfalke]

^^^^

 

If you recall the the gulf war shoot-down of a Mi-8 with a GBU ... it was detected by an F-15E from 50nm in A2A mode, while on the ground with its rotors spinning. The heli lifted off when the GBU was in-flight.

 

The other incident of note was the blackhawk shoot-down. The helicopters were detected deep in mountainous terrain while flying low (200', IIRC) at 40nm by F-15Cs. They were shot down with one AMRAAM and one sidewinder.

 

If you're a helicopter and you're operating in an area with enemy F-15's or F-16's, leave the engines off. ;)

Rhen has a pretty good idea of what he's talking about :D

 

 

Do you have a link for that? I don't know how often this happened, but the only engagement of an F-15E with GBUs against Helos I know of, was Air Force Capt. Tim Bennett in 1993 in Iraq.

 

He didn't detect the helo on the ground, but his 2 wingmen, who were already airborne and recognized the leader still standing on the ground via FLIR, looking down at the targets and the airbase below.

 

He decided to put a GBU-10 on him, either to eliminate him or the stuff below and had his wingman 4 miles behind his him, to keep his targets locked with A2A-mode. By the time the helo took off, the bomb was already on it's way and the RIO managed to keep the target painted, though it was going at 100kts already. It was a direct hit.

 

Link to the first hand report:

http://www.f-15estrikeeagle.com/articles/story_airforce/airforce.htm

 

 

@ Yellonet

 

If you look at a hovering helo from the front, do you see it moving? No? Why, the blades are moving, too? You don't think it moves around a lot, because you will notice the large body a lot more than the barely visible rotors, right? Same is for Radar in CW-mode and it's even worse with Pulse-Radar, as with this example, it represents 2 snapshots compared to another.

Edited July 11, 2008 by Feuerfalke

[arneh]

If you recall the the gulf war shoot-down of a Mi-8 with a GBU ... it was detected by an F-15E from 50nm in A2A mode, while on the ground with its rotors spinning. The heli lifted off when the GBU was in-flight.

 

Once previously when the topic came up I quoted the pilots from that flight that found the hovering helicopter with AA-radar and then dropped a LGB on it:

http://forums.eagle.ru/showpost.php?p=437835&postcount=52

Edited July 11, 2008 by arneh

[GGTharos]

Thanks Arneh. Feuerfalke, that is the same incident.

[Feuerfalke]

Roger that, thanks for the link, arneh.

[nscode]

^^^^

 

If you recall the the gulf war shoot-down of a Mi-8 with a GBU ... it was detected by an F-15E from 50nm in A2A mode, while on the ground with its rotors spinning. The heli lifted off when the GBU was in-flight.

 

The other incident of note was the blackhawk shoot-down. The helicopters were detected deep in mountainous terrain while flying low (200', IIRC) at 40nm by F-15Cs. They were shot down with one AMRAAM and one sidewinder.

 

If you're a helicopter and you're operating in an area with enemy F-15's or F-16's, leave the engines off. ;)

Rhen has a pretty good idea of what he's talking about :D

 

 

Do you remamber the Mi-8 shot down in Serbia? That's right, you don't. There weren't any. And Mi-8 pilots say RWR did help. The only reason Ka-50 doesn't have a RWR is that it is presumed that no enemy radars would be around, and that it's pure dead weight.

[GGTharos]

I don't even remember NATO airpower caring about helis at all. They seemed to be more concerned with fighters, strikers, and SAM radars. And probably power lines, later on.

[D-Scythe]

I doubt that.

 

For search-radars with Pulse-Doppler, your speed is calculated by 2 or more consecutive reflections of radar emissions (pulses). As your rotors from most sides only make a minor fraction of your whole silhouette, if at all, the reflection is "blured" very, very, very slightly. Remember, even sophisticated radars use wavelengths about 2cm IIRC. Considering how thin rotorblades are makes this an even less likely effect.

 

Um, the rotors make up virtually the ENTIRE silhouette of a helicopter. The rotor disc area for the Ka-50 is over 300 m^2.

 

For targeting radars, which mostly use a continuous-wave-radar, the frequency shift while approaching or flying away is important, but that won't change the position from where the emissions were reflected, so it wont transfer into displayed speeds. Remember, the speed is calculated from the movement of the contact over time, not because some information was inconclusive.

 

It doesn't matter if the helicopter is static - it's rotor blades aren't. That's what gets picked up and tracked.

 

For example, on your radar scope, a hovering helicopter contact will appear stationary - that is, the radar "brick" won't move. But when you lock it up, your radar will calculate the speed of the rotors, NOT the entire helicopter. I think that's what Rhen was saying.

 

Besides that, you forgot that the rotor under health conditions does not only move in one direction. So while it goes to the front on one side, it goes back on the other. With the KA-50 it's even more complicated.

 

Forgot what? The rotor blades MOVE - or more specifically, generate radial movement - that's all that matters for a doppler radar.

Edited July 11, 2008 by D-Scythe

[nscode]

They carried about them when they could find them - on the ground. The reason choppers flew at all was to be constantly relocated. NATO even happily bragged about bombing a heli that turned out to bi a Mi-2... either civilian or Albanian.

[GGTharos]

My point is, targets of opportunity as opposed to actively sought after targets. :) There's no denying that the terrain helped as well, not to mention the potential confusion with civvy choppers and the careful movements by the Serb army.

 

The point still remains: Don't get caught in a heli with its rotors spinning while a fighter's searching that area. I think there's enough proof out there to indicate it's a bad idea.

In general the Serb army quite simply did a better job of hiding themselves and their movements than the Iraqi army did - and to some extent, the terrain really helped here.

[nscode]

I concur with that, but add: but if there is any chance there will be any radars against you - bring a RWR :)

[GGTharos]

Yeah, at least you'll know to go hover behind the nearest hill/building :)

[ThunderChief]

Similar to helicopter rotor blades are the fan-blades of jet engines, which can also be detected by radar and allow to identify the type of engine/airplane. Hiding those fan-blades is a mayor problem of stealth aircraft.

As helicopter rotor blades are much larger you can asume that they are fairly easy to detect by radar in theory. But on the other hand it depends wether the radar software is capable of doing so.

[EvilBivol-1]

The argument that the rotors are "invisible" rests on the fact that they are constructed of plastic composites, unlike engine compressor blades. The "purity" of this argument is questionable.

[GGTharos]

Similar to helicopter rotor blades are the fan-blades of jet engines, which can also be detected by radar and allow to identify the type of engine/airplane. Hiding those fan-blades is a mayor problem of stealth aircraft.

 

The idea with the fan is that they are 'facing' the incoming radar straight on. As for aircraft identification, it's moved way past the fans a long time ago ;)

 

For stealth aircraft you have three RCS concerns, mainly: Fans (you already mentioned), Radar dish (have you noticed the Raptor's radar is not mounted vertically, but tilted?), and the cockpit. Golden tinted canopies are used to reduce RCS.

[Feuerfalke]

Similar to helicopter rotor blades are the fan-blades of jet engines, which can also be detected by radar and allow to identify the type of engine/airplane. Hiding those fan-blades is a mayor problem of stealth aircraft.

As helicopter rotor blades are much larger you can asume that they are fairly easy to detect by radar in theory. But on the other hand it depends wether the radar software is capable of doing so.

 

:huh:

 

A-7

 

 

(Draken)

[Feuerfalke]

The argument that the rotors are "invisible" rests on the fact that they are constructed of plastic composites, unlike engine compressor blades. The "purity" of this argument is questionable.

 

As most rotorblades have a metal leading edge, that isn't the main argument here as I see it.

[Rhen]

Grüß Gott,danke für Ihren Militärdienst. Entschuldigen Sie mich bitte, aber mein Deutsch ist schrecklich! :doh:

I doubt that.

Then you're knowledge of airborne fire control radars is inadequate to this discussion. :smartass:

...For targeting radars, which mostly use a continuous-wave-radar, the frequency shift while approaching or flying away is important, but that won't change the position from where the emissions were reflected, so it wont transfer into displayed speeds. Remember, the speed is calculated from the movement of the contact over time, not because some information was inconclusive.

Modern fighter targeting radars as well as SAM radars are pulse dopper variety & not continuous wave, which are more easily vulnerable to ECM. All that's required to target a semi-active radar homing missile is HPRF. Active radar missiles also use HPRF for terminal guidance to their target, once it's acquired.

Besides that, you forgot that the rotor under health conditions does not only move in one direction. So while it goes to the front on one side, it goes back on the other. With the KA-50 it's even more complicated.

I didn't forget this, as it's blatantly obvious. You must not know that this is irrelevant to FCRs of modern aircraft and SAM systems. The fact that the blades are in motion cause enough of a radar return that we usually get a velocity readout on the blades, which settles down as the target is sorted. We know the target is a helo when the velocity doesn't match it's groundspeed - initially.

So, with the background of being a radar-operator at my time at the Navy, let me sum it up like that:

If you are stationary, you are less likely to be detected by any means, but you will less likely draw attention from a ContinuousWave-Radar, because you won't cause any major frequency-shifts. Because of that, you can also beam a CW-Doppler-Radar, btw.

So, with your background, if it's recent, I would've thought you'd be more familiar with modern airborne and SAM radars. Perhaps you were in the navy during WW2? :doh: Sitting stationary on the ground is, in general, a good way not to be detected by a modern pulse doppler equipped fighter. However, it's not so good while you're trying to beat the air into submission with your rotor blades, regardless of whether you're stationary - on the ground or hovering. Once we notice you, the only way we will lose you is if you terrain mask, or land and spin down the rotors.

He didn't detect the helo on the ground, but his 2 wingmen, who were already airborne and recognized the leader still standing on the ground via FLIR, looking down at the targets and the airbase below.

I don't think you're comprehending what you read. Either way, it was Bakke, Bennett's WSO who picked up the Hinds at 50NM as they were moving. The Hinds were moving, stopping to drop troops off, then moving again, all the while lock was maintained. As they got within weapons employment distance, they switched command of the radar from the WSO to the pilot - as mudhen crews are trained - and Bennett maintained lock as Bakke lazed the target. Bennett later says the following in the article YOU quote: "The radar would stay locked on them when they were on the ground because the moving rotor blades were picked up."

If you look at a hovering helo from the front, do you see it moving? No? Why, the blades are moving, too? You don't think it moves around a lot, because you will notice the large body a lot more than the barely visible rotors, right? Same is for Radar in CW-mode and it's even worse with Pulse-Radar, as with this example, it represents 2 snapshots compared to another.

Completely incorrect for a modern pulse-doppler equipped fighter. As I've said before, on my B-scope, I have a solid return - none of this "blurred" contact stuff you report. However, I also have a velocity readout on that stationary target that is initially high, then settles down. This is a clear indicator - at least to me & my training, that I've locked up a helicopter. You don't seem to realize that we've modernized our equipment since you apparently were in the navy.