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Old 08-24-2019, 11:11 PM   #71
Weta43
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I'd imagine making the blades stealthy is slightly more complicated than making them out of composites, but I find the idea of the hub being tracked in TWS/STT surprising,

There must be a doppler gate on the TWS/STT track otherwise it's going to track every bush and goat on the ground while looking down - any idea what it is ?

While the rotors are spinning pretty fast, and the hub looks like it's spinning fast, if you take a UH-60, the hub's actually only spinning at 258 rpm.

Eyeballing it, it looks to be about 1m in diameter - maybe up to 1.5m.

That means that while all the components are angular and 'shiny', and so might provide quite a good reflection, the maximum groundspeed of any component at the very periphery of the hub is only between 30 mph and 50 mph & everything inboard of that is moving slower - to zero at the actual hub (while in a hover obviously).

Surely the gate's higher than 30 mph in lookdown, or you'd have every jackass in his SUV showing up in TWS ???

So blades and tail-rotor - sure, I can see that.
Hub - I'm less convinced at the moment..
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Old 08-25-2019, 03:03 AM   #72
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Quote:
Originally Posted by Murey2 View Post
Hello.


I just want to say in simple short way that the new Ka-50 must have a RWR which is a real part of other Russian helicopters Mi-24 and the Ka-52 and so on. the Fact that the early Ka-50 didn't have RWR because it was a prototype tested in a RADAR absence threat environment!


Nowadays in real life a Ka-50 if it was continued it would have had RWR due to the new nature of it's modern operation domain.


ED even the oldest RWR like found in the MiG-21 and early Mi-24s will do. I want to see it in the new Ka-50. In fact for me a RWR is more important than a IRCCD.


To all the people who care about this please make sure that you show that. Thanks.
First the IGLAS... now the whiners want another fantasy feature..... to better compete in airquake servers.

Why not just go full force and add railguns and full on stealth RCS reduction while your at it.
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Old 08-27-2019, 09:22 AM   #73
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I got curious and did some math for rotor speeds vs. doppler gates: It has some math but i made it really easy to follow, can't do that with forum txt app so I made a pdf:

To sum up: Huey rotor tips at cruise are moving at 480 knots and at about 2m out they are doing 133 knots and at 1.5m out they are doing 100 knots. With these results I would assume the rotation of the inner rotor connection and the hub to be invisible to an F-14 doppler radar (which i used for the experiment). But remember that these velocities are vectorially summed to the velocity of the helicopter as a whole, so the advancing blades will go higher and the retreating blades will seem slower (so viewed from the interceptor advancing blades should be easier to see, retreating harder, from the frame of reference of the searching radar of course)

here is the pdf, its actually easy to read and you can use the equations to run this experiment on any rotors and any doppler gates you wish: It's also fun to see if the blades can come close to transonic!
Attached Files
File Type: pdf Rotor angular speed experiment for doppler gate 3.pdf (97.5 KB, 31 views)

Last edited by cauldron; 08-27-2019 at 09:37 AM.
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Old 08-27-2019, 09:44 AM   #74
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For some quick mental math for pilots!

V=w*r

if you take a tenth of you rpm's you get radians per second, multiply that by your rotor radius in meters and you get angular velocity in meters/second. take that and multiply by 2 and you get approximately your blade tip speed in knots around the hub, then for an advancing blade add you air speed ! and subtract for the receding blades!

Good approximate figure.
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Old 08-27-2019, 11:01 AM   #75
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0.2 * r * RPM ( = 0.1 * D * RPM)
That's nice - I like it.
Let me guess - starting from angular velocity - you're an engineer ?

I wondered how approximate the approximation was, so did it the math-phobe, social science major's way :-/

Pi * D * RPM * 60 * .001 to get the speed at that diameter in km/h, which simplifies to

D * RPM * 0.1885 = speed in km/h
or
D * RPM * 0.1018 for knots

which makes your angular approximation pretty close ! (.1 is pretty close to .1018 )
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Old 08-27-2019, 11:13 AM   #76
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Good work; I'll drop the rotor hub since I've got nothing to back it up - I heard things from a radar operator, but he's no longer available to ask about this.

Instead, there is a study that estimates composite rotor mean RCS at just over 2m^2 for the EC Tiger. That's approximately 1/4 to 1/5 of the RCS of a small fighter that would be detected at anywhere between 60-90nm by an APG-63. This cuts detection range by about 30%, and of course you can apply look-down to further reduce it etc. But the fact remains that it'll be picked up at comfortable BVR ranges, and that composites alone won't cut it for evading detection.

Even the raptor, being VLO, has a limit - an APG-63 could pick'em up at around 6nm (IIRC - don't quote me too much on it). It would be very hard for a heli to do better, and it shouldn't be a very hard target for a modern weapon.
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Old 08-27-2019, 07:45 PM   #77
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Quote:
Originally Posted by Kev2go View Post
First the IGLAS... now the whiners want another fantasy feature..... to better compete in airquake servers.

Why not just go full force and add railguns and full on stealth RCS reduction while your at it.
This is actually what they will give us.

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Old 08-28-2019, 12:49 AM   #78
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I didn't realize this had digressed into a tabloid, but since we're there, sure i'll take airwolf, but only if it comes with the music tracks.
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Old 08-28-2019, 12:50 AM   #79
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Originally Posted by GGTharos View Post
Good work; I'll drop the rotor hub since I've got nothing to back it up - I heard things from a radar operator, but he's no longer available to ask about this.

Instead, there is a study that estimates composite rotor mean RCS at just over 2m^2 for the EC Tiger. That's approximately 1/4 to 1/5 of the RCS of a small fighter that would be detected at anywhere between 60-90nm by an APG-63. This cuts detection range by about 30%, and of course you can apply look-down to further reduce it etc. But the fact remains that it'll be picked up at comfortable BVR ranges, and that composites alone won't cut it for evading detection.

Even the raptor, being VLO, has a limit - an APG-63 could pick'em up at around 6nm (IIRC - don't quote me too much on it). It would be very hard for a heli to do better, and it shouldn't be a very hard target for a modern weapon.

good points, heli's are not so simple are they.
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Old 08-28-2019, 12:55 AM   #80
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Quote:
Originally Posted by Kev2go View Post
First the IGLAS... now the whiners want another fantasy feature..... to better compete in airquake servers.

Why not just go full force and add railguns and full on stealth RCS reduction while your at it.

I think you're in the wrong forums. "The Expanse" season 4 fandom forums aren't here, and discussing MCRN ships is off topic
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