From: opus@cbnewsc.cb.att.com (robin.g.kim)
Subject: Re: Radar and IR signatures of choppers
Organization: AT&T
Distribution: na
Date: Tue, 15 Sep 1992 14:06:26 GMT

In article <BuLo73.4st@watserv1.uwaterloo.ca> ptran@watserv1.uwaterloo.ca (Phat H Tran) writes:
>I received this letter from mccullou@cae.wisc.edu concerning the radar
>and IR signatures of helicopters.  I am posting it here with permission:
>
>
>From: mccullou@cae.wisc.edu
>
>Okay, about IR signiture of Helicopters and their radar signiture.  A helo
>does have a very significant helo signiture, IF you have a surface search
>radar.  The F-16 has only air search radar, so it is not designed to counter
>ground return.

This is not true.  All airborne pulse-doppler radars implicitly counter
ground return by filtering out targets that are closing at the same
speed the aircraft is moving.  If the target's own velocity toward or away
from the antenna is fast enough (but not too fast, though this limitation is
unlikely to be encountered in real life), pulse-doppler radar will pick it out
from the ground return with no problem.  If the target is beaming the radar,
it may not be picked up at all.

An additional complication is side-lobe clutter, which limits the
effectiveness of pulse-doppler radar operating from low altitudes (and
may be other types of radar as well, but I can't remember).  This usually
does not come into play in look-down shoot-down situations.

>As to the blades messing up the reflection, PLEASE!!!!
>The rotors are basically still compared to the burst of radar.  You would get
>a solid return off the blades as well as off the body, the tail, the engine...

Oh, REALLY?!?  How fast do rotors move?  How fast does your car move when
the state trooper aims his radar gun at you?  Apparently, the doppler effect
does not require the target velocity to be near the speed of light.  :^)
Also, Robert Shaw's "Fighter Combat: Tactics and Maneuvering" mentions the
difficulty of locking onto helicopters with radar.  I don't think the guy
is infallible, but I'd surely believe his book before I believe something
I read on the net!

>No existing helicopter today is stealth!!!!  (The LHX has not even a
>prototype and I haven't heard of the European stealth helicopter being
>produced yet.)
>
>Now to the IR signiture of helicopters.  The AIM-9L model is a very 
>sophisticated model.  This means that it can lock on to the heat generated
>by the leading edges of the rotors.  (it was designed for ALL-ASPECT,  this
>means the leading edges of even a very slow flying aircraft.)  The engines,
>Even though modern gunships have a IR-masking feature, are quite hot enough
>for even somewhat older IR missiles.  Remember Afganistan?  Stinger missiles
>blotted Mi-24 Hinds out of the sky (As well as anything else in range).  
>A stinger is a smaller seeker and warhead than the AIM-9L.
>
>I don't know about the game, but if it doesn't allow a AIM-9L or better
>IR missile to lock on quite easily, it has a problem.  I CAN understand the
>problem with RADAR missiles, especially if the helicopter is flying low.
>Sorry, guys, not everything in Falcon 3 is perfect I guess..

Oh well.  I'll take the best, even if it isn't perfect (though improvements
are always welcome).

Rob
ihlpy!opus@att.att.com
Newsgroups: comp.sys.ibm.pc.games