F-15 radar ... what range to see a KC-10?

[Kula66]

F-15 searching for a tanker, approx 30degs off my nose ... what range do you get to see it on radar?? I get about 45miles!!! This seems way low. Given that a KC-10 is a BIG target ... anyone any idea what it should be? 100? Max search range (160)?

 

Thanks,

James

[SAM-Smasher]

I think this is difficult to say, it also depends on your altitude and the direction the KC-10 is heading in relation to your flight path, have you tried varying the conditions for this?

 

It is a big target, but even a big target can have weaker returns based on the conditions. :wink:

[Kula66]

Same altitude @6550, KC doing 267, F-15 450mph, KC-10 going 150, F-15 going 180 ... and up he popped at 45miles ... perhaps I'll try some more testing!

 

James

[Kula66]

Ok, just ran a head to head and picked it up at 120ish miles which seems more like it ... still the other value does seem a bit low for such a big target - I know very little about radar, so it may be right, anyone know for sure?

 

James

[SAM-Smasher]

KC-10 going 150, F-15 going 180

 

If I read you correct, if this is the heading of both of the aircraft at time of detection, the KC-10 is essentially heading away from you, this will weaken its radar return, because the velocity of closure has been reduced.

 

If you try some testing I would be very keen to see what your results are :wink:

 

edit: Just read your post, and 120 miles sounds about right, what were the conditions? or when you say head-on, do you mean both aircraft heading towards each other? in which case that makes perfect sense to me!! :D

[Octav]

KC-10 going 150, F-15 going 180

 

If I read you correct, if this is the heading of both of the aircraft at time of detection, the KC-10 is essentially heading away from you, this will weaken its radar return, because the velocity of closure has been reduced.

 

If your try some testing I would be very keen to see what your results are :wink:

 

For a tail-on intercept, it is actually pretty good - a head-on shot, with the fighter going at 800 kts, and the target at 400 kts, should give you some 100 miles

[britgliderpilot]

KC-10 going 150, F-15 going 180

 

If I read you correct, if this is the heading of both of the aircraft at time of detection, the KC-10 is essentially heading away from you, this will weaken its radar return, because the velocity of closure has been reduced.

 

If you try some testing I would be very keen to see what your results are :wink:

 

edit: Just read your post, and 120 miles sounds about right, what were the conditions? or when you say head-on, do you mean both aircraft heading towards each other? in which case that makes perfect sense to me!! :D

 

The velocity of closure is determined by measuring the doppler shift of the radar reflection - a doppler shift should not have any effect, though, on the strength of the reflection.

 

The RCS should vary with the angle you're seeing the KC-10 from, though . . . . don't know if ED modelled that.

[SAM-Smasher]

For a tail-on intercept, it is actually pretty good - a head-on shot, with the fighter going at 800 kts, and the target at 400 kts, should give you some 100 miles

 

Thanks for the correction, any idea why he may have only picked up the KC-10 at 45 miles out in that case? :?

 

edit:

The velocity of closure is determined by measuring the doppler shift of the radar reflection - a doppler shift should not have any effect, though, on the strength of the reflection.

I should have kept my mouth shut :oops:

[Cromewell]

For a tail-on intercept, it is actually pretty good - a head-on shot, with the fighter going at 800 kts, and the target at 400 kts, should give you some 100 miles

 

Thanks for the correction, any idea why he may have only picked up the KC-10 at 45 miles out in that case? :?

 

100 miles for head on, 45 is quite good detection range for tailing

[Kula66]

>>100 miles for head on, 45 is quite good detection range for tailing<< What do you base this on? Do you fly F-15s? Do you have an refences? It just seems odd that one of the most powerful A2A radar mounted in a fighter can only detect a massive target at 45miles ... over the sea (no ground clutter), no jamming, same height ...

 

James

[Raploc]

>>100 miles for head on, 45 is quite good detection range for tailing<< What do you base this on? Do you fly F-15s? Do you have an refences? It just seems odd that one of the most powerful A2A radar mounted in a fighter can only detect a massive target at 45miles ... over the sea (no ground clutter), no jamming, same height ...

 

James

 

Please read this:

 

http://www.theweatherprediction.com/habyhints/231/

 

It might give you a slightly better understanding why Doppler radars (and yes also the F-15's radar) have some trouble picking up low Doppler returns.

The N-019 radar supposedly can track a fighter sized target from the rear at a max range of 19nm, so 45nm for the APG-63 is not so bad. :D

[Kula66]

But this is for a KC-10 ...

 

James

[golfsierra2]

Same altitude @6550, KC doing 267, F-15 450mph, KC-10 going 150, F-15 going 180 ... and up he popped at 45miles ... perhaps I'll try some more testing!

 

James

 

It is not a matter of relative speed, but of the relative angle that you try to get a radar contact from the KC. You see, if hit from the side (abeam) it will bring you a much stronger echo than if you illuminate the tanker right from astern on head on. If the simulation works correct and these physical rules were considered by the programmers, you probably will see a KC 130 from 80-90 km when you look at it from the side.

[Raploc]

Same altitude @6550, KC doing 267, F-15 450mph, KC-10 going 150, F-15 going 180 ... and up he popped at 45miles ... perhaps I'll try some more testing!

 

James

 

It is not a matter of relative speed, but of the relative angle that you try to get a radar contact from the KC. You see, if hit from the side (abeam) it will bring you a much stronger echo than if you illuminate the tanker right from astern on head on. If the simulation works correct and these physical rules were considered by the programmers, you probably will see a KC 130 from 80-90 km when you look at it from the side.

 

I'm sorry but this is wrong. Doppler-pulse radars depend largely on relative speed, and the radar cross section of a plane depends on more factors than just the size of a surface returning the radar signal.

 

 

Greetz,

 

Raploc

[Kula66]

Ok, so I am sure nobody is going the claim the KC-10 is stealthy ... I would have thought it has one of the largest RCS in the air!! I would suggest that the RCS is less from the front, than from a 3/4 angle. So the detection range should be higher. Mind you with all those compressor faces visible, I guess that could be argued.

 

The head on lock was obviously with very high closure ... say 300 + 350mph so big doppler shift to see, the other scenario was (please correct this logic if it is wrong!) 300 - (350 x cos 30ish) = 3mph ... inside the doppler gate ... so I shouldn't have been able to see it at all? Or am I completely wrong in the way I am looking at this?

 

Thanks for the reference Raploc ... the info for the Mig is interesting, but that is against a fighter AND for a radar that is known to be quite a bit wweaker than the F-15s.

 

Perhaps I need to test from a number of angles and plot it out ...

 

Thanks, James

[Raploc]

Kula66 let me know the results of the testing. I find this thread very interesting. I just know a itty bitty thing about radar, so any new information is welcome :D

 

Greetz

 

Raploc

[Kula66]

Well, here is a few quick results:

 

KC-10 - 300mph

F-15 -350mph

Head-on 128miles

Tail-on 42miles

Side-on 82miles -despite being in the doppler notch!

1/4 on front 120miles

3/4 on rear 53m - 56deg off tanker course

3/4 on rear 45 - 30degoff tanker course

 

And the moral is, don't go looking for targets from behind!!

 

Anyone with real knowledge like to comment :?

 

James

[Octav]

Well, here is a few quick results:

 

KC-10 - 300mph

F-15 -350mph

Head-on 128miles

Tail-on 42miles

Side-on 82miles -despite being in the doppler notch!

1/4 on front 120miles

3/4 on rear 53m - 56deg off tanker course

3/4 on rear 45 - 30degoff tanker course

 

And the moral is, don't go looking for targets from behind!!

 

Anyone with real knowledge like to comment :?

 

James

 

What are the altitudes of the figther and the target?

If you were above 10k feet, and the tanker even higher, the numbers are good - electronics don't produce miracles - for a given RCS, abd a given antenna diameter and power output, you're going to have similar results, regardless of the electronics (they might give you a few percent extra, but don't expect wonders only because it's the F-15 radar).

 

Octav

[Kula66]

Both at 6500' ... mainly over the sea ... although the tail chase went over land give the slow overtake.

 

James

 

PS> For info, it didn't pick up a Mig-29 until 22miles in a tail chase but 63 head on.

[Octav]

Both at 6500' ... mainly over the sea ... although the tail chase went over land give the slow overtake.

 

James

 

PS> For info, it didn't pick up a Mig-29 until 22miles in a tail chase but 63 head on.

 

Hm... for that alt... that's more than enough...

For reference, the 29's RCS is about 4 sqm. Don't know the KC-10's RCS.

[Cromewell]

>>100 miles for head on, 45 is quite good detection range for tailing<< What do you base this on? Do you fly F-15s? Do you have an refences? It just seems odd that one of the most powerful A2A radar mounted in a fighter can only detect a massive target at 45miles ... over the sea (no ground clutter), no jamming, same height ...

 

James

 

sorry, I wasn't clear on where I was basing my information for this, I was refering to my experience in game with radar detection range for head on and tailing situations at equal altitude. Weather the ranges are true in real life I don't know but I would think they must be close.

[crazyleggs]

The RCS from a front aspect target will always be higher than any other aspect due to the fan/turbine blades. That's why an aircraft such as the B-1 has ducting vanes in front of the ehgines. It greatly reduces RCS.

 

As far as doppler goes, most doppler radars have different modes depending on the ranges it looks for targets. As a general rule, for long ranges the PRF increases to get a better doppler definition. This is where the notch comes in handy, no matter what airframe you are flying in or against. Depending on the radar, a notch as low as 60 deg aspect may be good enough to break lock and or disappear (when not locked). The best bet for a defender is to notch and change in elevation to make life miserable for the attacker. The attacker on the other hand, has to reposition for better aspect based on his best guess to re-acquire.

 

For shorter range engagements, generaly a pulse doppler radar will change to a lower PRF to gain better range definition. This is where a notch has to be executed perfectly to be effective. It's effectiveness is based on timing, angle of arrival accuracy (RWR) and what gate the attacker's radar is set on.

 

On another note, if you fly online with a Mig-29 and R77s you can be quite effective visually. Fly low, keep scanning the sky around you, and keep that radar off. Most of the time, they'll never see you coming. Most of the time...

 

Thanks.

[britgliderpilot]

Re the short detection ranges in chase for the N019 . . . . .

 

 

I'll be very interested to find out how well this is modelled with the new Russian radar modes in v1.1 - three different PRF settings and all that :D