F-22 PMFD radar symbology

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BDF

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Unread post08 Mar 2020, 17:45

Could anyone explain why the radar scan volume is depicted this way on the PMFD? I've seen this shown on the F-22 cockpit demonstrator years ago, there's a few videos of that being demonstrated out there. It seems strange to me that its shaped this way. Below is another image of the actual display from what I'm guessing is the manufacturer's website. I note that the symbology is more F-35 like than what the F-22 was originally shown when it became public.

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falcon.16

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Unread post08 Mar 2020, 18:45

I think that for diferente range the volume track is different. How much long range is. Volumen track will decrease if you want get the same sensitivity. So they are diferent volume angles.
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Unread post08 Mar 2020, 21:45

I might be saying the same thing as falcon_16, just worded differently, but I always thought it had to do with AESA T/R modules splitting the workload unevenly. The majority of the modules being dedicated to a narrower scan cone and then relatively few modules scanning the periphery.
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Unread post09 Mar 2020, 04:41

Yes that could be why its depicted that way. However I can't imagine that's anything close to what the real performance is. For instance if you watch the NG APG-81 video on YT, you can see it quickly detect and track multiple targets beyond the circa ± 22°long range scan volume (yes I measured it.), some out to 40° out to near max range of the display (80nm.) Compared to the F-35's tactical situation display, it displays what I believe is the radar scan volume with green colored elongated shapes, interestingly with a small area in the middle with no coverage:

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Now from what appears to be an early slide about LM JAST presentation, shows the long range volume as ± 40°. In this case the long range volume is slewed left with the (much) reduced range volume visible on the right side of the TSD and A-A formats.

Image

Perhaps what is represented on the F-22 are simply notional non-representative displays and what we see now in this JAST and F-35 is more representative.
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hornetfinn

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Unread post09 Mar 2020, 09:47

BDF wrote:Yes that could be why its depicted that way. However I can't imagine that's anything close to what the real performance is. For instance if you watch the NG APG-81 video on YT, you can see it quickly detect and track multiple targets beyond the circa ± 22°long range scan volume (yes I measured it.), some out to 40° out to near max range of the display (80nm.) Compared to the F-35's tactical situation display, it displays what I believe is the radar scan volume with green colored elongated shapes, interestingly with a small area in the middle with no coverage:


I think that the small area in the middle with no coverage is a jammer effect. Basically a radar (AESA especially can do this well) discards all signals coming from the direction (certain angle) of jammer and can minimize the effects of the jammer. It seems that the no-coverage area widens with distance which would be consistent with how this method works.

F-22 symbology could be many things. It could well be what falcon.16 said about search volume. Another possibility could be passive detection range of enemy radars for the long distance. It may be that this is just a way of showing the difference between passive and active search distances and not necessarily the true scan angles for each.
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Unread post04 Apr 2020, 03:25

Don't you get no SAR map directly in front of you? But if it's close enough I suppose with the elevation difference you can still map what's under your feet so there's less blind spot the closer it gets?
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Unread post15 May 2020, 22:23

The F-22 representations look exactly like I would expect an AESA radar to look. With all radars the angle, the distance, the range of elevation(vertical angle) increase the time taken to scan an area and thus the rate at which updates come through. It would make a lot of sense, then, that a primary long range beam is used with as small an area as needed to pick up targets along with a secondary short range beam rapidly firing off after/in between to detect any close range dangerous threats slipping past. That would explain the numbers given, the radar certainly can meet those angles but the slower updates would make that not ideal. It would explain why the angles of the long range beam keep changing, pilot preference and tactical needs. And it would explain why the short range beam doesn't change angle, maximum beam width.

As for the F-35, there are a few other reasons one could imagine but here I'm just throwing out an idea rather than any expectations of it being right. The beam looks to be directly forwards and the other symbology is in air to ground mode. It would be possible that it represents DBS (doppler beam sharpening) radar modes. The technique doesn't work for objects directly towards the direction of travel as there is no relative doppler shift, The shape of the curve could explain the maximum capabilities of the radar, as both the transmitted and received energy drops as angle increases, and at quite a significant rate near the ends of its capabilities. If so then the F-35 radar is very impressive indeed being able to run DBS so effectively at such small angles. Still, I'd lean towards myself being wrong for now but its certainly an interesting idea worthy of more consideration in my opinion.
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Unread post19 May 2020, 12:42

An example on a F-16 radar.

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Unread post19 May 2020, 12:43

frostitute wrote:The F-22 representations look exactly like I would expect an AESA radar to look. With all radars the angle, the distance, the range of elevation(vertical angle) increase the time taken to scan an area and thus the rate at which updates come through. It would make a lot of sense, then, that a primary long range beam is used with as small an area as needed to pick up targets along with a secondary short range beam rapidly firing off after/in between to detect any close range dangerous threats slipping past. That would explain the numbers given, the radar certainly can meet those angles but the slower updates would make that not ideal. It would explain why the angles of the long range beam keep changing, pilot preference and tactical needs. And it would explain why the short range beam doesn't change angle, maximum beam width.

As for the F-35, there are a few other reasons one could imagine but here I'm just throwing out an idea rather than any expectations of it being right. The beam looks to be directly forwards and the other symbology is in air to ground mode. It would be possible that it represents DBS (doppler beam sharpening) radar modes. The technique doesn't work for objects directly towards the direction of travel as there is no relative doppler shift, The shape of the curve could explain the maximum capabilities of the radar, as both the transmitted and received energy drops as angle increases, and at quite a significant rate near the ends of its capabilities. If so then the F-35 radar is very impressive indeed being able to run DBS so effectively at such small angles. Still, I'd lean towards myself being wrong for now but its certainly an interesting idea worthy of more consideration in my opinion.


Yes, i think too, it could be SAR mode.
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Unread post26 May 2020, 03:23

frostitute wrote:As for the F-35, there are a few other reasons one could imagine but here I'm just throwing out an idea rather than any expectations of it being right. The beam looks to be directly forwards and the other symbology is in air to ground mode. It would be possible that it represents DBS (doppler beam sharpening) radar modes. The technique doesn't work for objects directly towards the direction of travel as there is no relative doppler shift, The shape of the curve could explain the maximum capabilities of the radar, as both the transmitted and received energy drops as angle increases, and at quite a significant rate near the ends of its capabilities. If so then the F-35 radar is very impressive indeed being able to run DBS so effectively at such small angles. Still, I'd lean towards myself being wrong for now but its certainly an interesting idea worthy of more consideration in my opinion.


So I was perusing some YT vids on F-35 cockpit demos and I noticed this one: https://youtu.be/vGU3noa1PEU?t=725

Notice during the rollout the two lobes spread apart then shrink and disappear as he comes to a full stop. I've seen on another video where the lobes shrink towards the "own ship" icon then stretch back out as the person flying the sim completed a loop. So I'm not sure what to make of it. It seems logical that it is some sensor footprint but its not clear if it is or what it is. I don't think it's an A-A footprint as I'd imagine it'd look similar to the F-22's I posted above.
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Unread post26 May 2020, 06:53

Very interesting detail you brought up BDF. I think the most likely reason is that the radar lobes represent SAR mode coverage. It seems like the lobes are tightly together when the speed is up but begin to shrink when the aircraft begins to slow down during landing. When the speed approaches zero, the lobes shrink very quickly.

Since SAR uses forward speed of the platform to artificially create a large antenna, it's quite logical that the lobes begin to shrink when speed goes below certain level. The shrinking also should start and be most apparent from the middle as the relative speed between platform (F-35) and targets is also the smallest there.

It also seems that the representations doesn't take into account the flight altitude but that might be a feature of this simulator version meant for public usage.
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Unread post27 May 2020, 19:35

hornetfinn wrote:Very interesting detail you brought up BDF. I think the most likely reason is that the radar lobes represent SAR mode coverage. It seems like the lobes are tightly together when the speed is up but begin to shrink when the aircraft begins to slow down during landing. When the speed approaches zero, the lobes shrink very quickly.

Since SAR uses forward speed of the platform to artificially create a large antenna, it's quite logical that the lobes begin to shrink when speed goes below certain level. The shrinking also should start and be most apparent from the middle as the relative speed between platform (F-35) and targets is also the smallest there.

It also seems that the representations doesn't take into account the flight altitude but that might be a feature of this simulator version meant for public usage.


Oh duh, brain flatulence on my part. You're almost certainly right. What is interesting is that you don't see the A-A radar FOV on any TSD images or this simulator. I assume its very similar to the F-22s (which is I'm sure is notional itself) but its interesting that you don't see it anywhere.
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Unread post28 May 2020, 09:35

BDF wrote:Oh duh, brain flatulence on my part. You're almost certainly right. What is interesting is that you don't see the A-A radar FOV on any TSD images or this simulator. I assume its very similar to the F-22s (which is I'm sure is notional itself) but its interesting that you don't see it anywhere.


There have been some notional A-A radar format images published. Here is one:

Image

From this presentation: https://slideplayer.com/slide/10657249/

It seems very similar format to the F-22 one. I'd really like to know how it looks like in video, but I think I'll have to wait a bit for that... :D
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Unread post28 May 2020, 09:45

Btw, it's interesting that the scan angle limits seem to be a bit higher in APG-81 than in APG-77, at least from those pictures. That indicates that APG-81 has more tightly packed with T/R modules. Not really surprising though given when those radars were developed.
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Unread post28 May 2020, 15:13

hornetfinn wrote:Btw, it's interesting that the scan angle limits seem to be a bit higher in APG-81 than in APG-77, at least from those pictures. That indicates that APG-81 has more tightly packed with T/R modules. Not really surprising though given when those radars were developed.


Its hard to tell. Those F-22 images I posted are somewhat zoomed in, but to me they look about the same when you account for the zoom differences. You could be right though. What is pretty obvious is that these are at least sanitized representations. We've seen in the NG APG-81 demo on YT where they build tracks on 24 targets within a few seconds. Watching that video again and just eye-balling it, the targets detected encompass about 90° FOV with just under half beyond 60nm. This might suggest that the inner range FOV depicted on these graphics are off by a factor of at least 2.
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