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Radar modes question


john4pap

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I hope you will excuse my noob question but I've read the manual once and I'm on the second run of Chuck's guide and I still don't follow: I understand the TWS part but I don't get what RWS is and how it's supposed to differ from TWS. I'm also at a loss re RWS' submodes (if I'm not mistaken) SAM and DTT.

 

On a slightly different matter I'm confused by a statement in Chuck's guide (p.181) which I believe is also to be found in the manual:

 

"CRM mode is selected by default at power-up. It is designed to reduce pilot workload by combining air-to-air submodes used for search under one interface."

 

What confuses me here is the word "combine". I understand that I may select either TWS OR RWS in BVR (or else CRM)... but a combination?

 

Could someone offer a clarification on the above?

 

 

 

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Combined Radar Modes (CRM) is the term for the group of AA radar modes which are presented "top down". The alternative is ACM which is the group of all visual radar modes. All AA radar falls into one of those two categories.

CRM includes: RWS, TWS, VSR, LRS

Range while scan (RWS) is the baseline radar that shows targets as contacts which is positional information. This is in contrast to track while scan (TWS) which produces tracks which are positional plus motion.

SAM/DTT are simply RWS with one or two tracks one of which is the target of interest "bug". SAM/DTS doesn't really apply to TWS. TWS with a bug would be similar to SAM and dual-target-track doesn't apply because TWS can have 10 tracks so having "bug plus one" isn't a feature.

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TWS can have more than 10 as well. The TWS limit is 10 system tracks. The tank tracks have a much higher limit. I don't know what the RWS contact limit is, if any, but it would be higher still.

RWS has benefit over TWS in terms of track quality when in the SAM/twoSAM submodes. AIM-120s employed against a SAM bugged target will have a higher Pk as the radar has a more accurate understand of the target(s). TWS as described to me by an active pilot is "so bad we don't use it." TWS is the only mode which 3 or more simultaneous targets can be engaged by AIM-120. There are other details like SAM has continuously-variable azimuth limits (up to the 60/30/10 limits) depending on the situation. TWS is simply 60/25/10 static. In some versions of the radar TWS is unable to select 160nm range suggesting its performance was poor.

The biggest practical difference is that TWS shows maximum tracks and RWS dwells on tracks of interest. Dwelling improves track quality of the targets the radar dwells on at the risk of alerting those targets they are more than painted.

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Many thanks for your answer. So TWS is a mode that should be avoided unless needing to fire to more than two targets. This sounds quite odd since in the manual it reads like TWS is the most sophisticated mode judging from all the different contact types it contains.

What would you mean by continuously-variable azimuth limits as opposed to static? I mean I can change the azimuth in either mode...
Also I am still perplexed about what you mentioned in your previous reply about non-bugged contacts in either RWS and TWS. In either mode I see small squares with a line protruding indicating their course. How is one just contacts and the other one tracks with motion.

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If TWS performs adequately in the sim then use it I guess. I was surprised that it's not thought highly of in reality (and this is only one source). RWS with a bug was always going to have better quality on the bug than TWS simply by how it works. The "tank track" level wasn't always a feature of the radar historically. Originally it was just the 10 tracks. I would agree TWS is pretty sophisticated but by getting information on a lot of targets the average quality is reduced.

The little blue azimuth lines in SAM should grow and shrink based on the geometry of the situation. The radar is doing two things in SAM, a quick series of updates on the bugged target and then a scan of the space around the cursor. By separating the scan space from the bug or the bugged target gets closer or there are two tracks all of these cause the radar to have less time to devote to the second-priority search task and the search area shrinks. With one well-behaved SAM bug far away the radar can scan the full +-60 azimuth. At closer range the azimuth limits start to shrink. With say the target to the right and the scan zone to the left the radar has to shrink even more because the radar spends time moving the antenna. At close ranges the search portion has to be abandoned entirely and SAM looks similar to STT.

Contact is a one-time position return. It will be a small filled-in box. On top of this box is a "hot line" which is the radial velocity information due to the Doppler color of that return. When a wave bounces off an approaching target the frequency is increased and receding decrease. If the frequency is blue or red shifted (and by how much) tells the radar the velocity of the target but only in the radial direction which is why the hot line is only vertical in the scope. It's like taking a photograph of a school bus and knowing if it was coming at you or backing up because it was a little redder or bluer than its normal color in the picture. You can't tell how left-to-right it was going. It's not a trend over a history of several pictures but an actual measurement taken from a single snapshot.

Tracks require at least two detections. The radar detects the target once and then again, decides they are the same object, and draws a line from the first detection to the second. This is why the vector line on a track can be in any direction.

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An F-16 instructor once told me (concerning TWS vs Dual Target SAM), "If we ever have to shoot more than two people at once, there are bigger problems in the Pentagon." Another F-16 instructor told me "always always RWS, never TWS."

The one scenario where i see TWS being useful is on a defensive counter air against a lot of bombers. Against fighters, RWS with DTS, gives your flight enough of a chance to whittle down your enemies on a launch and leave, that you can then turn back in and pick off the survivors as you go to the merge (shooting survivors all the way in).

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Dances, PhD

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On 2/17/2022 at 5:36 AM, TheBigTatanka said:

An F-16 instructor once told me (concerning TWS vs Dual Target SAM), "If we ever have to shoot more than two people at once, there are bigger problems in the Pentagon." Another F-16 instructor told me "always always RWS, never TWS."

The one scenario where i see TWS being useful is on a defensive counter air against a lot of bombers. Against fighters, RWS with DTS, gives your flight enough of a chance to whittle down your enemies on a launch and leave, that you can then turn back in and pick off the survivors as you go to the merge (shooting survivors all the way in).

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Might be different for other nations that use F-16 as A-A platform. Nevertheless, in DCS, TWS is equally as good as SAM (or even better since it updates target location continously, SAM or DTT has a few second lag visible on the TD box). 

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