[WAD] Sonar and ASW Question

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[WAD] Sonar and ASW Question - 5/22/2018 12:54:39 AM

kvnjnny

Posts: 14
Joined: 12/3/2014
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Hello!
I am trying to get a better handle on ASW operations. Inspired by Baloogan, I created a basic scenario to evaluate the Oliver Hazard Perry class frigate and the AN/SQR-18A towed sonar array. The OPFOR consists of a single Sierra I (PLA-945) and three Victor III (PLA-671RTM) circa 1988. No combat, just detection

I have the subs steaming parallel courses about 40nm apart at different speeds and different depths to determine how well the towed array can make a detection.

The Perry is sailing perpendicular to the subs, sprint and drift with only the towed sonar in use.

Clear weather, calm seas.

I have run it a couple of times, but the results are surprising disappointing for the AN/SQR-18A. It might detect something if it is within 15nm, but just a frequently does not. I literally watched the Sierra pass undetected at 15 plus knots, depth 130ft, cutting across the Perry's course at less than 1.5 km - no detection! This was coming off a sprint where the Sierra was doing close to 30kts at periscope depth at a distance of between 10 - 20km.

This just doesn't seem right. Either the AN/SQR-18A is garbage (which it wasn't), or the Soviet subs are really quiet or I just don't know what I am doing.

Thanks for the feedback!

< Message edited by Dimitris -- 6/2/2018 4:09:52 PM >

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RE: Sonar and ASW Question - 5/22/2018 2:17:33 AM

Raptorx7_slith

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You need to post a save.

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RE: Sonar and ASW Question - 5/22/2018 2:40:25 AM

kvnjnny

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Thanks!

Attachment (1)

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RE: Sonar and ASW Question - 5/22/2018 3:04:37 AM

kvnjnny

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Joined: 12/3/2014
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Just ran another test:

Sierra #1 is moving at 13 kts at depth of 131 ft. Distance to Perry is 10nm.

Victor III #1 is moving at 22 kts at depth of 66 ft and cavitating. Distance to Perry is 9.6 nm.

The Perry has both the AN/SQR-18A (TASS) and the AN/SQS-56 operational. Both targets are dead ahead.

No sonar contact by the Perry.

Is this possibly a glitch?

I'll try the same test with a Spruance and a Burke to see what results.

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RE: Sonar and ASW Question - 5/24/2018 6:41:25 AM

CptRoss

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Joined: 5/21/2018
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I don't have a solution, just can confirm the behavior using version xxx Build xxxx that

#Sierra 1 only gets detected when its cavitating at 35kts -133ft and the range is within 6nm but reported estimated 14nm

I tried the #xxxx - D 644 Primauguet Type F70 xxxx with same disappointing results.

--- I am using xxxx to show moderators that I cannot post numbers because it says that I am not allowed to post links or phone numbers. Great. Thanks.

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< Message edited by CptRoss -- 5/24/2018 6:43:09 AM >

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RE: Sonar and ASW Question - 5/24/2018 7:53:46 AM

Dimitris

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Before looking at this at depth..... are the target subs over or under the layer?

Towed arrays deployed by ships are always streamed under the layer, so they will have much better performance against subs likewise under it than those over it, particularly if the layer is "strong".

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RE: Sonar and ASW Question - 5/24/2018 8:56:40 AM

CptRoss

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Joined: 5/21/2018
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Thank you for the info Dimitris.

I tried two versions.

First run: Under the layer.
One sub detected.
Second sub slipped through.

Second run: Over the layer.
Both subs slipped through.

Kvnjnny I attached a zip with saves and videos. maybe it helps.

Conclusion: Perry Class or Spruance Class Ships are quite defenseless against subs over the layer or in shallow water?!

Attachment (1)

< Message edited by CptRoss -- 5/24/2018 9:09:53 AM >

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RE: Sonar and ASW Question - 5/24/2018 10:51:12 AM

Rory Noonan

Posts: 2816
Joined: 12/18/2014
From: Brooklyn, NY
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quote:

ORIGINAL: kvnjnny

Just ran another test:

Sierra #1 is moving at 13 kts at depth of 131 ft. Distance to Perry is 10nm.

Victor III #1 is moving at 22 kts at depth of 66 ft and cavitating. Distance to Perry is 9.6 nm.

The Perry has both the AN/SQR-18A (TASS) and the AN/SQS-56 operational. Both targets are dead ahead.

No sonar contact by the Perry.

Is this possibly a glitch?

I'll try the same test with a Spruance and a Burke to see what results.

Hi kvnjnny,

Thanks for the save file. The issue you're running into is the sensor fit on this breed of Perry FFG and the quietness/depth/speed of the submarines you're attempting to detect.

The Perry we're concerned with has an AN/SQS-56 bow sonar (range 5nm, operates above the thermocline) and an AN/SQR-18A towed array (range 40nm, operates primarily below the thermocline when used by surface ships).

At the moment the Perry's towed array is sitting below the layer (which is quite strong at 0.42), so any sound from the Sierra is going to have to go through the layer to get to the towed array. The bow sonar is out of range and won't detect the Sierra no matter what.

The Sierra is also a very quiet submarine, every bit as quiet as the Akula. The main reason it didn't go into production was because of the price of titanium. At the moment of the save you provided it's coming off a sprint, so the powerplant noise (which is the primary determinant of noise, the other being flow noise) is very low and while the flow noise at 14kt is significant it is not enough to get through the layer--it's also constantly decreasing as the Sierra slows down after its sprint.

Trying it with the Sierra below the layer at -120m in the exact same position and exact same speed (i.e. using Lua to change the depth) results in the Sierra being detected almost immediately.

Hope that answers your questions.

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#1256 - F 182 Babur [Type 21 Amazon Class] (Pakistan - ... - 5/24/2018 11:35:37 AM

CptRoss

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Apache, I tried to use the #1256 - F 182 Babur [Type 21 Amazon Class] (Pakistan - 2000) instead of the Perry and only selected the ATAS(V)1 as a sensor. Because what you wrote I would have expected different results than the Perry class (did not try the LUA Script I am to noob for that).

ATAS(V)1 Range Max: 74.1 km
AN/SQS-56 Range Max: 9.3 km

I was using the Babur because I played "Uncle Mark's Tutorials - 6 - Toledo Hits 'Em Hard, 2004" (Link) and it was quite some work not to get detected.

< Message edited by CptRoss -- 5/24/2018 12:05:19 PM >

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RE: #1256 - F 182 Babur [Type 21 Amazon Class] (Pakista... - 5/29/2018 6:24:06 AM

Dimitris

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CptRoss < Is there a question? I'm not sure I understand your point, please clarify.

Both sonars have a bind zone between the direct-path limit (9.5nm nominal, varies in practice) and the first CZ ring.

< Message edited by Dimitris -- 5/29/2018 8:00:57 AM >

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RE: #1256 - F 182 Babur [Type 21 Amazon Class] (Pakista... - 5/29/2018 1:33:42 PM

kvnjnny

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Joined: 12/3/2014
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Thanks to everyone for looking into this! It seems that the game is functioning (modeling) correctly. However, this raises the question: are surfaces vessels more vulnerable to submarines that are less than 12nm distant and shallow? It seems that the Perry should have easily detected the Victor III even without a towed array - "Victor III #1 is moving at 22 kts at depth of 66 ft and cavitating. Distance to Perry is 9.6 nm."

When I substituted a Spruance common to that period, the Spruance performed better but still had trouble close in. Same conditions, just substituted surface vessels

Some preliminary conclusions:
1) The Perry class frigate or more accurately, the AN/SQR-18A (TASS) and the AN/SQS-56 sonars, are pretty poor escorts, Tom Clancey's writings not withstanding.

2) Active Sonar is fairly useless. It only broadcasts one's position at great distance and doesn't really add to detection value. - Once again this doesn't seem quite right; the analogy usually given is of throwing on a bright light in a dark room. Yes, the one with the light is now visible to everyone but everyone else in the room is also visible. The game modeling seems to suggest that instead of a bright light, someone strikes a match which gives a bit of illumination but mostly just tells everyone where you are - so why even strike the match or carry it?

3) Towed sonar arrays are of marginal improvement over hull mounted sonars - you may or may not detect subs and if you do, the best course of action is to get the ships out of there and pounce the pig-boats with helos!

4) Sonar is not Radar - radar "sees" everything in the sky within its ranges (discerning what it is, that's different); sonar does not "hear" everything in its effective range

I will keep running some trials with different variables.
Cheers to everyone who develops and contributes to CMANO! It is the finest sim on the market!

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RE: Sonar and ASW Question - 5/29/2018 3:23:27 PM

kvnjnny

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Apache85, I just wanted to confirm your data. I checked my copies of Ships and Aircraft of the US Fleet (14e) and Combat Fleets of the World ('88/89) on the Perry class. I haven't had a chance to check Friedman's U.S. Destroyers yet.

The Perry was fitted out with the low performance SQS-56 bow sonar has a cost saving measure (thanks Congress

). The intention was that the FFG-7 frigates would rely primarily on their SQR-19 TACTASS (towed array) and helos from ASW work. The SQS-56 seems to be a last-resort backup. Delays in getting the SQR-19 led to the installation of the SQR-18A temporarily. Combat Fleets of the World identifies FFG-38, -48, -55, -56 and -60 has having the SQS-56/SQR-18A configuration in 1988/89 whereas all others were upgraded to SQQ-89(V)2 ASW suite consisting of the SQS-53B hull sonar and SQR-19 towed array. FFG-7s assigned to the Naval Reserve Force were updated when possible.

It seems that not all Perry's are equal! I picked the junior varsity to run my tests on. I will run it again with the main line fleet version for 1988 and check the results.

I love the detail this sim goes into. The developers really did their research in putting this thing together!

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Post #: 12

RE: #1256 - F 182 Babur [Type 21 Amazon Class] (Pakista... - 5/30/2018 1:55:59 AM

Rory Noonan

Posts: 2816
Joined: 12/18/2014
From: Brooklyn, NY
Status: offline

quote:

ORIGINAL: kvnjnny

Thanks to everyone for looking into this! It seems that the game is functioning (modeling) correctly. However, this raises the question: are surfaces vessels more vulnerable to submarines that are less than 12nm distant and shallow? It seems that the Perry should have easily detected the Victor III even without a towed array - "Victor III #1 is moving at 22 kts at depth of 66 ft and cavitating. Distance to Perry is 9.6 nm."

When I substituted a Spruance common to that period, the Spruance performed better but still had trouble close in. Same conditions, just substituted surface vessels

Some preliminary conclusions:
1) The Perry class frigate or more accurately, the AN/SQR-18A (TASS) and the AN/SQS-56 sonars, are pretty poor escorts, Tom Clancey's writings not withstanding.

2) Active Sonar is fairly useless. It only broadcasts one's position at great distance and doesn't really add to detection value. - Once again this doesn't seem quite right; the analogy usually given is of throwing on a bright light in a dark room. Yes, the one with the light is now visible to everyone but everyone else in the room is also visible. The game modeling seems to suggest that instead of a bright light, someone strikes a match which gives a bit of illumination but mostly just tells everyone where you are - so why even strike the match or carry it?

3) Towed sonar arrays are of marginal improvement over hull mounted sonars - you may or may not detect subs and if you do, the best course of action is to get the ships out of there and pounce the pig-boats with helos!

4) Sonar is not Radar - radar "sees" everything in the sky within its ranges (discerning what it is, that's different); sonar does not "hear" everything in its effective range

I will keep running some trials with different variables.
Cheers to everyone who develops and contributes to CMANO! It is the finest sim on the market!

All valid conclusions. Active sonar is useful in shallow, confined waters when hunting subs and also when a sub is detected at short range to firm up a firing solution. They very likely already know where you are in those cases so there's not much of a trade-off and the bonus is that you may detect and localise them before they're in a firing position.

Towed arrays are pretty good but not all towed arrays are created equal.

There's a lot of variables with passive sonar, if you're making lots of noise yourself (i.e. moving fast) it degrades your performance, also if there's something noisy along the same bearing as a sub you probably wont be able to pick the sub out from the background noise.

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