The Helix ASW nightmare

[gregb41352]

Ok, admittedly I'm sort of new to this but I have a question.

I have a Seawolf class SSN trying to infiltrate a Chinese carrier
task force. I also have some Poseidons on surveillance in the
distance. I'm as deep as possible at creep speed. These Helix's
just drop torps on me like I'm on the surface radiating to high
heaven. No matter what I do these &%&(* Helix's find me.

What am I doing wrong or missing here?

Thank you.

[ShadowB]

Here's some insight on how the various depth levels affect ease of detection. Going deep isn't necessarily the best idea (at least unless you're hugging the sea floor), and sometimes it's even the worst if you're up against surface sub hunters trailing towed sonar arrays, which hang just below the thermocline layer and can potentially hear your boat unimpeded.

ORIGINAL: AndrewJ (post here)

There are a number of items about CMANO's sonar model that might be helpful for your hunting. Here's what I discovered after some trials a few months ago.

The uppermost part of the ocean (anything above 50 m) models the surface duct. Sonar performance is very good in the duct, so a quiet sub can hear other contacts that are also in the duct at good distances. Of course, they can hear you too, so if you are moving at speed (where you will cavitate easily due to the shallow depth) then you might find yourself detected too soon. If you want to listen here with your conventional sub, then make sure you manually set your depth below periscope depth, otherwise your diesels will turn on and take away some of your stealth advantage.

The lowest part of the ocean, beneath the layer, is the deep sound channel. Sound transmission there is excellent - even better than in the surface duct. Go there to listen if you like, but be very quiet, because anyone else down there will have a good chance to hear you too.

Sound transmission into the layer from above or below is poor, sound transmission across the layer is worse, and sound transmission within the layer to another target in the layer is worst of all.

So it might seem like the best way to hide from surface ships is to put yourself beneath the layer, yes? Sometimes it is, but be very careful who you try to play this trick against. Almost all modern sub hunters will have a variable depth sonar (look for 'VDS' in the sensor list) and that's being towed around below the layer. So now, instead of hiding, you're sharing the deep sound channel with a powerful hostile sensor. If you have been operating down there against a VDS equipped foe you've actually been putting yourself in the worst possible position. They can hear you just fine, but you can only hear them faintly through the layer. The best compromise against a surface group is often to manually put yourself within the layer, to stay out of the deep sound channel, but still get some protection from direct detection from above. You can make brief forays above and below the layer to listen, and then return to it to hide. Only stay down there if you're certain they don't have a VDS.

One advantage to a submarine with a towed array is that it can cruise along within the layer, and the array will act as though it is below the layer, allowing you to listen into the deep sound channel for anyone who might be down there, as well as allowing you to listen back up into the layer, which is better than listening along the layer.

If the water is deep enough to allow convergence zones (those broad pale green rings) then you will get a great increase in sonar range, but only on the pale green rings themselves. Between the outer rings you have no effective sonar, and your direct path detection will not usually allow you to detect all the way to the first ring. So if you need to do any sprinting against a known target, then do it while you are between rings, and slow down when you must cross a CZ, or you are at risk of being detected.

The sonar model also takes into account the reverberation problems from the sea floor when active sonar is in use. You can get very significant reductions in active sonar detection range by hugging the sea floor in shallow water. For example, a Udaloy blasting away with its powerful Horse jaw active sonar can detect an SS in deep water at 10 miles (15 in the surface duct, or even 25 at side aspect if the surface duct CZ kicks in), but if you're hugging the sea floor 100 m down he'll only see you at just over 1 mile. That can be a massive tactical advantage, and is why conventional subs are such a problem in the littoral.

[Cik]

as shadow noted, depth is not really a real defense against modern sonobuoys or dipping sonars(?) at least, it's never seemed like it was to me.

your best bet if you want to kill ASW ships is to crawl, and i mean REALLY crawl (1-2 kn) in the layer into their patrol box (if they are patrolling, at least. if they are simply moving from A-->B then you may be SOL) and then stop your screws, periodically popping above the layer (VERY BRIEFLY) to keep a rough track of them via passive sonar.

once the ship gets very close to you, jam a dozen torpedoes into it as fast as possible, then run and hope the helix doesn't find you.

logic indicates to me that hunting something designed to hard-counter you seems like a foolish gambit, and the simulation pretty much bears that out. how do you defeat a modern ASW-heli equipped ASW destroyer with a sub? with great patience. it's possible to win, but even then not terribly reliably. most of the time you're going to achieve a mutual kill at best- you sink the heli's platform and then you get iced by the helo as it comes to the torpedo's origin to wreak it's terrible vengeance.

but yes, i'd say stay in the layer and stay slow if you want any chance. shallow is suicide, and against certain equipment, so is deep.

[gregb41352]

Thanks for the great replies guys.

[Primarchx]

Great advise so far. Running subs against a credible ASW force is difficult. Parking somewhere in a strong thermocline and using very moderate speeds (only go as fast as you absolutely have to go) seems to be the best approach.

One tactic I use is when I've established a contact, hopefully with a little TMA to get a feel for where it's going, I'll position myself in the thermocline band in such a way that I lose sensor contact with the target with the idea being if I can't see them they will probably have a hard time seeing me. I then carefully scoot to a spot along the intercept path, slow down and see if I can reestablish contact then go from there. Sometimes during those transits the target will become heard again and I have to readjust depth or back off.

Active sonar is real PITA, too. A good set will often reveal your sub outside your best torp engagement range. The best approach here is to position yourself in/under the thermocline until you can't hear the sonar, then move to intercept. There are VDS active sets and of course active dipping sonars that can go under the layer, though, so you have to be careful along with usual precautions for passive sonar detection. If you are moving in a ship's active sonar range and can hear its' pings you are very likely detected. For a high percentage torp shot against an active emitter you often have to accept that it's going to see you as you get your fix on it for the attack (moving to periscope depth or accurately tracking it acoustically). Be prepared and have sea room to evade.

It's a real cat-and-mouse game which can end abruptly if the target gets a whiff of you. There are times you have to give up because the geometry is no good, either, requiring you to go too fast to intercept the target and likely betraying your position.

[ShadowB]

All that said, when it comes to torpedo evasion, is CMANO really realistic?

Subs don't seem to use decoys too often (it's automatic-only, as far as I know), and you'd think leaving a couple as you dash up and down the layer should give you some chance of confusing the seeker. Also, at least in my limited experience, torpedos are detected fairly late into their run, reducing reaction time (perhaps I've mostly faced the ASROC or air-dropped variety, though). Are modern sub countermeasures really that ineffective or has the game taken a pessimistic estimate based on the available declassified material on the subject?

[Cik]

it's hard to say on the tech level, but generally at equal technology things usually favor the attacker. you can still survive if you are a little lucky.

also personally i've never had problems detecting torpedoes. usually i detect them right as they enter the water, the problem being that they enter the water right above me and kill me in <15 seconds. i sure do know however, that whenever i fire a spread at something with a passive sonar it detects them IMMEDIATELY. my bet is that the same is the case if they fire them at you from a ship or sub. torpedoes are probably relatively noisy, and they travel at an easily detectable band of water as far as i know.

[mikmykWS]

Best advice is don't get caught and gamble when the geometry makes sense for a high percentage kill. Once your spotted the gig is up.

https://m.youtube.com/watch?v=fOEQTJV_3-w

[wild_Willie2]

Hi Cik,

You can manually set your torpedoes to slow speed and have them move within or below the layer in order to make them harder to detect...

W.

[Bert Blitzkrieg]

ORIGINAL: wild_Willie2

Hi Cik,

You can manually set your torpedoes to slow speed and have them move within or below the layer in order to make them harder to detect...

W.

But only, as far as I know, AFTER you've fired them.

[Cik]

ORIGINAL: wild_Willie2

Hi Cik,

You can manually set your torpedoes to slow speed and have them move within or below the layer in order to make them harder to detect...

W.

i don't know much about torpedoes, is that actually realistic? i mean, you have a wirelink to most of the NATO ones as far as i know so technically it's possible(?)

the real question though is why the default behavior is to run the shallow sound channel considering that's the worst possible decision if you don't want to be harpooned by your local helix.

which i guess is why it always seemed unrealistic to me. if you were meant to be able to have them in the layer, there's no reason to have them anywhere else except when they are on terminal attack. am i wrong?

[Bert Blitzkrieg]

ORIGINAL: Cik

ORIGINAL: wild_Willie2

Hi Cik,

You can manually set your torpedoes to slow speed and have them move within or below the layer in order to make them harder to detect...

W.

i don't know much about torpedoes, is that actually realistic? i mean, you have a wirelink to most of the NATO ones as far as i know so technically it's possible(?)

the real question though is why the default behavior is to run the shallow sound channel considering that's the worst possible decision if you don't want to be harpooned by your local helix.

which i guess is why it always seemed unrealistic to me. if you were meant to be able to have them in the layer, there's no reason to have them anywhere else except when they are on terminal attack. am i wrong?

I'm no torpedo expert either, but technically it is possible to guide your torpedo anyway you like. So, ideally, you should be able to "program" the torpedo(es) before you launch them. I believe that is how it is done for real.