Passing thermal layer and DC's attack?

These are two questions:
1. Passing thermal layer makes me invinsible to passive sonar at ahead slow or with silent running? Is it working for real or it is just for show?
2. When under attack by destroyer, what is the best evasion tactic?

[NefariousKoel]

1) Yes it is in. I have noticed that some of my more distant contacts were lost after passing the layer. However, it won't make you invisible. At least, it shouldn't. Enemy destroyers should still be able to detect you, but they have to be much closer to you than normal.

[daft]

Don't know any definitive answers to any of your questions, but I usually wait until the destroyer is almost on top of me and starts speeding up for his attack run. I ring up flank speed and and give a little rudder to either side of his path (depending on the angle of his run) to get out of the kill zone. As soon as things settle down after the detonation I slow down, go to silent running and creep a little deeper depending on how close the ash cans came.

But when you are at ahead slow, what the good use of decoys?

[daft]

Originally Posted by GakunGak

But when you are at ahead slow, what the good use of decoys?

I've never used the decoys in SH4 so I don't really know how effective they are yet.

Originally Posted by Henric Edwards

I've never used the decoys in SH4 so I don't really know how effective they are yet.

What I really meant was what the good use when you have to be far away from them, and when you speed up, destroyers will hear you anyway....
So, to not being heard at all is the all-stop ring?

[RedHammer]

That`s why, as previously explained, when far away, fire decoys, run silent, go deeper. Just keep away from those deadly ash can`s until those DD`s are empty of them.


S! to all

Your Friend in the Pacific

RH

[Dowly]

Originally Posted by GakunGak

But when you are at ahead slow, what the good use of decoys?

There´s two ways how I use the decoys. If the DD is close, I fire one up go to flank speed for a 2-3 seconds and change my depth. But if the DD is far away, like if I am leaving a port which I raided just moments ago, I fire up the decoy and continue on silent run.

[PeriscopeDepth]

The layer certainly causes some transmission loss, but does NOT make you invisible IRL in most cases.

PD

[Cobra_mkII]

Originally Posted by GakunGak

These are two questions:
1. Passing thermal layer makes me invinsible to passive sonar at ahead slow or with silent running? Is it working for real or it is just for show?
2. When under attack by destroyer, what is the best evasion tactic?

Just to prove the layer is modelled-
Flavoured to Taste modified the thermal layer:

"/DATA/CFG/SIM.CFG
------------------------
- ai cannons max fire range from 6K to 9K
- Ai cannons / Max error angle from 3 to 4
- lost contact time from 15 to 30 mins
- visual / enemy surface factor from 400 to 150
- visual / enemy speed factor from 15 to 9
- Visual / light factor from 1.0 to 2.0 (2.0 to 1.75)
- hydrophone / sensitivity from 0.03 to 0.04
- hyrophone / waves factor from 0.5 to 0.95
- hydrophone / noise factor from 1 to 0.35
- hydrophone / thermal layer attun from 3.0 to 2.0
- sonar / detecton time from 20 to 10
- sonar / thermal layer attun from 5.0 to 4.0"

So run silent run deep

If I have been detected I run and dive at flank, just before the thermal layer I launch a decoy, switch to silent running and turn away. My flank speed will allow me to drift away from the decoy (which is above the thermal layer) while I creep away below it.

[TheSatyr]

I creep beneath the layer. If I get dropped on I go to flank and get out of the way,then start creeping again once the noise from the DCs settle down. I never use decoys since the US subs never had them in WW2...including them in the game is one of my biggest beefs with the game...completely un-historical and un-realistic. (Sort of like having Lancasters with upside down US markings...heh).

Course if I'm caught in shallow water my tactics change. I still creep but I try to keep heading towards deeper water. And when I go to flank when I get dropped on I keep my course heading towards deeper water and hope the DCs drop behind me.

[Farinhir]

The reason you become more difficult to detect under a thermal layer is because sound travels at different speeds with different pressure and temps in the water. This along with the cylindrical spreading and signal absorbtion from the layer make it harder to find a sub that is under a thermal layer. There are more factors that would cause this. One is the fact that sound likes to bend in a path that will allow it to move slower. Another is "Ray Propagation Theory". Sound in water can be represented as a vector or ray.

Ray Propagation Theory states that:

1: RAYS will change direction when passing through two mediums of different density. This is Snell's Law. Crossing a thermal layer would count as passing through two mediums of different density.

2: Sound will bend towards the region of slower sound speed.

Because of these factors, when you cross a thermal layer you can find that most of the area is a shadow zone.

A good source of information on this is a powerpoint found on Berkley's navsci area (something I stumbled upon). Most of my information is from there.

Source PPT:
http://navsci.berkeley.edu/ns401/NS4...ound%20mjh.ppt

Read the instructor notes that were included with the slides. They give a lot more info.

CHeers,
~F~

@Farinhir: THNX for the link, ya rule!!!!!!!

[STEED]

I know one thing I am sick to death every so often setting out on patrol hearing about every ten seconds Passing thermal layer in that robot voice.


Moving on, when I attack a convoy on silent running nice and deep and if all is in place I slowly come up to have a look and make my final decision.

[tycho102]

Originally Posted by GakunGak

These are two questions:
1. Passing thermal layer makes me invinsible to passive sonar at ahead slow or with silent running? Is it working for real or it is just for show?

2. When under attack by destroyer, what is the best evasion tactic?

1. In the stock game, it attenuates sound by something like 30%. Several mods change this down to 20% or less.

2. Dive as deep as possible. Run at 1kt when they're right over you, 2kts when they've moved off a little bit, 3 or 4 knots when you can. Your best best is to always dive at 4 knots just after firing a salvo, and turning ninety or more degrees to take you away from the firing position. Once you get some depth (60+ meters) and the torpedoes have impacted, reduce speed as the destroyers close in. You are better off using approach and attack configurations which don't put you in the position of being detected. The "dead stick" approach works in every case I've used it, in deep water.