Depth-charge turbulence

[Floater]

Correct me if I'm wrong, and apologies if this has been discussed before, but:

In a recent depth-charge attack, I confirmed what I'd been suspecting for a while: that the DDs' sonar isn't affected by the turbulence created by recent depth-charge explosions. This is very disappointing, since it was a crucial factor in ASW operations, and also crucial for evasive manouvers by the sub.

For those that don't know, the detonation of depth-charges cause so much turbulence that all sonar (ASDIC and hydrophone) operations were impossible for several minutes. Captain Donald MacIntyre - an ace ASW destroyer captain and ASW group leader - says in his memoirs (U-boat Killer) that it took about 15 minutes for them to regain sonar capabilities after an attack.

A common evasive manouver for the U-boat (and for other nations' subs) was to travel at highest speed on a new course, unconcerned about noise, for a few minutes after explosions and then return to silent running some distance away.

In this recent attack, I used this tactic after a nearby depth-charging, and another DD, which was starting an approach from behind, matched my manouvres. I turned starboard, so did he. I turned port, and he did the same. This was a co-ordinated attack - a third DD was stopped and listening.

This aspect was modelled in SH2 - I think it's a 10-minute blindness there - so it's sad to see that it's been omitted from SH3, especially when other, much more complex ASW operations are done so well, such as the Johnny Walker Creeping Attack which I was subjected to.

Your thoughts on this?

[the_rydster]

This aspect was modelled in SH2 - I think it's a 10-minute blindness there - so it's sad to see that it's been omitted from SH3, especially when other, much more complex ASW operations are done so well, such as the Johnny Walker Creeping Attack which I was subjected to.

What is the Johnny Walker Creeping Attack?

I assumed that ASW operations were impaired after a DC attack. If the developers have missed this it is a bit of a screw up really.

Shame that as games get PC's get more powerful games have to be simplified in some ways.

[welshterrier]

Im sure there is a mod possibility in there somewhere if its true :-P

[CB..]

i agree john! even with one lone destroyer -if i go to flank immediately the DC's explode -after less than a minute -(unless i slow down)- i will hear the we have been detected message- more often than not..which with a lone DD is pretty conclusive evidence that he isn't at all hampered by the aftermath of the explosions...bit weird...

[Deamon]

In a recent depth-charge attack, I confirmed what I'd been suspecting for a while: that the DDs' sonar isn't affected by the turbulence created by recent depth-charge explosions.

And it never was affected in all the WWII sims when i remember right.

This is very disappointing,

I tell ya.

For those that don't know, the detonation of depth-charges cause so much turbulence that all sonar (ASDIC and hydrophone) operations were impossible for several minutes.

And the bubble clouds left in the water for a time gaved asdic returns and allowed the u-boat hide behinde it. The u-boats also liked it to creep away using the DD's wake to hide.

Nothing of it is modeled in all thous sims. But you can bet that i will model it in mys :)

Captain Donald MacIntyre - an ace ASW destroyer captain and ASW group leader - says in his memoirs (U-boat Killer) that it took about 15 minutes for them to regain sonar capabilities after an attack.

15 minutes ? That's quite long. Were the sonars realy washed out for 15 minutes ?

This aspect was modelled in SH2 - I think it's a 10-minute blindness there -

Are you sure about it ? I'v never noticed that it was modeled in SHII. The DD's always come right above me after eatch run.

Deamon

[Floater]

What is the Johnny Walker Creeping Attack?
Basic idea: you need two or more DDs. One sits still, or moves very slowly, tracking the sub. The other, directed by radio from the listening DD, approaches at DC speed from the stern of the U-boat, in its baffles (blind spot), the DD getting pretty close to the U-boat's location before its own engine noises swamp the sonar on the listening DD.

Capt. Johnny Walker, probably the best of all the ASW leaders, came up with the idea and, if you've got more than one DD, it was a extremely successful tactic, and became used by all ASW groups as the war progressed.

[Floater]

@Daemon:

Glad to hear you'll be modelling it in your own sim. It's details like that that can make a huge difference to tactics and realism.

I'm 99% sure that Macintyre said 15 minutes, but without reading the book through I can get 100%. And if he says it, it's true. ;) I must admit I was surprised at how long it took for the turbulence to clear, but then I'm no expert in hyrdodynamics.

As for SH2, I think it was Mark Kundinger (sp?), one of the dev team who used to post on the Subsim forums, who said it was set at, or maybe around, 10 minutes. I used to use that blind period for a change of course and flank speed, and it was a very successful tactic. So, I do believe that the blindness period was modelled.

[the_rydster]

Cool!

I thought it was some sort of reference to the whisky or something??

[Col7777]

That's the spirit rydster, :)
On the opposite note I think the silent running is a lot better in this sim, it wasn't much use in SH2, I tend to use that tactic and creep away IF possible 9 times out of 10.

[Floater]

That's the spirit rydster, :)
On the opposite note I think the silent running is a lot better in this sim, it wasn't much use in SH2, I tend to use that tactic and creep away IF possible 9 times out of 10.
Heh! Yes, indeed. Once, in a single mission, I tried to use the high flank speed of a XXI to escape a DD pursuit. They were using the Johnny Walker tactic - or maybe it was White Horse, or Bells, or Glenmorangie, or Glenfiddich ... :D

Anyway, I couldn't escape even at flank, since the listening DD still had me pinned down. I got away in the end by going silent and slow and deep, with many turns around a general heading, and that seems to the best all-round tactic. In SH2, the sprint would have been enough to get out of range, and the slow, silent running tactic would probably have ensured my quick death.

One thing that isn't modelled in either sim - and I'm not blaming the devs, because it would be very difficult to do - is intelligent prediction of the target's likely course.

When I was under attack in Loch Ewe, I was desperate to get out. I was still OK for batteries - I'd been doing 1kt all the time - but the oxygen was getting low, so there was only one route I was going to try. In real life, I'm sure the ASW team would have realised that (I'd never had chance to surface undetected) and stationed themselves at the outer bottleneck, listening, with maybe one DD keeping near to the U-boat to make sure I didn't try to surface.

Maybe in ten years, with more powerful computers and programming techniques, we'll see AI that'll think that hard.

[Col7777]

RE the AI thinking that good, I'm sure you are right John.

I bumped in to a convoy last night with what looked like only 3 escorts. I crept passed the lead escort completely unnoticed. Then I managed to get a few tasty targets and I was creeping away, the escorts carried on as if nothing was happening so I turned for another go and managed 2 more then decided to leave.
Only then did 2 of the escorts make a weak search then rejoined the convoy, I left for safe open waters.

[Deamon]

@Daemon:

Glad to hear you'll be modelling it in your own sim. It's details like that that can make a huge difference to tactics and realism.

Oh yes. I'm a hydroacoustics nut as well, you maybe know this, so i want to model the hydroacustical engine very ditailed.

I'm 99% sure that Macintyre said 15 minutes, but without reading the book through I can get 100%. And if he says it, it's true. ;) I must admit I was surprised at how long it took for the turbulence to clear, but then I'm no expert in hyrdodynamics.

Well, 15min washout seem to be a little bit to long. So the question here is what he mean, 15 minutes to let the washout pass and redetect the target or 15 minutes to pass the washout ?

As for SH2, I think it was Mark Kundinger (sp?), one of the dev team who used to post on the Subsim forums, who said it was set at, or maybe around, 10 minutes. I used to use that blind period for a change of course and flank speed, and it was a very successful tactic. So, I do believe that the blindness period was modelled.

Was this feature available out of the box or was it delivered with one of the patches ?

It never worked for me, never and the destroyers always homed righ over me one run after another. It took me an eturnaty and most of my battery capacety, till i finaly got away.

Damon

[urseus]

When you get the message "we are being pinged"

does that mean, "they know exactly where we are and are directly pinging us?"

Or they are generally pinging everywhere?


Im very suprised that the depth charge blindness isnt modeled. Ive been doing that alot recently, speeding up during a depth charge run.

Do you have any proof that its not in the game?

[Floater]

I think MacIntyre meant that the turbulence itself would last for about 15 minutes. If I knew how to find the actual passage in the book I'd quote it, but as it is I'd need to scan the whole book to find it.

As for SH2, I think it was modelled in the original game - I don't recall the PM patches mentioning it. You had pretty much total sonic freedom for several minutes, so going flank in a different direction was a useful tactic. CB's mod for DD capability nicely smooths out the original uber-destroyer behaviour, BTW.

[U-104]

I think it is in SH3. Once on a patrol I was under depth charge attack by a DD. As it entered its charge, I hit flank. It came over head and dropped its depth charges. They exploded behind my sub. I went at flank speed for 5 minutes then went ahead slow and it never found me again.

[Floater]

Im very suprised that the depth charge blindness isnt modeled. Ive been doing that alot recently, speeding up during a depth charge run.

Do you have any proof that its not in the game?
Not proof as such, just enough evidence for me to be convinced that it's not modelled. I described that evidence up-thread - I've seen this before, but this is the first time I've deliberately tried to test it, and the approaching DD matched my every move almost instantly despite the DCs exploding close by less than a minute previously.

Let's not mix up the turbulence created with depth charges (which isn't working) with the sonar cone and speed blindness of a nearby attacking DD (which is, AFAICT).

[urseus]

Hang on isnt it the same thing?

They drop their charges over you...meaning you can speed up alot for about 30 seconds maybe while the expolsions are going on.

[Kpt. Lehmann]

Would that be the "Speedy Jameson" Irish whiskey maneuver? :huh:

[yankee-V]

Jameson?! No, that's the "John Full Power" maneuver.

[FAdmiral]

Floater, I'm not sure that being submerged in the middle of a
convoy will mask your sounds either. I got into one on my last
patrol and the 2 escorts seemed to have me detected almost
immediately as they approached. The only thing that saved me was they had to stop & reverse to keep away from the merchants.


JIM

[big_feef]

I've noticed this too, the 'sonic freedom' window after a dc attack to hit flank speed seems to be more than 30 seconds, but less than a minute. Pushing it past 30 seconds tends to get you re-acquired by the enemy sonar 100% of the time.

I usually play at high realism and without the external camera; but when checking this aspect of the game out, I noticed the enemy destroyers following my course turn for turn right after close proximity dc attacks. That should not be possible.

To counter this, I usually do stern shot on my first few targets when attacking a convoy. That way, I should have one or two stationary ships to hide under when the escorts come calling. They'd run around trying to get at me while I slowly go deep until they eventually lose me on their sonar. Unfortunately, this doesn't work that well in stormy weather for obvious reasons.

This short window of 'sonic freedom' after a dc attack isn't that bad early in the war; but as the ASW technology improves around '42-'43 (hedgehogs especially), you have to be very lucky to escape unscathe from a single destroyer dc run... If you're being attacked by more than three, you can just forget it usually.

[Col7777]

While we are on the subject of DC's and being detected etc, how good are the decoys when activated, as yet I haven't tried that?

[CB..]

While we are on the subject of DC's and being detected etc, how good are the decoys when activated, as yet I haven't tried that?

the decoys seem pretty good to me Col!
(i usually place one in an emergency at around 50 metres depth in a crash dive then immediately go to ahead slow and silent running and head deeper after making a slight turn)

BUT here's the problem...

one decoy is a decoy...two is a trail of bread crumbs!!!

[Floater]

I agree with CB - deploying BOLD decoys has saved my boat on several occasions. When you're detected, sling out a single canister, go silent and deep and turn your rear towards the DD. It works quite impressively, as it did in real life.

I'm not sure about the later years, though - I've never played past mid-'44. Experienced ASDIC operators could tell the difference between bubbles and subs, mainly because the bubbles don't move in the same way and the sound of the returns was slightly different.

Frankly, I've always found it amazing that a cloud of bubbles could give anything like the sonic return of a tube of steel, but apparently they did.

[Floater]

I think it is in SH3. Once on a patrol I was under depth charge attack by a DD. As it entered its charge, I hit flank. It came over head and dropped its depth charges. They exploded behind my sub. I went at flank speed for 5 minutes then went ahead slow and it never found me again.
With a lone DD, or with a group of DDs that are not communicating your position, that's understandable. An attacking DD is blind from the moment he speeds up for the depth-charge run - anything over about eight knots and his sonar gear is useless. Then, after he's passed over you, it takes time to (a) slow down again and (b) turn around to get you out of his baffles. A good DD captain could reacquire a target about two minutes after dropping the DCs, but it often took much longer, particularly with the larger DDs.

It's in areas like that that the corvette really came into its own. Being small, they had a tight turn radius, and were also able to accelerate and decelerate much more quickly than a destroyer.

[Shadow9216]

I recently had an encounter that caused me to rethink the whole AI issue...an armed trawler circled my position for several hours of game time despite me doing 1 knot (!), then going all stop and silent running. I was at PD, then 20m, 30m, 50m...finally at 100m he circled for about an hour, then left.

From this same convoy I had deleted :P two T-2s, a C-3, crippled a C-2, and bagged an aux cruiser. I had been aggressively pinged by the Black Swan and Flower that were guarding it, but managed to slip them by using the tactics above.

So how was the trawler able to keep contact? Maybe he was actually trawling, and I was hooked in a net? :-j Otherwise, how was he able to literally circle me- I used the external cam to confirm this, plus my hydrophones- for hours?

[Col7777]

It MAY have been because you stopped and restarted your engines, I believe the sudden noise from this could give you away again, I'm not sure if it is modelled in the sim though.

[U-104]

Maybe he was actually trawling, and I was hooked in a net? :-j a uboat did do that once.

[Shadow9216]

It MAY have been because you stopped and restarted your engines, I believe the sudden noise from this could give you away again, I'm not sure if it is modelled in the sim though


No, he lost me after I stopped the engines- but not until I had been completely dead in the water for about an hour.

So how was he able to perform complete circles around my boat, despite my slow speed, course changes, etc? If I turned to 090, he followed, turning in a perfect circle with me in the center. Turn to 345, same thing, 209, 014, didn't matter. Finally I figured that, even at 1 knot (I manually set the speed), I must be making enough noise to hear- so I went all quiet. He circled, then went away...

[oRGy]

If the sonar blindness from depth charging *is* modelled *but* set to a too low time, then its value is going to be somewhere. Probably in data/Library. I might have a look for it later - starting to almost enjoy hex editing. However I haven't suffered any dd attacks yet (1940)

[big_feef]

However I haven't suffered any dd attacks yet (1940)

1940? You're kidding right? Getting attacked by destroyers before 1942 is like getting slapped by around by your 2 year-old nephew or something. Yeah, it's annoying, but it won't do anything damaging unless you get careless. In all my pre-1942 patrols, I rarely get any damage to my sub from surface vessels unless I do something stupid; only planes tend to get me.

Post 1942 is a completely different story though... One slip and your sub is sleeping at the bottom; permanently.

[the_rydster]

I recently had an encounter that caused me to rethink the whole AI issue...an armed trawler circled my position for several hours of game time despite me doing 1 knot (!), then going all stop and silent running. I was at PD, then 20m, 30m, 50m...finally at 100m he circled for about an hour, then left.

From this same convoy I had deleted :P two T-2s, a C-3, crippled a C-2, and bagged an aux cruiser. I had been aggressively pinged by the Black Swan and Flower that were guarding it, but managed to slip them by using the tactics above.

So how was the trawler able to keep contact? Maybe he was actually trawling, and I was hooked in a net? :-j Otherwise, how was he able to literally circle me- I used the external cam to confirm this, plus my hydrophones- for hours?

Did you enable silent running?

[CB..]

the armed trawlers (pctrawler) do seem to be the most tenacious vessel in the game...staying put and circling you long after the normal DD's have returned to the convoy..this seems to be a regular event ..me thinks the pc trawler has it's own unique AI instructions..it appears to have the same sensors as the DD's etc so there's no other obviuos reason for it being harder to shake.. :hmm:unles as John says it's top speed is low enougth to mean that it never actually loses your contact because it has excellerated above the speed limit for hydrophones and sonar and has such a tight turning circle that it rarely loses you for more than a few seconds..(not long enough for it to give up)

silent running most often loses the DD's most times going to the slightly un-realistic "all stop" state is the only thing that shakes the trawler..

if this was SH2 and not SH3 i'd say :hmm: very interesting...


yup thats it John (Floater :up: ) was right---

the speed set in the game over which the hydrophone stops being effective is 15 knots

[Hydrophone]
Detection time=1 ;[s]
Sensitivity=0.03 ;(0..1)
Height factor=0 ;[m]
Waves factor=0.5 ;[>=0]
Speed factor=15 ;[kt]
Noise factor=1.0 ;[>=0]

(note the speed factor this is the maximum speed at which the hyrophone will work)

the top speed of the armed trawler is

MaxSpeed=12


which means it never reachs a fast enough speed for it's hydrophone sweep to be blanked out ---and it's turning circle is probably the tightest of all the escorts so it can very quickly get you back on the screen..

maybe incresing it's top speed to the same as the corvettes

ie 16 knots

might have the desired result --corvettes being losable without going to all stop (which wouldn't be terribly practicle in real life?)

[Dowly]

Have anyone tried to go to the bottom of the sea and stop your engines while attacked? Do enemies still spot you?

[Happy Times]

Have anyone tried to go to the bottom of the sea and stop your engines while attacked? Do enemies still spot you? I have tried it couple of times in the early years.It worked but i could have just got lucky..

[the_rydster]

It is not possible to hide from ASDIC by sitting on the sea bed since a sub as a different ASDIC profile than the sea bed.

[oRGy]

Interesting find CB: But I believe the realistic setting for them losing you on hydophones is about 12knots.

In an old thread, there was a post by "ridgewayranger" on the topic of sonar - he was an ex-RN sonar operator who was on a DD in '48. He noted:

Over about 12 knots background water noise masked everything else, and there was the risk of damaging the underwater dome, which had to be raised before speed could be increased. Hope this explains some of the real limitations of submarine detection in WW2.
Jim O
Ex.TASI, Royal Navy.

So that setting can be set to 12, which should cure your armed trawler problem. I may actually do this myself for the Improved U-Boat mod.

[Col7777]

There is some reference to this in the Sensors folder too, I don't really understand it that much but I'm sure you guys will throw some light on it.

[CB..]

Interesting find CB: But I believe the realistic setting for them losing you on hydophones is about 12knots.

In an old thread, there was a post by "ridgewayranger" on the topic of sonar - he was an ex-RN sonar operator who was on a DD in '48. He noted:

Over about 12 knots background water noise masked everything else, and there was the risk of damaging the underwater dome, which had to be raised before speed could be increased. Hope this explains some of the real limitations of submarine detection in WW2.
Jim O
Ex.TASI, Royal Navy.

So that setting can be set to 12, which should cure your armed trawler problem. I may actually do this myself for the Improved U-Boat mod.

he he!! what you have to carefull of here is wether the AI will understand that it has to travel slightly slower to retain hydrophone contact or wether it will still behave as if the max speed is 15 which would un-balance the AI ASW tactics..might not ..so worth experimenting with...

you actually might get better results without altering the ships top speeds by experimenting with small increase in the noise level..as the guy said regarding the back ground noise level...im assuming that this is what the noise entry refers to...certainly lowering the entry really sharpens up the DD's hydrophone capabilitys enourmously..

mind you do we know the historically accurate top speed of an armed trawler?---might be worth checking that as well..i'm not a fan of stats for stats sake so i tend to go with what helps in purely gameplay terms..

a bit of both is whats required most times.. :D

for example setting the speed entry lower as you say as long as the AI can cope with it..may actually simulate the effect of the DC's blanketing out the contacts for a longer period of time as the DD's have to speed up to stay safe from the DC explosions..a lower speed will mean that it wil take longer before their phones become use-able again

what is needed is an idea of the slowest minimum speed the slowest dd's use in order to set the speed just above that setting..maybe this would encourage more tactical "creeping" attacks or it might just confuse the AI entirely..as it might behave the same no matter what settings are used..

COL!!! if i know you yull bounce every-one one day with your genius !!don't hide it under a bushel as they say!! :up: :sunny: :-j

[oRGy]

Tried the tweak - setting hydrophone and sonar max speeds to 12knots as in reality - and the result in the u505 mission was predictably enough, nerfed destroyers who couldn't really hear me and at best half heartedly threw a few wabos in my general area, but nothing really terrifying.

(Running RuB btw)

Indeed, it seems as if the game still thought that the acceptable "attack run" speed was 20 knots (for the sonar!), which is interesting. Setting it back to 20 resulted in things working more as normal.

I'm wondering if the value for the AI "max speed at sonar" setting is in there somewhere. If one could set it to an appropriate value, then we wouldn't have nerfed dd's but rather another edge which uboot commanders had in reality.

Hmm...

I should also experiment with the noise factor, and find some research materials. And also stop messing about with this game, but that's another thing entirely.

[Col7777]

I wish I knew more about HEX editing, I opened some CLUT files within SH3 using a HEX editor and there seems to be a lot more info on all this stuff plus more, it might be worth a look there too.

[CB..]

I wish I knew more about HEX editing, I opened some CLUT files within SH3 using a HEX editor and there seems to be a lot more info on all this stuff plus more, it might be worth a look there too.

me too Col--- i was one of the first "non experts" to notice that you could hex edit the SH2 model files to use different external texture files..but that was just a case of altering one letter in a texture name in the model file..i haven't learn't a dang thing more than that since LOL!!!

i have a complete mental block on the stuff...there doesn't seem to be a "begginers guide to hex editng values and what they refer to" available in W-H Smiths either lol!!

all the other tuorials i've seen around the web come in at too advanced a level for me to get my foot on the bottom rung..

[Floater]

corvettes being losable without going to all stop (which wouldn't be terribly practicle in real life?)
Yeah, that's a bugbear of mine, CB. U-boats simply couldn't hover like modern subs without rising or sinking, unlike in SH3 (or SH2 for that matter). Especially at periscope depth, when commanders often had to order fairly high speeds to avoid breaching or losing periscope contact.