Depth-charge turbulence
 

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?

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.

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

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...

Re: Depth-charge turbulence
 

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

I tell ya.

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 :)

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

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

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.

@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.

Cool!

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

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.

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.

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

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 ?

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

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?

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.

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.