How dangerous is to use active sonar?

[kstanb]

I am playing with TMO 2.5 +RSRD with no map update; and it is early in the war (radar is not available), so my question is:

in your experience, how dangerous is to ping a far away convoy? I am talking barely visible ships at more than 8 to 10K yards (stadimeter is useless there)

I have started to use sonar to try to figure out the convoy (or task force) course and range; and then position myself in their path; so for I haven't being spotted, and this approach has been less risky than closing (usually surfaced) to get a better stadimeter read.

thanks in advance

[tomoose]

IIRC there are previous posts asking this question. I don't think the En AI "hear" the ping but I've had a couple of incidents (in my early days) where I pinged and the escorts came a-charging. That could have been a coincidence however. If the En warship AI can't "hear" an active ping then technically it would be "cheating" if you took advantage of a game "deficiency" if you get my meaning. It's a personal choice in how you play the game.

Having said that, realism-wise, I doubt a sub skipper would actively ping if there were enemy warships anywhere around. Someone may correct me but the ONLY time I have used an active-ping is vs a solitary merchant and nothing else. Even then I rarely do it.

[kstanb]

But I read somewhere that in early war, they used sonar intensively; that they would not raise a periscope for fear of spotters, and therefore base their entire solutions on sonar; and as far as I know it is not possible to get a range without active sonar

[TorpX]

Originally Posted by kstanb

But I read somewhere that in early war, they used sonar intensively; that they would not raise a periscope for fear of spotters, and therefore base their entire solutions on sonar; and as far as I know it is not possible to get a range without active sonar

You are correct about range requiring echo-ranging; passive listening is not sufficient. Skippers were trained to make sound approaches before the war, but this tactic was abandoned almost at once. It stemmed from the results of artificial, and highly coreographed exercises where aircraft, knowing when and where to look for the approaching sub, were able to spot it. I think these tactics were predicated on using passive sonar only. AFAIK, there were no enemy ships sunk with these methods. Echo-ranging would give your presense away much faster than using the periscope, generally speaking. The periscope visibility is exagerated, IMO. The danger of having your periscope spotted is mainly confined to 1,000 yds., maybe 2,000 under ideal conditions.

In any case, I don't think echo-ranging works much beyond 5,000 yds or so. Within this distance, you should be able to obtain fair results with the stadimeter. I've never really used echo-ranging in SH 4, mainly because it was seldom used in RL. I'm sure it is possible to sink ships with sonar only (with some luck), but I think it is going about it the hard way.

[Sailor Steve]

Absolutely correct. I posted this on another thread not long ago.
http://www.subsim.com/radioroom/show...81&postcount=7

[Stealhead]

Though to answer the question there is no danger in using the active sonar in game the enemy AI does not "hear" it that was the case in older TMOs I don't think it has changed my guess is that it is hard coded.Not sure with 2.5 though I have never tried it I have tested the no danger of pining in the past and it was true I did that out of curiosity though I never had an interest in trying a sound based attack seems boring to me.

They will 100% detect your radar though if an enemy ship has radar detection capabilities so keep that in mind.

You could also consider attacking on the surface at night this is very possible in TMO and you can get pretty close if you play your cards right.You can spot a TF or convoy during the day and track it until darkness by which point you'll have pretty good idea of its layout and course once you have SJ radar this task becomes much easier and you can use the radar without fear of detection until well into 1943.This depends on what class sub you are skippering with an S-boat getting into a good spot can be fairly hard thanks to the low speed in any other class it will be much easier because you can usually exceed the speed of the TF or convoy in most cases and have enough speed to change if need be.Of course all well laid plans can easily be dashed if your cat decides to jump onto your keyboard at the precise moment for the glory of the Japanese Empire.

[gi_dan2987]

I've been reading these posts and feel the urge to toss in my two cents. Real WW2 skippers would have to know the exact position of their submarine at all times on their maps in order to make accurate use of the famous 4 bearing method. Unlike in SH4, real skippers did not have the luxury of having a little submarine icon move around on their map like it does in game. So that's why sound only attacks were rare and inefficient. Sound contacts could give you an idea, but much plotting would have to be accomplished prior to the attack in order for it to properly work.

In regards to the comment about echo-ranging; I use RFB 2.0 with SH4 1.5. I will track a convoy on my surface radar until I have a good idea what their course and speed is. I then set up, wait until they're within visual distance, and begin range/bearing readings with the periscope. I make any necessary adjustment to the TDC according to the information gathered from the plots, and prepare my torps for firing.

Now here comes the part regarding preference of attack. I find that pinging for range/bearing, adjusting AOB to match course, and firing is much more fast and accurate than rifling through an ID book with my scope up in the air. Especially at night when it's hard to ID ships and see masts and funnels. I suppose real skippers would do whatever it took to gain accurate solutions. If it's dark and foggy/rainy/etc, you aren't going to be using your scope to much effect now are you?

Now here comes some questions I have for any and all to answer:

1. Regarding active sonar, can all ships (including merchants) detect when they're being pinged and begin evasive maneuver/attack?

2. Comparing apples to oranges, what is more accurate, Using stadimeter and periscope to obtain final range/bearing or using active sonar? Which one is less conspicuous? What are the advantages/disadvantages to both?

3. Concerning radar (surface and air search), from how far can the enemy detect your signals assuming they can detect them?

The reason I ask question 3 mainly is because I just completed a mission where I seemed to attract Jap convoys and task forces like flies. I fired all 24 torpedoes and racked up 30,000 tons in a hurry, but they never stopped coming. I had to run silent at test depth for most of my return trip to brisbane in my Gato class. As soon as I would surface and kick on the radar, I started attracting flies. If anyone can help me out here that would be great. Cheers!

[groomsie]

Originally Posted by kstanb

But I read somewhere that in early war, they used sonar intensively; that they would not raise a periscope for fear of spotters, and therefore base their entire solutions on sonar; and as far as I know it is not possible to get a range without active sonar

Actually, this is not correct. It isn't easy to develop the range via passive sonar, but it can be done. I used this while I was in the Navy for tracking subs with a towed array, but it was developed after WW II by Lt Ekelund (story here). If you have a smart phone you can use the Ekelund range application...

Now, it is true that this was not possible in WW II without active sonar...

[groomsie]

Actually as I recall we just referred to it as TMA (target motion analysis), and we also used the technique to come up with estimated range, estimated course, and estimated speed of the target using both passive sonar (for surface and subsurface) and detection of radar emissions (for surfaced targets).

[Daniel Prates]

I think that TMA is only possible when you can correctly estimate the target's speed. Then you compare multiple bearings over a period of time, and 'fit' both data (bearings and speed) into one coherent result. If you only have the bearings, his range (and relative course too) are impossible to estimate.

So the thing is to estimate speed via some reliable source. The way I see it, the mode of choice in the last decades is TPK (turns per knot), a thing you only can use if at the same time you can also classify the target, all of that presuming you know the TPK ratio for it- a not so easy thing to do with 1940s sonar gear and intel.

[groomsie]

You would be correct for single leg TMA. To get a single solution for speed you would do multi-leg TMA.

The Eckelund method does not require any estimate of target speed, it provides range only.

I am not sure when the specific techniques I previously was familiar with were developed, but I agree they would be tough in WW II era subs.

[merc4ulfate]

I have only used active sonar to lure destroyers away from convoys. If I ping them from a 90 degree bearing then dive and go ahead flank they are more apt to center in on my last position where the ping came from while I angle in towards the body of the convoy. Imagine a T where the bottom of the letter is my position the far right point of the top cross bar is the merchants and once I pined them I headed for the top left point of the cross bar to intercept.

It really work well once in shallow water I'd say 100 feet with a rough surface. The destroyers stay in the area I pinged from while I intercepted and fired torpedoes at the merchants. By the time they turned and came back I had sank three ships and was heading away from them. They depth charged the area they thought I was in but I was a good 2000 yards away and they never approached me.

[Rockin Robbins]

Originally Posted by merc4ulfate

I have only used active sonar to lure destroyers away from convoys. If I ping them from a 90 degree bearing then dive and go ahead flank they are more apt to center in on my last position where the ping came from while I angle in towards the body of the convoy. Imagine a T where the bottom of the letter is my position the far right point of the top cross bar is the merchants and once I pined them I headed for the top left point of the cross bar to intercept.

It really work well once in shallow water I'd say 100 feet with a rough surface. The destroyers stay in the area I pinged from while I intercepted and fired torpedoes at the merchants. By the time they turned and came back I had sank three ships and was heading away from them. They depth charged the area they thought I was in but I was a good 2000 yards away and they never approached me.

Now THAT is a great tactic! I love it!

[twm47099]

I've been trying to learn how to use different attack methods including radar only and sonar only (active and passive and passive only).

I have a practice mission (one merchant ship, dark night) that I use. I've been pretty successful using radar only (with the OTC mod) and find that the radar range agrees closely to the chart plot ranges (with the radar and sonar only attacks, I do check once I've fired the torpedoes).

Today I tried the 4 bearing passive sonar method to get course, bearing, and target speed (3 bearings with sub stationary + one more after moving to get range.) I had the sub at 70 ft so I wouldn't get any cues besides the sonar trace which I used for the bearing measurements. I did check range with active sonar once I had a plot running, but the range was more than double the predicted (and later verified range.) So far I have not had any success with using active sonar to predict range (always over estimates.)

As the passive only attack evolved, I chickened out and decided that since the range was the most questionable thing I would use a constant bearing attack (once set up I did a second 3-bearing check on target course, but was running out of time and couldn't make the run to get a check on range)

I choose a 60 degree attack, and loaded the aim bearing, AOB, and speed into the TDC. I used the attack map which showed the sonar bearing and when the sonar trace crossed the 353 degree bearing (my aim bearing) I fired one torpedo. Once I launched I rose to P depth and raised the scope so that the ship would show up on the attack map. I had calculated the ship would be at 1600 yrds when it crossed my zero bearing, but it actually measured out to 1950 yrds. The course (and actual AOB) were accurate. The torpedo hit.

Biggest issue is that it took me a long time to collect the bearings (I used 5 minutes between bearings), and a very long time to do the graphic construction (zoom in to the chart to locate the points accurately, and zoom out to extend the lines.) Thank goodness for "pause game". I bet the WWII submariners really appreciated their pause buttons And there was not enough time to recheck range.

I am surprised that my active sonar ranges are so far off.

Tom

[kstanb]

thanks a lot for your answers;

I think I will ping an escort at close range to see what happen