Static Search Vs. Dynamic Search

[TorpX]

There was some discussion in the thread TMO fuel usage at 0 knots, and this lead to the question of which is better, sitting still or cruising around to look for targets. This got me to thinking about it a little more deeply, so I did some math....

To illustrate the idea, lets say you are a new SH 4 Captain, who has just been put in command of a shiney new Gato class fleet boat. You will be shortly sailing from Midway, to a patrol area in the vicinity of the Luzon Strait. Since this is your first war patrol, you are undecided about whether to use a 'static search' or 'dynamic search' method. Fortuantely, your experienced, dedicated, and hard-working XO, has prepared a short report to help you. ;)

Mathematical considerations:

For simplicity sake, we will only consider merchant shipping, and will assume that it is all following a single axis (say north to south and south to north), we will further assume that our cruising in the patrol area is perpendicular to this shipping lane. This provides an optimum chance to obtain a contact if we are using the 'dynamic search'. It is also assumed that ships are randomly distributed in the region we are patroling (i.e. not clustered in any particular line or region).

Once the geometry is done, we have:

Pr = 2 * Rd / sin a
......where a = arctan (Vt / Vu)

Pr is relative probability or finding contact
Rd is detection radius of your boat
Vt is speed of target
Vu is speed of sub

Note that if Vu is 0, a is undefined, but we know from the geometry that a = 90 in this case.

Here is a tabulation to show how the probability of obtaining a contact, in a given time period, is enhanced by the sub cruising at speed (the targets are assumed to all be traveling at 9 kts in this problem):

Vu..................... a ....................Pr
0......................90....................1
5......................60.9.................1.14
10...................42.0.................1.49
15...................31.0.................1.94

The relative probabilities are indexed so the lowest figure is 1, this being the 'static search' value. I call the margin of the higher values the 'search bonus'. So we have a modest 'search bonus' for slow cruise at 5 kts., a slightly higher bonus for 10 kts., and a still larger one for 15 kts. This would seem to settle the issue, but we're not done yet. Let's see how our fuel budget looks for our patrol. For simplicity, we will compare a static search patrol to a dynamic search where we cruise at 10 kts. This allows us to use the quoted endurance figures without having to guess how fuel consumption changes at a higher or lower speed.

STATIC SEARCH
total endurance 11,000 nm @ 10 kts

round trip to patrol area...................7,000 (29 days)
safety/weather allowance................1,000
tactical pursuit/evasion....................1,000
remainder available for search........2,000

31 days using 20/day..........................620
extra* .................................................1 ,380
This allows 31 days on station. I will assume we terminate our patrol at this point. So we could use this to move 20 nm each day a have extra* left over. I'll come back to this later.

DYNAMIC SEARCH
The first four lines are the same, except:

8. 33 days cruising at 10 kts............2,000
So we have only 8 days to search here. When we multiply the relative probabilities of finding a contact by the number of days on station, we get:

static search.............31 * 1.00 = 31
dynamic search....8.33 * 1.49 = 12.4

However, there are also practical considerations:

1. If venturing into shallow water is contemplated, it would be desirable to move in at night, and then leave before daylight, fuel considerations notwithstanding.

2. If the patrol area has prodigous shipping, fuel may not really be a limiting factor. In this case, we have more flexability, as far as fuel is concerned.

3. The 'static search' plan would allow for a limited redeployment, if we should find ourselves in a shipping desert, without cutting short the patrol. (Remember the extra fuel.) The 'dynamic search' plan does not.

4. If we find ourselves in an area where there are no targets, the 'search bonus' does not help us. On the contrary ,cruising around faster will merely exhaust our fuel faster. You can't detect targets that are not there.



Any thoughts?

[gi_dan2987]

I totally see the point you are trying to make. I personally think that if the target is within feasible sailing distance, and you're not nearing the point of no return on your fuel level, then making a solid dash for attack position would be well worth the extra go juice.

I personally find that galavanting around at optimal cruise speed on the surface on a search course is the best way to increase odds at running into something. While surfaced and cruising around, you're covering way more square area in a shorter amount of time than putsing around submerged with the hydrophones. Granted your watch crew may have a detection radius much smaller than your hydrophones, but the larger area you can cover on the surface more than makes up for lack of spotting radius.

When you finally equip radar, surfaced patrol is undoubtedly the best method, as radar will out range both eyeballs and hydrophone alike. Then of course there's your contact reports to go off of. All in all it's a patrol just to see what's out there, and sometimes there is nothing. Historically many subs went out on patrol for months only to see miles of empty ocean.

I suppose this is why they call it hunting and not killing right? heh :smug:
Since we're on this subject of patrols and what not, would you have any suggestions as to plotting accurate speed readings? The stadimeter stopwatch icon seems to give me poor estimates, and the measuring tools have a built-in error margin that increases with distance. There's gotta be a way..... :hmmm:

[magic452]

I suppose this is why they call it hunting and not killing right? heh :smug:
Since we're on this subject of patrols and what not, would you have any suggestions as to plotting accurate speed readings? The stadimeter stopwatch icon seems to give me poor estimates, and the measuring tools have a built-in error margin that increases with distance. There's gotta be a way..... :hmmm:


Edit I just read in another post that you don't want to use map contacts so the following is not for you. Maybe will help someone else. :06: Map contacts is a bit too easy and off I really didn't enjoy, so I use contacts on.

Playing with map contacts on just have your sonar man track closest contact and then mark your X at the end of the bearing line.
For a convoy you'll have to pick a target and follow it yourself.
That range is pretty accurate and you can plot course and get speed by the three minute rule. I do 3, 6 and 9 minutes and get a very accurate speed and course. The three minute rule; for radar or sonar contacts wait till the target updates (20 seconds for sonar, 30 seconds for radar).
When it updates place an X on the target or the end of the sonar line.
Start the stopwatch. Wait 3 minutes (3.25 minutes for metric) and mark another X when the target is updated. The distance between the Xs in yards divided by 100 will equal the target speed. 500 yds = 5 knots, 1000 yds = 10 knots. Do this three times and you'll have an very good target course and speed.

Take the ruler and turn on tool helper and you get a compass rose, place the center of the rose on the target course line and read the number closest to the target. That is the target heading in degrees. remember this number. Go to the peri screen and first turn on the PK. Next go to the data input dials and input speed and sent to PK. Third go to the AoB dial and turn the dial to the side of the target you will shoot at, Starboard or Port. Turn the dial a few degrees and send to PK and when you do you'll see the top dial on the left side move and the bow of the target will point to the ring of numbers on the outside of the dial. Those numbers are the target course in degrees (4=40°, 9=90°,etc.) Just turn the AoB dial till the bow of the target ship points to the course you measured on the map. Once the target lines up with that course send to PK. You now have a very good AoB and the PK will keep this for you as long as the target holds course and speed.

You now have two thirds of your firing solution and you haven't even seen the target yet.

A couple of good steadimeter readings to get range/bearing and you're all set. Check the firing solution on the attack map and make any last minute adjustments.

This is called killing.

Magic

[magic452]

I only use a dynamic search even from Pearl and refueling at Midway. I have seldom had any real problem with fuel limiting my patrols. I run out of fish long before fuel becomes a concern. Once I hit very heavy weather all the way back to Midway and just did make it. I usually port in Fremantal or Brisbane and fuel is not any concern at all.

With sonar only I set up a patrol pattern with each leg about 10 nautical miles and do a manual sonar sweep at the end of each leg, I'll wrap the search around the end of each leg to cover my 6. That's one sweep every hour at 10 knots. You cover the most area and find the most targets.

Once you have radar sitting still makes no sense at all.

I don't think I've ever had any patrol last more than 35 or 40 days.

Magic

[TorpX]

I totally see the point you are trying to make. I personally think that if the target is within feasible sailing distance, and you're not nearing the point of no return on your fuel level, then making a solid dash for attack position would be well worth the extra go juice.

I personally find that galavanting around at optimal cruise speed on the surface on a search course is the best way to increase odds at running into something. While surfaced and cruising around, you're covering way more square area in a shorter amount of time than putsing around submerged with the hydrophones. Granted your watch crew may have a detection radius much smaller than your hydrophones, but the larger area you can cover on the surface more than makes up for lack of spotting radius.



Perhaps this wasn't clear from my OP, but I consider there is a BIG difference between using fuel to pursue a known contact, and using fuel to cruise around aimlessly. I think most, if not all, skippers would have used almost any amount of fuel to attack a definate target. Also, I should clearify what I mean by a 'static search'. In my example, I allowed for 20 nm movement each night. ( O'Kane mentions this as a safeguard, in case they had been spotted by an aircraft and the enemy was routing ships around their position. Maybe I'm the only one who reads O'Kane. :))



Anyway, to return to my example, searching at 5 knots only increases your chances by 14%. Searching at 10 kts. gives a 49% greater chance per day. This sounds good but.... this is at the cost of reducing your time on station by a substantial margin; hence your gains are illusory.

One thing I didn't include in the OP, because I hadn't thought of it at the time. The figures if calculated are based on a searching boat moving at a right angle to the shipping lane. If the searching boat is to stay inside the lane, it must periodically reverse course and backtrack. This would have the effect of reducing somewhat the 'search bonus'. (The boat would be searching water just recently travelled through.) How much, would depend on how often it would turn around.


While surfaced and cruising around, you're covering way more square area in a shorter amount of time than putsing around submerged with the hydrophones

It is not the square area, but the radius that is important. If you can see 5 nm and you detect X % of ships transiting the area, a 10 nm visibility will allow you to detect 2X %,(not 4X %). This may seem counter-intuitive, but if you diagram it, you will see it is true.



If you want a rule-of-thumb, I would say limit your fuel use in such a way that you would be able to complete your patrol schedule. That is, for a fleetboat, be able to remain at sea for at least 60 days. I'll admit, it is more "fun" to be cruising around "doing something" than sitting still, but this is not the same as saying it is a more successful tactic.

I was thinking it would be interesting to try to pin down the math more, so different search patterns could be analyzed according to the assumptions used, but as you are the only one to post a reply, I'm guessing there is limited interest in this topic. :-? Anyway, thanks for the response.

[Armistead]

The formula probably has more bearing historically than it does in game. Course he may have readjusted fuel for 2.5, I'm still playing 2.2 where fuel really isn't an issue.

Even before that fuel has never been an issue, stay in shipping lanes and the traffic will come.

[magic452]

Just a few thoughts.

If I remember right you wouldn't get a mission to Luzon from Pearl via Midway. You would go to Japanese home waters that are closer so you have more fuel for patrolling. This would hold for both methods but with the static patrol the extra fuel would do you much good because you are already staying out 60 days.

I can only think of a single time I've spent anything near 1000 nm in pursuit and evasion. I chased a fast TF in heavy weather at flank speed for something like 200 nm. Even at that I RTB for torpedoes not fuel, I had one left. I was out of Brisbane so fuel wasn't a real factor.

Safety/weather allowance of 1000 nm. seems rather excessive.

So in my experience I have a lot more fuel than you are allocating for patrolling. I can't think of a single time I patrolled for only 8 days, it just hasn't happened.

31 ships in 31 days of paroling. Nice if you can sink 31 ships with only 24 torpedoes. In my experience two fish for every target and some times three.
dynamic search = 12.4, two torpedoes per ship = 24+ torpedoes.
A static search will net you 12 ships at best in 12 days or more patrolling and you RTB for lack of fish and fuel is no factor. I've gone many a day without seeing anything at 10 knots and that is covering 220 nm. more than a static search would and that's at 0.49% higher rate.

The idea is to sink enemy shipping not stay on patrol as long as possible.

The only time a static search would be of any real value is if you are assigned to patrol the entrance of a major port, a choke point or a mission to the Sea of Japan and even at that I think a dynamic search would be more productive. These areas are patrolled by aricraft and you can get down much faster at 10 knots than you can at zero. What O'Kane did or didn't do has little relevance to playing this game. Things just don't work like they did in real life.

Where do you get that PR figure? 1.0 verses 1.49 at 10 knots.

I don't patrol perpendicular to a shipping lane but rather zig zag along it's length.

#3 With a dynamic search you will leave that shipping desert just by the fact you are moving and patrolling the biggest possible area.
With a static search you leave that desert 20nm. a day or the the whole fuel thing falls apart. There are lots of shipping deserts out there and you go where you are sent. If you're playing by the book you do your patrol and call in for another mission, can get sent to many shipping deserts this way.

Anyway for my torpedoes I'll patrol at 10 knots and take my chances.

Magic

[Stealhead]

I fully agree with Magic your duty is destroy enemy shipping therefore one should use the tools at hand to maximum effect by staying in one spot your are adding the Japanese because now they just need to have the poor luck to come to you by being mobile they now must deal with the bad luck of being within 200 miles of you.I think like a tiger each tiger has a large bit of land that is his and he roams it constantly.

Considering that all of the most successful US Navy submarine captains all firmly believed in actively patrolling or "dynamically" searching it seems to me that it is the best method.Why sit in one spot and wait when you are very likely missing something 30 miles away that is not headed in your direction.I have never had fuel consumption issues myself with various versions of the game even if having to leave a dry area.I would say in most cases performing an active search in the typical "patrol this area for X hours" and covering a 100-120 miles radius I very rarely wind up not finding a ship or ships often I will find a convoy attack it and move on and wind up finding and hitting another convoy 40 or 50 miles and few hours searching later.Seems to me by sitting in one spot you are greatly lowering the odds of finding a ship unless you knew for certain that something was going to pass your position which in most SH4 missions you do not.I find a known lane and go hunting.If you ever read "Thunder Below" by Gene Fluckey you will be firmly convinced how much more effective it is to actively search but all the successful skipper where like minded they would have felt that being static and conserving fuel would be counter productive to searching the greatest area and therefore increasing your of finding ships which of course is the primary mission to seek out and destroy enemy shipping.

[TorpX]

The formula probably has more bearing historically than it does in game. Course he may have readjusted fuel for 2.5, I'm still playing 2.2 where fuel really isn't an issue.

Even before that fuel has never been an issue, stay in shipping lanes and the traffic will come.

I did intend this more for historical interest than as being essential for SH. People seem to either have a hard time understanding the math or just don't want to change their prefered game style. Oh well.

[Armistead]

I did intend this more for historical interest than as being essential for SH. People seem to either have a hard time understanding the math or just don't want to change their prefered game style. Oh well.


Yea, I get it, problem is odds math seldom worked in history or in real game, but interesting concept.

I sort of static and dynamic, depends where I'm hunting. If I'm in Formosa I know groups going north or south cant get past me, so I can sit there. The same with the shipping lane off the west coast of Borneo, you can sit 30 nms of Brunei and catch the large RSRD or TMO for that matter convoys coming either way. Simply, if you know the right places, you can sit and the traffic will come to you. That's the problem with predetermined traffic, easy to deal with once you know it.

Seldom did subs static search historically, they were basically always moving, moreso when they started acting like surface raiders. I think in Wahoo, the first patrol with an old Captain Wahoo spent over 500 dived, when Morton took over, it was 60 hours the first patrol......that's balls. He made subs moving surface raiders.

[TorpX]

Just a few thoughts.

If I remember right you wouldn't get a mission to Luzon from Pearl via Midway. You would go to Japanese home waters that are closer so you have more fuel for patrolling. This would hold for both methods but with the static patrol the extra fuel would do you much good because you are already staying out 60 days.

The reason for conserving fuel is so you have it when you need it. If you get an ultra message or decide to move 300 nm to a different area, it is nice to have the fuel to do it.

I can only think of a single time I've spent anything near 1000 nm in pursuit and evasion. I chased a fast TF in heavy weather at flank speed for something like 200 nm. Even at that I RTB for torpedoes not fuel, I had one left. I was out of Brisbane so fuel wasn't a real factor.

The 1,000 nm is not to be taken at face value. 1,000 endurance at 10 kts is likely to be more like 250 at 20 kts. I tried to stick to the 10 kt endurance figures, since those are the figures quoted. If anyone knows the actual fuel consuption at 15 or 20 kts, please help me out.

Safety/weather allowance of 1000 nm. seems rather excessive.

See above.

So in my experience I have a lot more fuel than you are allocating for patrolling. I can't think of a single time I patrolled for only 8 days, it just hasn't happened.

First, I used a fairly distant patrol area for the example. Second, mod and game issues change what the in-game fuel consuption will be. I just used the quoted 11,000 nm @ 10 kts. figure.

31 ships in 31 days of paroling. Nice if you can sink 31 ships with only 24 torpedoes. In my experience two fish for every target and some times three.

Don't get hung up on the exact figures. These are relative numbers of contacts. In a low traffic area, the "31" contacts could be 3 or 4. The point is that if one method gives 30 relative contacts and the other gives 15, this says you can expect twice as many. The actual number would depend on the volume of shipping and your luck.

dynamic search = 12.4, two torpedoes per ship = 24+ torpedoes.
A static search will net you 12 ships at best in 12 days or more patrolling and you RTB for lack of fish and fuel is no factor. I've gone many a day without seeing anything at 10 knots and that is covering 220 nm. more than a static search would and that's at 0.49% higher rate.

As I said above, these are the relative probabilities of a contact, not the actual number of ships. This is impossible to calculate with very specific data for a particular area.

The idea is to sink enemy shipping not stay on patrol as long as possible.

A short patrol runs the risk of having few (or no) contacts. It's possible to run around like a speedboat and find a good number of contacts if there is a high volume of traffic to find. It's just as possible to burn up your fuel and be forced to RTB emptyhanded. There were war patrols where boats came back after 60 days with all their torpedos. Since you have no good way of knowing how many or when you will get contacts, it makes sense to plan for a long patrol from the start.

The only time a static search would be of any real value is if you are assigned to patrol the entrance of a major port, a choke point or a mission to the Sea of Japan and even at that I think a dynamic search would be more productive. These areas are patrolled by aricraft and you can get down much faster at 10 knots than you can at zero. What O'Kane did or didn't do has little relevance to playing this game. Things just don't work like they did in real life.

You may not like O'Kane. I started this thread for those who are interested in the RL techniques/math of patroling. I agree SH 4 is not too much like the actual war. IMO, it is rather too easy to come up with targets in the game. It depends a lot on your style of play.

Where do you get that PR figure? 1.0 verses 1.49 at 10 knots.

I gave the formula used in the OP. I have no easy way to post a diagram ATM.

I don't patrol perpendicular to a shipping lane but rather zig zag along it's length.

Going back and forth perpendicular to the shipping lane is the optimum method. This is easily visualized if you imagine going parallel to the shipping lane. You would not make contact with any ships that were not going make contact anyway. You would only hasten the contact from one direction or delay them from the opposite direction. Zigging has some advantage if you just "passing through" an area, but I don't see much advantage if you have reached the area you want to patrol.

#3 With a dynamic search you will leave that shipping desert just by the fact you are moving and patrolling the biggest possible area.
With a static search you leave that desert 20nm. a day or the the whole fuel thing falls apart. There are lots of shipping deserts out there and you go where you are sent. If you're playing by the book you do your patrol and call in for another mission, can get sent to many shipping deserts this way.

Again, you are not understanding the concepts here. I don't want to get into the whole mission/patrol area thing. I know some people ignore mission orders altogether, some are diligent in following them. I doubt many will spend a whole patrol in an unproductive area. If you use a static search technique, you can search an area for a week or two, and if you have not found anything you have plenty of fuel for a redeployment ( within reason). If you are using a dynamic search, and you spend a week or two and come up empty, you may not have enough fuel to do much about it.

Anyway for my torpedoes I'll patrol at 10 knots and take my chances.

Magic
Anyone is free to play as they please. I should like to reiterate this concept is not really mine originally. O'Kane mentions this in his book. I don't remember the exact words but the jist of it is that racing around did not provide much advantage in searching for contacts. He said this could be shown mathematically. I just did the math.

Many times new people have made posts asking why they can't find targets, or why they don't have enough fuel. Often, the response is to go here or there, because there is a lot of traffic over there in that time period, or a battle will happen on such and such date. RL captains did not have this advantage. They had to rely on sound technique and perserverence. I have attempted to show how they were able to do this.

[magic452]

I think we are talking about two different things here and I do see your point.

You're wanting to enhance the realism of the game with real world tactics.
This is fine

I'm trying to maximize what the game gives us to play with. I'm not a real stickler for realism I guess.

I don't have anything but respect for O'Kane but I play more like Morton.
I'm no WWII navel historian by any means but O'Kane and Morton and the like were no doubt given the best assignments. The 60 day no contact patrols were given to captains of lesser ability. You send your best to where the action is most likely to be. A 60 day no contact patrol may be realistic but not a whole heck of a lot of fun to play IMO.

The point I was so poorly trying to make is that, in the game, fuel is seldom a real concern so a dynamic patrol works well. So I'll take the higher rate of return and RTB as soon as possible and get back out as soon as possible. Torpedoes will be the determining factor not fuel.
Again in areas where a static patrol would work good are also where the flying thingies are and you can dive faster at 10 knots than zero.

I follow mission orders and call in and go the the next mission, don't freelance much. In game mission orders are far different than real ones but I'm not racing around with no plan, I use a tried and proven patrol method. The method depends on several factors, time, place, type of boat, etc.

I've tried perpendicular patrolling, not had much success with it but you make a good case so I'll give it another go in the right places.

As far as Ultra reports go I've only had two that were anyway near enough to take any action. The TF in my last post was one and the other was the Big Y near Truk. Long chases for both and still no fuel issues.

Your 10 knot speed is just fine with me as that is the most fuel efficient game wise and I never exceed that unless I'm in hot pursuit.

I was taking your figures to seriously and to be truthful I misread your formula as being absolute rather than relative. I'm not my sharpest at 1 AM, come to think of it, not all that sharp at 1 PM either.
Heck it's 1 AM again. :damn:
Good debate sir :salute:

Good luck and good hunting.

Magic

[gi_dan2987]

I would like to interject on all of these thought-provoking topics. First off, what is the name of this book by Mr. O'Kane?

Every skipper has different methods that could work given the circumstances. I believe that every situation is different and requires the ability to adapt. That being said, sometimes surface patrol courses are more effective than submerged static/dynamic sonar sweeps and vice-versa.

Captain Morton of the USS Wahoo took a sub that was once commanded by a cautious man who lacked proper incentive and aggression, and turned it into a tonnage logging, effective war machine. Mr. Morton spent a lot of time actively patrolling on the surface. Granted his crew paid the ultimate price for their bravery and aggression, but they also are listed in the records as one of the most successful submarines of the war.

[Stealhead]

O'Kane wrote two books one was about the Wahoo it is called "Wahoo: The Patrols of America's Most Famous World War II Submarine" O'Kane spent much time on this boat but obviously was not aboard when she was lost but he does his best to estimate her last patrol and hed have the best idea seeing as he was the XO for Morton.

The other book is called "Clear the Bridge" it is about the USS Tang which was O'Kanes boat she was lost to a circle runner but O'Kane a few others survived.Both books go into great detail the methods used by O'Kane and Morton while on patrol and they stayed in one place rarely.

"Thunder Below" is another excellent book written by a submarine commander Gene Fulckey who received a Medal of Honor for his exploits his book is very detailed as well.Fluckey who clearly from reading the book was a very good officer and cared greatly for his men and defends both O'Kane and Morton who had bad reputations with some war is war people die even when you make the correct choices and neither man made any obviously huge errors in judgment it was just a better day for the Japanese that day.

Personally I after reading these books largely used the same tactics and I had a lot of fun doing so therefore ever since then that is how I play.It seems to me that most of the successful boats generally searched actively most of the time but if the situation warranted they might stay immobile that can be very useful in some situations like if you are near a cost line and seeking a ship hugging the coast staying stationary is wise because you know generally where the vessel is going to be this tactic is also useful in several locations in Japanese home waters.

[TorpX]

I'm still not entirely sure everyone understands what I am trying to say. When I use the term 'static search', I don't mean that one spends weeks firmly anchored to the same spot. More like moving 20 or so miles each night, so that you work the patrol area bit by bit. You could, if you wanted, cover the same distance in a single night, but if it is a light traffic area, the odds are you will not come up with anything in a single day, no matter how far you go. Realistically, I think there were many areas where there would be only one or two potential contacts moving through the vicinity each week. Also, I am assuming that there is quite a bit of movement in attack and evasion, whichever search method you use. Perhaps the term 'static search' is not really the most appropriate term. I think we all agree it is preferable to remain surfaced as much as possible. I more or less assumed this in my example, as submerging reduces your detection radius.


I had not thought of it before, but the Kriegsmarine used a variation of this idea. When they wanted to attack a major convoy on the Atlantic route, they had a idea where it would pass, but of course had no way of knowing exactly. Their solution was simple, but effective; arrange a line of U-boats accross the expected path, 15 or so nm apart, and wait for one of them to make contact and report. As long as the boats (pickets) remained fuctional and on station, they were sure to locate the convoy. Donitz called these 'rake operations'. These sorts of tactics may strike many as too "passive", but the passive phase comes to an abrupt end as soon as contact is made.


Here is a slightly different example to further illustrate the concept:

Suppose you are astride a N-S sealane and want to "search" it. I will assume, as before, freighters traveling 9 kts. and a 10 nm detection radius. (This is good for SH 4, since nothing is rendered beyond 10 nm anyway.) If you sit still you will detect 100% of ships in a 20 nm "slice" (10 nm East and 10 West). If you want to move E-W across the sealane (in effect yo-yoing back and forth), how far can you go East or West, without letting ships "slip through"? If you are cruising at 10 kts., you can go 11.1 nm on either side, and still make sure nothing gets by in the center. Why do I say 11.1 nm? Because in the time it takes you to go 11.1 nm East and 11.1 nm West (back where you started), an enemy ship could move through the 20 nm deep band you are searching. Going any farther would allow some ships to slip past. Following this plan, you will detect 100% of ships within this 22.2 nm zone, and some of the ships within a 10 nm 'fringe' zone on either side. If you wanted to cruise at 15 kts., the figures would be 33.3 nm with a 10 nm 'fringe'.


The point I'm trying to make here is not that a dynamic search is no good, but only that it doesn't necessarily improve your chances as much as it would appear.

[Armistead]

I get the concept and Wahoo certainly did it to a degree. I am in fact reading "Wahoo" again for probably the 10th time. One thing our game lacks is historical realism that would make submerged static hunting viable since we play against AI.

Near Japan Morton did more submerged static hunting, but would place himself in shipping lanes and choke points. When he sunk ships, he usually quickly moved to another location 50-100nm's away and attacked again hoping the enemy would think two subs were in the area and split their ASW effort. Near Japan if you were spotted it usually prompted a ASW response, so one stayed dived more during the day. Many of the island chains also had land radar which would pick you up.

The other factor missing in game is ocean currents.

I added a lot of China coast traffic in 44 and 45 that basically hugs the coast and travels between the small islands and reefs, in and out of ports, not to mention many patrol boats, fishermen, minefields, shoreguns, coastal lights, air patrols, etc.. In such shallow water it's a dangerous game. I go in at night and attack and slip back to the deeper edge during the day and static hunt where I can still pick them up on sonar. It's fun playing, but hard and mistakes or risk can easily get you killed.

[magic452]

Here is a slightly different example to further illustrate the concept:

Suppose you are astride a N-S sealane and want to "search" it. I will assume, as before, freighters traveling 9 kts. and a 10 nm detection radius. (This is good for SH 4, since nothing is rendered beyond 10 nm anyway.) If you sit still you will detect 100% of ships in a 20 nm "slice" (10 nm East and 10 West). If you want to move E-W across the sealane (in effect yo-yoing back and forth), how far can you go East or West, without letting ships "slip through"? If you are cruising at 10 kts., you can go 11.1 nm on either side, and still make sure nothing gets by in the center. Why do I say 11.1 nm? Because in the time it takes you to go 11.1 nm East and 11.1 nm West (back where you started), an enemy ship could move through the 20 nm deep band you are searching. Going any farther would allow some ships to slip past. Following this plan, you will detect 100% of ships within this 22.2 nm zone, and some of the ships within a 10 nm 'fringe' zone on either side. If you wanted to cruise at 15 kts., the figures would be 33.3 nm with a 10 nm 'fringe'.

A couple of points here.

First a sea lane is not a narrow straight line even in the heavily traveled choke points. Markassar Strait is about 50 nm. wide. Luzon three times that.
Shipping lanes are no doubt about the same. You can sit in the center and still leave more than enough room for convoys to sail right by. Why give up the higher percentage for contacts just to save some fuel that is for the most part not an issue.

Second ships and convoys don't run straight courses they zig zag and can very easily sail right past you. Again a dynamic search will increase your chances of making contact and I would think the increase would be greater than what your figures suggest. The zig zags put them in your contact zone longer than a straight course would. The course changes reduce their overall progress on their base course. I do your yo-yo across the lane almost exactly as you describe but I'm also moving North or South. I described this in my second post.
Again your giving away contacts to save fuel you most probably won't need.

Third Radar. 20 nm. range Your search area doubles and enabling you to cover most of area of a choke point if you're moving.

If I'm in a dead area I'm going to patrol in a way that searches the greatest area in the shortest amount of time. Your not going to find much no matter which method you use.
Your mission is to interdict shipping not stay on station for 60 days. They have other boats to replace you in that area.

I'm wanting to RTB knowing I gave myself the best opportunity to have success.

And when I get there I'm going to say "I one of the top guns and don't send me to the Marshals again." I'm sure they will listen. :D

But I do see what you are saying and your points are well taken, I can see several places that a static search might be the best tactic especially early in the war where fuel is a little bit bigger concern. Armistead has pointed out a couple as well.

Magic

[TorpX]

I get the concept and Wahoo certainly did it to a degree. I am in fact reading "Wahoo" again for probably the 10th time. One thing our game lacks is historical realism that would make submerged static hunting viable since we play against AI.



It might work better than it should. In SH4 your view doesn't improve when your higher. Did you ever play SHCE? You could actually see farther when you raised the scope higher (or surfaced).

The other factor missing in game is ocean currents.

True. Another thing is the sea state. I remember O'Kane describing how in rough seas, there was "green water coming over the bow", causing them to waste fuel. I think this is a big part of the reason fuel is less of an issue in this game. Something else that was modeled much better in SHCE.

In such shallow water it's a dangerous game. I go in at night and attack and slip back to the deeper edge during the day and static hunt where I can still pick them up on sonar.

I agree. I've come to the conclusion that operating in shallow/coastal areas is fundametally different than deep water ops. O'Kane used the term 'horizontal evasion'; if you cannot use vertical evasion, all you got left is horizontal evasion. :DL

I just finished OPERATION DRUMBEAT recently. U-boat ace Hartigen would roam around wreaking havoc at night, then go back out to deeper water before daylight, submerge and just lay there resting until the next night. It was a shooting gallery; no trouble finding enough targets there.

[TorpX]

Pardon for the double post.

A couple of points here.

First a sea lane is not a narrow straight line even in the heavily traveled choke points. Markassar Strait is about 50 nm. wide. Luzon three times that.
Shipping lanes are no doubt about the same. You can sit in the center and still leave more than enough room for convoys to sail right by. Why give up the higher percentage for contacts just to save some fuel that is for the most part not an issue.

The math I used does not require a particularly wide or narrow sea lane. You can use different figures with these calculations and get substantially the same results. Fuel not being as much an issue is due to shortcomings in the game. In RL rough weather would slow you down much more. Even as it is when I am playing an S-class, fuel is indeed an issue. If I cruised continously in an S-class, it would be a short and unhappy patrol.

Second ships and convoys don't run straight courses they zig zag and can very easily sail right past you. Again a dynamic search will increase your chances of making contact and I would think the increase would be greater than what your figures suggest. The zig zags put them in your contact zone longer than a straight course would. The course changes reduce their overall progress on their base course. I do your yo-yo across the lane almost exactly as you describe but I'm also moving North or South. I described this in my second post.
I'll grant you targets zigging will give you more of a chance to detect them, but this doesn't fundamentally alter the math.
Again your giving away contacts to save fuel you most probably won't need.
I would say you are giving away contacts by wasting fuel and terminating the patrol prematurely.

Third Radar. 20 nm. range Your search area doubles and enabling you to cover most of area of a choke point if you're moving.
I'm not disputing the usefulness of radar (or sonar or anything else). Anything that doubles your detection range will double your chances, likewise anything that halves your detection range will halve your chances. This is true whether you are moving or not. Radar really has nothing to do with it. If you want to compare a radar equipted boat to one without radar, the radar boat will obviously win.

In any case, if you have a 20 nm radar, you can cover most of the area of a choke point even if your not moving.

If I'm in a dead area I'm going to patrol in a way that searches the greatest area in the shortest amount of time. Your not going to find much no matter which method you use.
OK, lets say you arrive at your patrol area on monday. No matter how quickly or intensely you search search your box. You will have to do it again tuesday, and wednesday and thursday....... However quickly you search, you cannot pull the targets to your location. If the area has an average of 2 ships transiting each week, it will take weeks to obtain a good number of contacts. And it is unlikely you would find them all. Realistically, most areas would not give you a contact every day, but by continuously cruising you would be burning a lot of extra fuel each and every day.
Your mission is to interdict shipping not stay on station for 60 days. They have other boats to replace you in that area.

I'm wanting to RTB knowing I gave myself the best opportunity to have success.

And when I get there I'm going to say "I one of the top guns and don't send me to the Marshals again." I'm sure they will listen. :D

But I do see what you are saying and your points are well taken, I can see several places that a static search might be the best tactic especially early in the war where fuel is a little bit bigger concern. Armistead has pointed out a couple as well.

Magic
[/INDENT]

Look, I can see your just a bit skeptical. ;) I am not trying to convince you to do it my way, but the math is the math.

The bottom line is a moving search is not as big a help as you like to think. When you are moving to the east, targets can slip by to the west, when you move to the west, targets might slip by to the east. If you go farther to the east to "cover more ground", a target could go past in the center or the west. You cannot be in two places at once, nor can you hasten or delay their arrival.

[gi_dan2987]

So what is the MOST optimal search method, please let me know, because right now I'm driving around in the Marshalls about ready to head to the area between Rabaul and Truk. I've only Sunk Nibu Maru in the Marshalls, and that was because I picked up a hydrophone contact while surfaced.

[Rockin Robbins]

Pardon for the double post. Look, I can see your just a bit skeptical. ;) I am not trying to convince you to do it my way, but the math is the math.

The bottom line is a moving search is not as big a help as you like to think. When you are moving to the east, targets can slip by to the west, when you move to the west, targets might slip by to the east. If you go farther to the east to "cover more ground", a target could go past in the center or the west. You cannot be in two places at once, nor can you hasten or delay their arrival.


You're confusing yourself by uncalculable random effects. If you are standing still they can miss you in any direction. If you are moving the same is true. You can't count the ones you miss. That's the defect in your method of calculation.

It is much better to think of searching in the same way Eugene Fluckey of the Barb did. He spent a lot of time explaining the situation, so I'm going to condense it.

The fact is, we don't know the disposition of the enemy on the ocean. If you are static in the middle of the horde, you're going to be successful. If you're static in a vacuum, you're coming back with a goose egg.

So you say, if you get a goose egg in 24 house, move! That's fine. Murphy's Law says you just moved from the next hot spot.

The only thing we can say for sure is that in any moment in time, the enemy is distributed in an unknown array over the surface of the ocean.

According to Fluckey, and I agree, the odds of finding a target approach unity when the distance between your sub and a target is within sensor range. So your job is to get within sensor range of as many targets as possible in a 24 hour period.

The corollary of that statement is that the number of targets you encounter is directly proportional to the number of square miles of ocean surface you search each day.

Let's do the math! You're static with a visual search radius of about 5 miles and a sonar search range of 20 miles on a good day. So you're searching a circle 20 miles in radius. The area you've searched is 3.14*20^2 square miles or 1,256 square miles.

Let's move out! We'll assume a 20 mile range for our radar and we're moving on the surface for 24 hours at our best fuel economy speed of 9 knots. Now your searched area approximates a rectangle 40 miles wide and 216 miles long. That's 8,640 square miles.

Since the enemy is moving and the effect of that movement is random we can safely ignore any effects on our results. Our movement will bring as many targets in range as it will leave beyond range. Therefore the comparison in the number of targets we develop can be expressed as the ratio between the two numbers of square miles searched.

So you are 8640/1256 times more likely to develop a target when moving. That is 6.88 times more likely. Another valid way to interpret the data is that a patrol during which you are actively searching at 9 knots, you will develop 6.88 times more targets in the same number of days as you would be searching statically.

But that is not the entire story. There are monstrous advantages to searching on the surface as opposed to searching submerged. Of most importance is the value of fully charged batteries. They can save your life, you know!

[gi_dan2987]

Therefore I choose to surface patrol :)

[TorpX]

You're confusing yourself by uncalculable random effects. If you are standing still they can miss you in any direction. If you are moving the same is true. You can't count the ones you miss. That's the defect in your method of calculation.
Not true.

It is much better to think of searching in the same way Eugene Fluckey of the Barb did. He spent a lot of time explaining the situation, so I'm going to condense it.
Fluckey did a lot of unorthodox things. As I recall part of his efforts involved probing/ raiding coastal anchorages where enemy ships were hiding out during the night. Is this what you are refering to? Looking for anchored ships or raiding coastal locations is not quite the same as searching for ships moving thru an area.

The fact is, we don't know the disposition of the enemy on the ocean. If you are static in the middle of the horde, you're going to be successful. If you're static in a vacuum, you're coming back with a goose egg.
How does this invalidate anything I said?

So you say, if you get a goose egg in 24 house, move! That's fine. Murphy's Law says you just moved from the next hot spot.

The only thing we can say for sure is that in any moment in time, the enemy is distributed in an unknown array over the surface of the ocean.

According to Fluckey, and I agree, the odds of finding a target approach unity when the distance between your sub and a target is within sensor range. So your job is to get within sensor range of as many targets as possible in a 24 hour period.



The corollary of that statement is that the number of targets you encounter is directly proportional to the number of square miles of ocean surface you search each day.
This is only true if you are searching for things that are not moving. While you are searching one end of your area, targets can move through the other and you'll never know it. Moving from one part of an area is not the same as being in both places at once.

Let's do the math! You're static with a visual search radius of about 5 miles and a sonar search range of 20 miles on a good day. So you're searching a circle 20 miles in radius. The area you've searched is 3.14*20^2 square miles or 1,256 square miles.


Let's move out! We'll assume a 20 mile range for our radar and we're moving on the surface for 24 hours at our best fuel economy speed of 9 knots. Now your searched area approximates a rectangle 40 miles wide and 216 miles long. That's 8,640 square miles.
Again, the square area is not what is important. If you were trying to find sea shells on a strip of beach, this would work ok. You could search an area, cross it off your list and move on to the next section. However, if the "sea shells" have the ability to move out from the water to the beach, and back into the water again, you will not be able to find nearly as many. They would be moving about in sections that you had "cleared". Your search efforts are only effective if there is a target nearby at the moment you are there. If the target moves thru either before or after you go by, you won't find it. Based on your analysis, it doesn't matter how fast enemy targets move, or if they move at all! An enemy cruiser moving at 30 kts could be found as easily as a drifting barge. You should see this is obviously not the case.
Since the enemy is moving and the effect of that movement is random we can safely ignore any effects on our results.

This is patently absurd if you think about it for two seconds.
Our movement will bring as many targets in range as it will leave beyond range. Therefore the comparison in the number of targets we develop can be expressed as the ratio between the two numbers of square miles searched.
If the first statement were true, it suggests there would be no difference.


So you are 8640/1256 times more likely to develop a target when moving. That is 6.88 times more likely. Another valid way to interpret the data is that a patrol during which you are actively searching at 9 knots, you will develop 6.88 times more targets in the same number of days as you would be searching statically.
OK, if this was really true, then you would get 2*6.88 times the number of targets in two days and 7*6.88 the number in a week. Do you really think just by moving at 9 kts this will get you 48 targets for every one I get in a single week? At this rate you could sink nearly 200 times as many targets in a month. Nice try, but your math does not hold up. Assuming that the number of contacts found will be proportional to the sq. area is a gross oversimplification.

But that is not the entire story. There are monstrous advantages to searching on the surface as opposed to searching submerged. Of most importance is the value of fully charged batteries. They can save your life, you know!
I never suggested submerged searching was better than surfaced searching. In fact the opposite is implied. Anything which increases your detection range (visual or otherwise), will improve your number of contacts by the same proportion. People seem to be reading things into this that I didn't write and don't intend. I never said it was better to drop anchor and remain motionless as if in a coma, or hide on the bottom of the ocean. Please, if you want to criticise what I've written, at least read it a little more carefully.




Ughh, too much typing. I'll try to find the relevent page in O'Kane's book.

[Stealhead]

I am not sure how the surfaced vs. submerged argument got into this.:hmmm:


@gi_dan2987 I would generally use a more active searching method while in open waters such as you find yourself and to use a more static approach if you find yourself in a choke point really though you should try every tactic find what works best for you.Sometimes also you can just have a dry patrol.

The sonar man being able to make passive contacts while on the surface is a game bug you could not do this in a real WWII sub so it is sort of a cheat(ever notice that spinning device of the deck of your sub that is the passive sonar head)

To me it depends if you use an active search but try to cover too large an area or use to high a speed I can agree that you are actually reducing the odds of making contact.

[magic452]

I'm not doubting your math, it's the tacit I'm questioning.

1 to 1.49 Your objective is to interdict enemy shipping in the Marshalls.
A 10 kn. search will give you more contacts in a given period if time.
Weather you get 12 contacts or 2 or 3 isn't all that important. If they aren't there they aren't there. What is important is to interdict as many as you can in the most efficient way possible and in the shortest time.

According to the math that is a 10 kn. search. There will be another boat along to replace yours. The objective is to cut off supplies to the Marshalls not stay on patrol longer. If I come home with torpedoes in the tubes but have 6 kills in three weeks patrolling I have done my job. Someone else comes homes with the same results but stayed 4 and a half weeks, not so good, at least one ship that I sank the other guy didn't and the Marshalls got resupplied. My patrol wasn't cut short costing contacts but the most efficient way to conduct business. My short patrol will be followed up by another boat to continue the operation and he will get the ship I didn't get in the next week and a half.

There are places where a static patrol is good, Tawi Tawi is one. Others have been mentioned.

I wouldn't be so quick to dismiss the zig zag thing. The contacts are now moving through the area at a reduced speed overall and I would think that would increase to ratio in favor of a dynamic search?


@ gi_dan If I'm in the Marshalls, I'd do my time and head to Truk or Rabaul as soon as I could.

Magic

[magic452]

I am not sure how the surfaced vs. submerged argument got into this.:hmmm:


@gi_dan2987 I would generally use a more active searching method while in open waters such as you find yourself and to use a more static approach if you find yourself in a choke point really though you should try every tactic find what works best for you.Sometimes also you can just have a dry patrol.

The sonar man being able to make passive contacts while on the surface is a game bug you could not do this in a real WWII sub so it is sort of a cheat(ever notice that spinning device of the deck of your sub that is the passive sonar head)

To me it depends if you use an active search but try to cover too large an area or use to high a speed I can agree that you are actually reducing the odds of making contact.

Stealhead please correct me if I'm wrong but at least Gato and above had some surface sonar capability as the sonar heads were mounted on the keel. As I understand it the game bug is that it works too good, above 10 kn. If I'm wrong I will have to change some of the way I play.


Magic

[Stealhead]

I am fairly certain it is even mentioned in "Thunder Below" and some others that it was not possible to use passive sonar(hydrophones) on the surface for the obvious reason that the head is on top of the hull and therefore not in the water.Now a ping using the active sonar was possible of course these are on the keel more or less so they are always in the water they could be retracted in real life as well.

The rotating device near the bow is the JT head and the man operating this actually sat in fore torpedo room later in the conning tower.The previous design was JP which I believe was located somewhere inside the upper hull I am not sure because my reference "US Submarines Though 1945" does not go into much detail about the older WCA/WDA sets nor the JT but goes into much better detail on the later war gear.But it seems that the passive part of sonar systems always where located on top of the hull and the active on the bottom(later war some times two on bottom one on top for active) excluding the S-boats where it was all on the deck.Later in the war they also had WFA which could also detect mines with great accuracy and was also much more accurate against ships but this is not included in the game.

In other words if you want to play more realistically then you cant use the passive sonar on the surface and in an S-boat you cant use any sonar at all fully surfaced.In a fleetboat you can use active sonar on the surface though it was done commonly I am pretty sure I recall its use being mentioned in "Thunder Below" and "Wahoo" of course it wold be used with great care and very briefly something the game does not really simulate is how the density of water effected the active and passive sonar of the submarine sometimes very strongly in a negative manner.(reducing range and accuracy) What helps you hide from the IJN also hinders your sonar or it should.

look at this a little about the JT.You like math?Click on the Sonar home page at the bottom ans start from the first page of the manual you'll see tons of it.
http://www.hnsa.org/doc/sonar/chap13.htm

[Sailor Steve]

I've always had a problem with sonar, even active sonar, working on the surface. The problem I have is that if sonar works for a surfaced submarine then it should also work for a surface ship against other surface ships. I served on a destroyer and I don't recall ever hearing of anything like that. Of course I wasn't a sonarman, so maybe they just didn't tell me about it. If there is information that they used it and it worked, then they did use it and it worked.

I'm just sayin'.

[Bilge_Rat]

The issue with sonar not working on the surface is not where the heads are located, but basically a problem of ambient noise and the limitations of the SH engine.

To simplify the issue, to be able to hear sounds which are far away, you must not be close to a source of noise which is loud enough to cover far away noises. For example, if you are standing next to a noisy engine, then that is all you will hear. If you turn off the engine, you will be able to hear fainter noises which are farther away. The noise of the engine nearby masks fainter noises which are farther away.

The same in a sub, if you are travelling at 2 knots 100 feet deep using electric motors, you generate relatively little noise and are able to hear sounds from farther away. If you are travelling at 10 knots on the surface using Diesel engines, you generate a lot more noise. In addition, you also have the turbulence caused by the ship moving at the surface which will also render the heads less effective. The noise is the reason why U-Boats running their diesels on Snorkel were unable to hear anything on sonar even though they were underwater.

In theory, a motionless sub could use its sonar on the surface, but then we run into the limitations of the SH engine. In SH, Sonar is an on/off switch: when ships are within a certain range you hear them, when they are outside you don't. In SH 3/4, this range is not affected by speed, although in SH5, speed will degrade the effectiveness of Sonar. So modding the Sonar so you cannot use it on the surface is a practical solution to place the player in a similar situation to a WW2 sub skipper.

[Stealhead]

That sir makes absolutely no sense if the passive sonar head is above the water then there is no way on this earth that it is gong to be able to hear anything the same would apply to the S-boats all of the sound gear is on the deck so if you are on the surface and you can see the gear in the air then it can not possibly be in the water to enable it to hear anything the location of the gear 100% has an effect if said gear is on the deck on the surface and not in the water.In fact a sub on the surface trying to use sound gear which is above water will hear nothing.

I agree that there are limitations in the SH4 simulation but it makes perfect sense for a piece of sound gear not actually being submerged in the water not to be able to hear what might be in the water so the SH4 sound man is evidently Kent Clark and has super hearing.You seem to be confusing various things causing interference in a situation where the sound gear actually is in the water.I am talking about sound gear actually not being in the water and with US Navy subs the passive gear was above the water while the sub was on the surface but the active gear exluding the S-boats was below the water while surfaced.So active sonar while surfaced yes passive sonar no though I doubt the active sonar would be very accurate in such a setting.


EDIT: ok I found this in the very extensive US Navy Sonar manual from HNSA the manual Bilge Rat posted is also from HNSA but is from a different manual from US Navy Sonar pg.241;

"Submarine listening equipment is designed to receive and reproduce underwater sounds-both sonic and ultrasonic-for the purpose of identifying the sounds and locating their sources. Sonic sounds (below 15,000 cycles per second) are made by propellers, engines, rudder motors, pumps, gear wheels, and many other devices. Ultrasonic sounds originate mostly from high-speed propellers. The bearings of the sources of sounds usually can be determined, so that targets can be located without the use of echo-ranging gear."


"Model JP Listening Equipment

DESCRIPTION
Models JP-1, JP-2, and JP-3 equipments are used on submerged submarines to obtain bearings on other vessels by directional detection of underwater

sounds. They can be used also to listen for own ship's noise. Models JP-2 and JP-3 differ from JP-1 in the amplifier circuits. Models JP-2 and JP-3 are alike except for the method of mounting the hydrophone."

Which basically means that if you are only using the keel mounted ultrasonic heads you will not hear slower props in the sonic range as well or at all so you will hear something with a fast screw like a DD but not a slower screw or perhaps not as far or clearly.So in other words we are both wrong and both right though to get the full sonar picture the sub would need to be submerged.

[Nisgeis]

The early war fleet boats with the WCA gear had four sonars underwater:

QC/JK - QC for echo ranging and the JK for passive listening. I believe the JK was ultrasonic and not so good for long distance (but quite good on bearing accuracy). Could not be used at the same time as they are mounted on the same head on reciprocal bearings.

QB - echo ranging with a wider frequency band than the QC

NM - Echo sounding equipment.


Note 'Q' is for a range projector/listener and 'J' is a passive listening device and 'N' is an echo sounding device (for depth).

They also had JP in the Forward Torpedo Room and the head was above the waterline and was in the sonic range. JT sonar, which was a later version had better bearing precision as it received both sonic and ultrasonic and a few extra features. Need to be submerged to use these.

EDIT: The sonar manual, advises the operator to continue listening when on the surface when conditions permit, e.g. weather and speed - as has been said previously water rushing over the sonar head drowns out other noise and also sea state plays a part too.

[Bilge_Rat]

That sir makes absolutely no sense if the passive sonar head is above the water then there is no way on this earth that it is gong to be able to hear anything the same would apply to the S-boats all of the sound gear is on the deck so if you are on the surface and you can see the gear in the air then it can not possibly be in the water to enable it to hear anything the location of the gear 100% has an effect if said gear is on the deck on the surface and not in the water.In fact a sub on the surface trying to use sound gear which is above water will hear nothing.

I agree that there are limitations in the SH4 simulation but it makes perfect sense for a piece of sound gear not actually being submerged in the water not to be able to hear what might be in the water so the SH4 sound man is evidently Kent Clark and has super hearing.You seem to be confusing various things causing interference in a situation where the sound gear actually is in the water.I am talking about sound gear actually not being in the water and with US Navy subs the passive gear was above the water while the sub was on the surface but the active gear exluding the S-boats was below the water while surfaced.So active sonar while surfaced yes passive sonar no though I doubt the active sonar would be very accurate in such a setting.

well obviously I was not talking about sonar equipement which is outside the water, many fleet boats had their sonar heads located under the hull.

[Stealhead]

You did say location had no effect though which is not correct if that position was out of the water.Like wise when they went to the WCA set from the older QC/JK as on the S-boat there was some concern about use of the active heads while near the bottom which was not an issue with the QC/JK deck location.The WCA and later heads where retractable but it was not uncommon for them to get damaged anyway.The other thing to take into consideration is that the sub would have to be fully submerged to get full use of any one of the various systems to get an accurate picture using sonar they needed the full ensemble and there fore had to be completely submerged.

The sonar heads you mention are the active ones the ones that ping they are not the passive "hydrophone" type that allow you to listen to screws in the water.If you look at that link I posted you'll see that there where two active heads on the keel and one for sounding depth and the passive head is above the deck the JT head.

[Nisgeis]

JK is a passive hydrophone.

[Bilge_Rat]

You did say location had no effect though which is not correct if that position was out of the water.

I presumed that I did not have to point out that a receiver in the air cannot hear noises under water, that is after all, pretty basic.


The sonar heads you mention are the active ones the ones that ping they are not the passive "hydrophone" type that allow you to listen to screws in the water.If you look at that link I posted you'll see that there where two active heads on the keel and one for sounding depth and the passive head is above the deck the JT head.


no, the JK/QC and QB heads located on the bottom of the hull are receivers.


http://www.hnsa.org/doc/fleetsub/sonar/chap5.htm

[joegrundman]

Interesting discussion TorpX (your part of it, anyway)

I'd been wondering about that very thing actually.

[Stealhead]

I presumed that I did not have to point out that a receiver in the air cannot hear noises under water, that is after all, pretty basic.





no, the JK/QC and QB heads located on the bottom of the hull are receivers.


http://www.hnsa.org/doc/fleetsub/sonar/chap5.htm

I am referring to the S-boats not the fleetboats on the S-boats the QC/JK is all mounted on the deck.If you would please view the 23rd 40th and 45th pictures on this link you will see a large transducer below it is a bar this is part of the system this is the JK/QC that you are trying to tell me is on the keel but not on any S-boat is not. http://pigboats.com/subs/s-boats4.html.







To be entirely honest I am getting different answers as to what is possible from different sources which makes me fell as though one cant say for certain what was possible but seesm that in order to get the full spectrum of passive sonic and supersonic sound gear the sub has to be completely submerged.In my onion this is a good question ask DaveyJ576 the most knowledgeable member on Subsim when it comes US Navy Sub technology this question What exactly was a WWII US Navy sub capable of dong with its sound gear on the surface and below for that matter? The problem with military technical manuals (I know from personal experience) is that can be overly optimistic and do not always represent what is done in the field for all we know the Chief of the boat may have tossed it overboard often they are written by engineers not by those actually using the gear in the field and truly knowing the in and outs.


Edit:
I did find on this HNSA page of US Navy Sonar; http://www.hnsa.org/doc/sonar/chap13.htm

"Submarine listening equipment is designed to receive and reproduce underwater sounds-both sonic and ultrasonic-for the purpose of identifying the sounds and locating their sources. Sonic sounds (below 15,000 cycles per second) are made by propellers, engines, rudder motors, pumps, gear wheels, and many other devices. Ultrasonic sounds originate mostly from high-speed propellers. The bearings of the sources of sounds usually can be determined, so that targets can be located without the use of echo-ranging gear.
The original J-series listening equipment was designed for use on submarines. Most modern listening equipment, such as the JP and JT, is designed for patrol craft, picket boats, and submarines. The JP-series listening equipment is now in use on submarines as a unit of the JT equipment."

To me this seems to say that we are both wrong/both right as one could use the part of the passive system but only the super sonic(which would now be called ultra sonic) side of the system would be usable on the surface and you would be unable to hear slower speed screws very well and the supersonic range was very short only a few thousand yards at best so you would only be getting half the picture on a good day.

[Bilge_Rat]

Stealhead,

We may be talking at cross purposes, I agree with you that a WW2 Fleet Boat would not be able to use its sonar on the surface, except in very limited ideal conditions.

[Stealhead]

Stealhead,

We may be talking at cross purposes, I agree with you that a WW2 Fleet Boat would not be able to use its sonar on the surface, except in very limited ideal conditions.


I was thinking this as well.I actually found a very interesting page on the HNSA site that has a whole mess of recordings of subs some of them are recordings of different ships screws and there is a sound recording from the conning tower of the USS Sealion as her crew attacks the IJN Kongo.

http://www.hnsa.org/sound/

[TorpX]

I found the relevent pages in O'Kane's book. I've quoted him at length because I consider him to be very knowlegable and so the reader can understand he put a good deal of thought into his strategy. This is from p54 of CLEAR THE BRIDGE, (I marked the most relevent parts in blue):



]... Dawn came and we continued our search, now augmented by the search periscope, with Tang still on the surface, lying to and maintaining quiet.[/FONT]

This was a far cry from accepted submarine doctrine, which dictated having way on the boat, but what is doctrine anyway? I believe it is a set of procdures, established through experience, that provides a guide. But doctrine should be flexible, never rigid, for circumstances often dictate complete departures. Our situation that day was an example of such curcumstances.

In order for us to utilize speed in searching, it was first necessary to know the general direction of the enemy's movement. We could then proceed on a very wide zigzag ahead and thus cover a broader front as the enemy overtook. But we were presently in an open-sea area, and enemy ships might be on any track, though the northwest-southeast courses passing through the western part seemed more likely. No amount of running around at our available speeds would increase the probability of sighting the enemy. In fact, to do so would only make us a target for a submerged enemy submarine and would blank out our sound gear with our own screw noises.

Tang was lying to in the center of a circle some 20 miles in diameter that we had searched by radar and sound during the three hours before daylight. It was clear of any enemy. The only planes that could reach our position were patrol bombers. We could sight them and dive before they sighted us, for our diving time when lying to was only five seconds longer than when proceeding at 15 knots. The only real danger was from a submarine, but she would first have to come into the area undetected by our sound, radar, scopes, and lookouts. Then she would have to conduct a many-mile submerged approach. This would call for considerable submerged speed. Our soundman, with no interference from our own propeller noises or from other machinery, would detect her screws before she reached an attack position. The foregoing was not just conjecture or we would not be staking our lives on it.

In addition, lying to while in this open-sea area would use only the diesel fuel necessary for normal living, just a fraction of that consumed when cuuising at one-engine speed. The oil we saved would be available when it might really be needed in persuing the enemy.

There were, of course, the alternatives of a submerged patrol with high periscope searches or of periodic surfacing. Neither of these would insure the coverage we wanted, nor would they save the fuel, as we would then be charging batteries nightly.

We shifed our patrol station 20 miles each evening so that if we were detected, shipping could not just be routed clear of a single spot. At the same time we were working south near the western boundary of our assigned area. ...
[/QUOTE]




From what O'Kane said, I think it is clear that he either worked out some of these search problems mathematically, or learned from intructors who did. Possibly, someone will find some USN charts/manuals/documents that deal with this issue.


From joe grundman:
[QUOTE]Interesting discussion TorpX (your part of it, anyway)

I'd been wondering about that very thing actually.


Thanks.
I read OK's technique just as I started getting into subsims, and have used his tactics. I'm sure it is possible to have good patrols with other methods, but I still think OK's method is the best for searching in open-seas, where you have no assurance of finding plentiful contacts. I haven't read all the available literature by any means, but I believe at least a few others made use of similer strategies.