submarine survivability again

[m10bob]

On somewhat a similar note, and also according to Clay Blair's SILENT VICTORY, one of the things which assisted allied subs in the Pacific till maybe early '43 was that Japanese DC's had a ridiculous pre-set depth of something like 40 feet(?), as they did not feel subs would be operating any lower when intercepted.
IIRC individual Japanese skippers had to correct this manually, (and against orders) to achieve success in other than shallow water.

[herwin]

ORIGINAL: m10bob

On somewhat a similar note, and also according to Clay Blair's SILENT VICTORY, one of the things which assisted allied subs in the Pacific till maybe early '43 was that Japanese DC's had a ridiculous pre-set depth of something like 40 feet(?), as they did not feel subs would be operating any lower when intercepted.
IIRC individual Japanese skippers had to correct this manually, (and against orders) to achieve success in other than shallow water.

Actually not ridiculous at all. That was about optimal. Asdic wasn't very good at localising submarines.

[vettim89]

I have to agree that the problem is not with the subs but with the accuracy of the DC. Not being a modder but thinking about it, I think this is where the change should be made. Lethality of DC's is probably about right.

As far as Mousetrap/Hedgehog goes, there are several reasons these weapons were more accurate. The first being that the SONAR operator could feed information to the bridge/CiC as to the subs movement. Hull mounted sonars were blind in an area approximately 30 degrees to either side of the stern. With a DC attack the attacking ship would lose contact with the sub as it passed over it. A wise sub commander would know this and would then time a sprint evasive maneuver just as the ship passed over hoping to not be where the attacking ship's commander had projected the sub to be. Becasue Mousetrap/Hedgehog were Ahead Thrown Weapons, the attacking ship remained in contact with the sub during the attack. the second factor was that the projectiles from this weapons had a very fast sink rate - much faster than DC's. Therfore when the weapons were fired the time to target was much lower. The third factor was that the warheads were direct contact weapons. That is the caused damage by directly impacting the sub's hull. While hits may have been rare, they were devastating. A single 3 " hole in a submerged sub's hull was a big problem.

The other factor that may be playing into the equation is ease of presecution. Is it too easy for DD's et al to find the subs. This was not an easy thing in WWII. The SONAR's were not very accurate and very short ranged. Further, becasue active SONAR was really the only truly effective form in this era, the ship using it gave away its position. The sub drivers knew the approximate position of the ships hunting them and that gave an immense advantage to a sub skipper when trying to get aware.

[Historiker]

one may try giving DCs a dud rate?

[bradfordkay]

I would have liked to see SONAR modeled in the game, with its effectiveness based upon both type and crew experience. That would reduce the number of sightings to some degree, and if combined with a reduction in DC acuracy would have created a more realistic sub warfare model IMO.

[ChezDaJez]

ORIGINAL: herwin

ORIGINAL: m10bob

On somewhat a similar note, and also according to Clay Blair's SILENT VICTORY, one of the things which assisted allied subs in the Pacific till maybe early '43 was that Japanese DC's had a ridiculous pre-set depth of something like 40 feet(?), as they did not feel subs would be operating any lower when intercepted.
IIRC individual Japanese skippers had to correct this manually, (and against orders) to achieve success in other than shallow water.

Actually not ridiculous at all. That was about optimal. Asdic wasn't very good at localising submarines.

Correct. WWII active sonars had a standard deviation error of approximately 100-150 yards when the searching vessel was within 1000 yards. Passive sonar was even worse especially if it was from a sonobuoy as their was no way to determine bearing. A ship with a steerable receiver could determine a quadrant but bearing accuracy was very poor.

m10bob:

You are on the right track but the Japanese set depth charges based, in part, on the depth capabilities of their own subs. That meant most of their charges were set to 200 feet or less. A US sub was relatively safe below that depth.

An interesting side note to this... a congressman (IIRC) from Illinois conducted a junket tour of the Pacific in 1942 and discovered this fact during an informal briefing. He returned to the States and told a newspaper reporter that our subs were not in danger due to this. The newspaper (Chicago Times?) reported this and the War department became very upset. It has never been determined if the Japanese ever received this information.

Chez

[el cid again]

ORIGINAL: ChezDaJez

Nevertheless- it only solves the cost problem. The sub is still to easy to sink - ah - but we can do this: use crush depth INSTEAD of test depth - THAT will work.

I think that you are missing the key point. Subs SHOULD be easy to sink... they were fragile things. In the game, it is the accuracy of the attack that primarily results in high subs losses, not the way the sub is modelled. And this involves external factors.

Let me explain. IRL, a submerged sub often escaped serious damage despite enduring multiple depth charge attacks. If you read the Clay Blair's "Silent Victory", he relates that U.S. subs were depth charged on a significant number of occasions without incurring substantial damage. In the Atlantic, most German subs also endured mutliple attacks and remained operational. Indeed, in most occurances, it took multiple attacks over a period of hours, sometimes days, to bring about the destruction of the sub. Depth charges attacks were one of the least accurate attack methods employed. Even after the advent of other ASW weapons such as the Hedgehog, the accuracy of the attack was still poor due to the inherent difficulties of using sonar to accurately predict a sub's location and depth sufficiently to bring about a successful attack. The primary advantage of the Hedgehog was that it did give confirmation of a hit.

In the game, attack accuracy appears to be too high. And I believe this is because depth charges are modelled similar to bombs where each individual weapon is given a chance to hit rather than the pattern as a whole. So the more DCs dropped in a single attack, the greater the chance of multiple hits in the game when in reality the most hits that could be expected from any one DC attack was one. This was due to the need to cover a large area with a DC pattern to offset the inacuracy of the attacking ship's sensors.

In the game, it is not common for a Japanese sub to remain operational after a DC attack. Indeed, they are sunk about 40-50% of the time. At least that has been my experience in my CHS 159 game. This is again related to the accuracy of the attack and to the large number of DCs in the patten employed by allied ships. I have seen instances where a sub has incurred 4-5 DC hits from a single pattern. Not quite historical. U.S. subs have a far better survival rate but this due more to the small damage factor of the Japanese weapons and fewer DCs in the pattern.

On the other hand, the lethality of the weapons themselves actually appear to be understated. Few things upset me more that to see a comment on the combat replay that sub XX has taken a direct hit by a DC and then find that flot damages is only on the order of 30-40. A direct hit should result in the destruction of the sub. Breaching a pressure hull on a submerged sub virtually guarantees its destruction.

We also have the issue of damaged subs foundering on their return to port which increases losses. IRL, few subs were lost in this manner unless as a result of another attack. To have a sub founder 3-4 days after an attack is ahistorical. I can not think of a single Pacific area sub that did. Not to say it didn't or couldn't happen, but I know of no case where this was true.

Most of the time it is Allied players that complain of high sub losses. This is not a JFB vs AFB thing. We overlook that Japanese players tend to incorporate histories lessons into ASW tactics. That is they assign large numbers of search planes and employ H/K groups to prosecute detected subs. Some people call this gamey, some just call it ahistorical. I agree with the latter but then the game itself becomes ahistorical the moment the first turn is run.

So, no. I don't think there is an issue with the sub model itself. I think the main issue lies in the high accuracy of the attack.

A bit rambling I know but I have to leave for work.

Chez

There is considerable merit to these comments - even the first one - which I disagree with. Let me comment on the comments:

1) While a submarine IS indeed very vulnerable IF you hit it - a single hole in the pressure hull is often a big problem - they are not "easy to sink" because you cannot hit them. Even surfaced they are difficult targets - small - painted so you can hardly see them at all - low to the water - and very slender - meaning it is not hard to miss when you see them from the one aspect that gives you a lot to see - from the side.
Underwater you cannot usually see them at all (except from an airplane in daylight and good visibility - IF the sub is shallow - AND IF water conditions are right as well - a lot of ifs). Except with Hedgehog type weapons you must guess the depth - and so you often are wrong in depth even if you get the right target bearing and range. And since there is sinking time - the sub can turn or reverse AFTER weapons release - and you have no control over the amount you are going to miss.

2) We have never (in ANY form of WITP) used the REAL depths submarines used tactically. And the apparent "uniform standard" of test depth is NOT uniform in fact - because different nations define it differently. So we get better relative submarine survivability if we use the design depth - calculated from the test depth using national data. Since this ALSO gives us less lethality - it moves us toward solving the problem of submarines are too easy to sink.

3) The way GG's code works, attack factors are multiplicative - so it does not matter which of the variables are changed - the net outcome is the same. Changing the depth should have the same effect as changing accuracy does. But accuracy relates to the attacking weapon - while depth relates to the target. Here we are using a mechanism - an instrumentality - that should help us both get more survivability and also a better relative survivability per nation and class. For example, German submarines will be harder to sink than others, something we would not get if we changed weapon accuracy per se. I think that is the right direction to go in.

4) I have a problem in RHS because of a compromise due to slot limits. This will be less an issue in AE no doubt. But one of my DC is also a bomb - and I don't want to mess with accuracy on a bomb. Since it is small - the smallest - we could probably ignore it as an issue - but ideally I want all weapons to use the same standards. And right now - bombs and DC apparently are using a common sccuracy standard. IF there are any actual technical definitions ( I still say we need a tech manual ) - that might help us decide what to do, if anything?

5) Stock and CHS experience will not reflect real life or RHS very well: Japanese patterns got quite as large as American ones did (on true ASW ships) - and in RHS you might see a US sub subjected to patterns of 10 or 12 later in the war. The only sense in which they are less lethal is that they are smaller charges and have fewer depth settings. IRL the problem was also tactical: the Japanese usually underestimated what to set depth wise: when they didn't do that we could be in trouble. I think that is below the level we can deal with - that die rolls and abstraction must apply for us as mod designers: a good role means they set the depth right sort of thing.

[el cid again]

ORIGINAL: m10bob

In Steel Panthers I was able to pretty much simulate those small "Goliath" type robot tanks by giving them a size of "0", because ability to spot and hit was altered by the factor of size.
I wonder if this might have any relevance to the subs in WITP? IE, can the numbers be altered to make them less visible?

.

FYI Goliath is in RHS - but in a completely different sense than described above. Goliath is considered to be part of the definition of a certain kind of assault squad - and it is found in numbers only in "electric" independent engineer regiments. In CVO and BBO (i.e. strictly historical) scenarios there is only one: the 7th. In EOS family there is also the 27th.

[el cid again]

ORIGINAL: Historiker

ORIGINAL: el cid again

Using time as the basis for cost means that gigantic submarine aircraft carriers cost less than many lesser vessels - since they were built fast.

Using displacement as the basis for cost is similar to all other ships - but then the game costs get excessive. We would have 18 for 180 days in the example above - instead of 8 for 80 days. The composite system results in lower cost impacts while preserving relative differences between classes.

Yet another factor might be that sub transports designed as such - simple vessels - cost half what a regular attack sub costs.

Opinons requested.

I already explained it once...


Durability is in witp:
1. Survivability
2. Building costs
3. Active Building time (the time you have to pay for them)

Lets take a CL with a durability of 30. In which ratio you split it is your choice, but just to show you how to calculate:
As 1 is irrelevant because the survivability is given with the first update, the 40 are divided into bowth 15 for 2. and 15 for 3.

Building costs are:
2a Workers needed
2b Material needed
2c Length of the slipway or drydock needed

Ok, now you take Sub XY and compare it with the CL:
2a: 50% needed
2b: 25% needed
2c: 75% needed
3: 60% needed

Now simply adding the numbers and you have the needed durability for the SS.

2,5(2a)+1,25(2b)+3,75(2c)+9 = 16
In this case, the subs needs to have a building durability of 16. AFAIK, building time in witp is 4 times the durability (so 16 means 64 and 30-120 days to pay), so this has to be mentioned as well, but on this basis, you may calculate the building durability.

Moreover; foreign subs mustn't have a greater building durability than 1 as they aren't produced in Japan's shipyards, so Japan doesn't have to pay for them!

Although I speak English fairly well, originally joined the USN in the submarine field as a technican, became an engineer and studied design of ships (including forinsic examination of WWII submarine designs) - I was not able to follow this. I do not understand what you are trying to say - and it needs to be explained again from scratch or I cannot use it. There may indeed be somethign here we can and/or should be using - but I don't get it. Sorry.

I DO understand what WITP durability is - but here we are cheating - we can ignore build cost and time for the submarines - except for Axis boats that do not start day one. For operations we use depth based durability onlly. But for BUILDING Axis subs not already extent - what should we use for durability - ONLY from a cost to build point of view?

[el cid again]

ORIGINAL: Nikademus

ORIGINAL: Historiker

I already explained it once...


Durability is in witp:
1. Survivability
2. Building costs
3. Active Building time (the time you have to pay for them)

don't forget;

4) repair

True. But here RHS is adopting a new standard for PLAYING - durability ONLY based on DEPTH rating. Cost to repair will be whatever it is for that rating.

We need not worry about building cost or time with a single exception: Axis subs that don't start the game. For them we use a DIFFERENT class definition with a value based on what we want build cost and time to be. Then they convert to the class with the durability we want.

[el cid again]

ORIGINAL: herwin

Submarines should not be easy to sink--they're about as robust a seagoing vessel as is built--what other kind of ship can stand the water pressure 100 meters down? Experience was that a depth charge had to be no more than about 8 meters from a sub when it exploded to do significant damage. Operational results also indicated that once a sub had dived to about 30 meters, it was extremely hard to kill.

Bombing accuracy in the game is also excessive. Experience with level bombing was that an average of 3% of the bombs dropped on ships at sea hit. One in nine airborne torpedoes hit--the Japanese experts got two in nine early in the war. Two in nine bombs dropped by dive bombers hit on the average. Allowing the experts to double their percentage (and doing the same thing for ships in harbour) still doesn't produce hit rates like those seen in the game.

Lots of things matter.

Fujida got Japanese Kates able to hit a non moving large ship target 8 times in ten - for a new vic of 5 bombers. That is the same thing as saying 16 per cent hit rate. That from HIGH altitude - necessary so their wierd 16 inch shells cum bombs would have the energy to penetrate a deck.

Bombing at low altitude is a lot more effective - and bombing a ship using skip or glide bombing profiles is virtually certain to hit if the aimer has the target speed set right. Players bomb too low - before anyone thought of it - and the game code is set so that very low bombing simulates skip bombing - so the model is right - but players are using it wrong. [This was explained years ago on the UV Forum]. The only solution would be code changes - date limiting the low altitude skip bombing might be one way.

I do agree submarines are hard to sink - in spite of the fact they are potentially badly damaged if you hit them. Submarines are in some respects like tankers - lots of pumps, compartments, compressed air and ways to control damage. And expert crews who quaiify on every station on the boat (in those days - only post war did some subs have parts of the boat some sailors could not enter - e.g. nuclear engine rooms).

[el cid again]

ORIGINAL: ChezDaJez

ORIGINAL: herwin

Submarines should not be easy to sink--they're about as robust a seagoing vessel as is built--what other kind of ship can stand the water pressure 100 meters down? Experience was that a depth charge had to be no more than about 8 meters from a sub when it exploded to do significant damage. Operational results also indicated that once a sub had dived to about 30 meters, it was extremely hard to kill.

Bombing accuracy in the game is also excessive. Experience with level bombing was that an average of 3% of the bombs dropped on ships at sea hit. One in nine airborne torpedoes hit--the Japanese experts got two in nine early in the war. Two in nine bombs dropped by dive bombers hit on the average. Allowing the experts to double their percentage (and doing the same thing for ships in harbour) still doesn't produce hit rates like those seen in the game.

Submarines may have been "robustly" built but that robustness had its limitations. A submarine operating at or near maximum depth is vulnerable, very vulnerable to even the slighest damage to her hull. And as the hull would already be stressed nearly to the breaking point from water pressure, an exploding depth charge's pressure wave could easily cause a fatal breech if close enough. And it doesn't have to be a large rupture. The failure of a 1" pipe at 400' is enough to seal the fate of most WWII subs. The flooding would be catastrophic and impossible to stop. Even if confined to a single compartment, returning to the surface would be no sure thing. And forget about blowing tanks in most cases. Even if the ballast tanks themselves aren't ruptured, most subs had little reserve buoyancy with ballast tanks full of air. The weight of a flooded compartment could easily override that reserve buoyancy.

The amount of damage a depth charge will do is directly proportional to the depth of the DC, the explosive power of the DC and the depth of the submarine. A depth charge exploding 8 meters from a hull would be fatal when that submarine is at periscope depth. At 400' a depth charge need not be nearly that close. A distance of 10-15 meters would be sufficient, especially if the boat were a pre-Balao class boat that used only medium tensile strength steel. And most Japanese boats were not nearly as robustly built as US boats.

But still, you seem to have missed the point. The point of my posting is that DC attacks are too accurate in WitP. The number of subs lost in the game has little to do with sub durability but does have everything to do with the number of hits achieved. And this is directly related to the accuracy of the attack.

And as you seem to feel the same way as I regarding bombs, then I assume you also feel the same way about DCs. DC patterns seem to use a similar method for determing hits as is used for bombs. That is each weapon's chance to hit is calculated individually. I believe the chance to hit for both bombs and DCs should be calculated by the pattern, not by the individual weapon.

Chez

I confirm that at deeper depths a pressure wave is potentially more dangerous. I don't think it is easy to get close enough however. The deeper a sub goes, the less likely the DC will be set for it. Below a certain depth it becomes IMPOSSIBLE to set for it (the exact depth varies with the DC - but you cannot set a DC for 100 fathoms if it has a 50 fathom limit).

I confirm that DC and bombs are treated the same way. It appears that in WITP DC are just strange bombs.

I agree that ASW weapons and bombs should be rated for patterns - but only a few are - and they have their own problem. A "cluster bomb" is rated as a smart weapon - which is probably wrong by itself - and as a smart weapon - it gets the SAME loatout at extended or normal range - which is certainly wrong. No one uses DC patterns - although I have proposed to do so - rate all ships in DC pairs - because all cases involve pairs. Even a ship with one DC rack will normally drop a pattern of two; a Y gun always fires 2 DC, and K guns normally are mounted in pairs - yielding 2 fired per pair. This would cut in half the number of apparent rounds used in the attack.

[el cid again]

ORIGINAL: herwin

ORIGINAL: ChezDaJez
...

But still, you seem to have missed the point. The point of my posting is that DC attacks are too accurate in WitP. The number of subs lost in the game has little to do with sub durability but does have everything to do with the number of hits achieved. And this is directly related to the accuracy of the attack.

And as you seem to feel the same way as I regarding bombs, then I assume you also feel the same way about DCs. DC patterns seem to use a similar method for determing hits as is used for bombs. That is each weapon's chance to hit is calculated individually. I believe the chance to hit for both bombs and DCs should be calculated by the pattern, not by the individual weapon.

Chez
And as you seem to feel the same way regarding bobms, then you must also feel the same way about DCs.

I agree, DC attacks are too accurate in the game. (In reality, it took about 1000 charges per German sub sunk.) Morse and Kimball, Methods of Operations Research, discusses the stats. The other half of the problem until 1943, was that killing a sub was a three-dimensional problem-DCs were fused to explode at a specific depth, and a fuse depth greater than about 8-10 meters was too deep for subs beginning to dive--the one's you had the best chance of sinking. Going from a fuse depth of 8 meters to 16 meters reduced your probability of kill by a factor of three, and if the sub had submerged more than 30 seconds before the attack, your pK was basically zero.

For proximity-fused DCs, the attack error was circularly normal with a standard deviation in each direction of about 100 meters, and the lethal area of a sub was about 1000 square meters. Working it all out, a 1944 DD had to lay a pattern of 13 proximity-fused DCs to get a 14% chance of sinking a sub at a known location. You can see why an average of 1000 proximity-fused DCs were expended per German sub sunk. It was several times worse earlier in the war.

And in general, the location of the submarine was both unknown and unknowable. Consider -

a) If you DID know where it was, it would usually move before a DC pattern could sink that far - and if you aimed for where he was you would certainly miss

b) If you DID know where he was, and you guessed his maneuver - you could aim so that they would be where you guessed - but it was a bet - and you had to guess right - from a set of several options (turn right, turn left, dive, rise, reverse, change speed, don't move at all).

c) Your chance of knowing his bearing was much better than your chance of knowing his range - the opposite of radar - sonar bearings are good within a few degrees - but ranges get messed up by lots of things - not all of which were then understood

d) You chance of knowing his bearing and range was much better than your chance of knowing his depth - almost no depth finding sonar existed - and depth was guessed based on doctrine, tactics, experience or mythology.

ASW is hard - it is still hard with much better equipment today - but it was not totaly impossible. USS England seems to have got it right. She sank an entire Japanese patrol line in a single operation. She was working in a group including a CVE and planes. Yet she did it herself. Even whey they tried to let another ship do the job - England ended up doing it. It appears it was possible to figure out where a target was - and to engage it successfully on the first try - but it appears likely this was very exceptional. In 1982 the NATO ASW specialists - RN - expended almost every ASW weapon in inventory in 200 attacks - 199 of which had NO enemy target at all - the last one did NO damage to the target. The target was TWICE able to shoot torpedoes at RN carriers though. It is hard to tell a submarine from a whale and other natural phenomena. It is hard to detect at all in some weather conditions - actually impossible sometimes. And the layer was not properly understood in that era either. Nor was sonar propagation theory. So sometimes things would happen they just didn't understand right - resulting in mis targeting.

One reason for 1000 DC per kill is most attacks were against some false target. |

Add to that - the enemy might deliberately give you a false target to shoot at.

Add to that - if you DID make an attack on a real target - you did NOT know what damage it had done. So you might stop attacking without killing the submarine - particularly if you saw oil or debris or both. How do you know you killed the beaste? [Answer - UNLESS you hang around for two days to see if he comes up - you don't. I want a way to do that in the game - but that needs code changes.]

[el cid again]

ORIGINAL: m10bob

On somewhat a similar note, and also according to Clay Blair's SILENT VICTORY, one of the things which assisted allied subs in the Pacific till maybe early '43 was that Japanese DC's had a ridiculous pre-set depth of something like 40 feet(?), as they did not feel subs would be operating any lower when intercepted.
IIRC individual Japanese skippers had to correct this manually, (and against orders) to achieve success in other than shallow water.

Which may or may not be good analysis. See above about how OUR setting was too deep - that your best shot was at a sub just submerging - for which you MUST have a very shallow setting. It was too shallow for a sub at depth - but then so was everyone elses - and - again see above - the chance was essentially nil no matter who was shooting vs such a target.

Which is why the THEORY that a DC at depth is more fatal is not very germane: you can't set it that deep in most cases, and if you can, you won't guess WHICH of many possible depths to set it at (when he is deep - how deep?)


ASW is hard. Anyone who says different does not understand ASW. And we need to make it less lethal or our subs are just titular subs - not useful instruments.

[el cid again]

ORIGINAL: vettim89

I have to agree that the problem is not with the subs but with the accuracy of the DC. Not being a modder but thinking about it, I think this is where the change should be made. Lethality of DC's is probably about right.

As far as Mousetrap/Hedgehog goes, there are several reasons these weapons were more accurate. The first being that the SONAR operator could feed information to the bridge/CiC as to the subs movement. Hull mounted sonars were blind in an area approximately 30 degrees to either side of the stern. With a DC attack the attacking ship would lose contact with the sub as it passed over it. A wise sub commander would know this and would then time a sprint evasive maneuver just as the ship passed over hoping to not be where the attacking ship's commander had projected the sub to be. Becasue Mousetrap/Hedgehog were Ahead Thrown Weapons, the attacking ship remained in contact with the sub during the attack. the second factor was that the projectiles from this weapons had a very fast sink rate - much faster than DC's. Therfore when the weapons were fired the time to target was much lower. The third factor was that the warheads were direct contact weapons. That is the caused damage by directly impacting the sub's hull. While hits may have been rare, they were devastating. A single 3 " hole in a submerged sub's hull was a big problem.

The other factor that may be playing into the equation is ease of presecution. Is it too easy for DD's et al to find the subs. This was not an easy thing in WWII. The SONAR's were not very accurate and very short ranged. Further, becasue active SONAR was really the only truly effective form in this era, the ship using it gave away its position. The sub drivers knew the approximate position of the ships hunting them and that gave an immense advantage to a sub skipper when trying to get aware.

The ahead throwing weapons were used together with DC in the same run. They would shoot first - and arrive at the target sooner. That meant less time for the sub to evade - to change location. To that add they also would work at ANY depth - and IF they went off you KNEW you hit something. DC are dropped after you pass over - take time to sink - and all the time of getting there and then sinking means the sub is able to evade. They always explode - so you never know if they hit anything - and when they explode they mess up all sonar for some time - you lost contact at that point - 100 per cent of the time.

The preferred tactic is two ships - one standing off - listening to the target while the other makes a run - so you have DATA on where the sub was maneuvering just before the DC went off. The ship making the run sprints - and high speed messes up the sonar too. But the OTHER ship has a clue where he was going - and will be able to reaquire based on that data - and make a run of his own. In RHS sub chasers come in pairs - rated for the pattern of ONE vessel - but twice as many shots - to account for this preferred tactical approach.

[el cid again]

ORIGINAL: ChezDaJez

ORIGINAL: herwin

ORIGINAL: m10bob

On somewhat a similar note, and also according to Clay Blair's SILENT VICTORY, one of the things which assisted allied subs in the Pacific till maybe early '43 was that Japanese DC's had a ridiculous pre-set depth of something like 40 feet(?), as they did not feel subs would be operating any lower when intercepted.
IIRC individual Japanese skippers had to correct this manually, (and against orders) to achieve success in other than shallow water.

Actually not ridiculous at all. That was about optimal. Asdic wasn't very good at localising submarines.

Correct. WWII active sonars had a standard deviation error of approximately 100-150 yards when the searching vessel was within 1000 yards. Passive sonar was even worse especially if it was from a sonobuoy as their was no way to determine bearing. A ship with a steerable receiver could determine a quadrant but bearing accuracy was very poor.

m10bob:

You are on the right track but the Japanese set depth charges based, in part, on the depth capabilities of their own subs. That meant most of their charges were set to 200 feet or less. A US sub was relatively safe below that depth.

An interesting side note to this... a congressman (IIRC) from Illinois conducted a junket tour of the Pacific in 1942 and discovered this fact during an informal briefing. He returned to the States and told a newspaper reporter that our subs were not in danger due to this. The newspaper (Chicago Times?) reported this and the War department became very upset. It has never been determined if the Japanese ever received this information.

Chez

Passive sonabouys were better than this sounds like: set off a noise (drop a DC) - and measure the time of the bounced noise from the target - from different sonabouys. Time = range. If you get several echos you have the exact position in a sense no active sonar ever does.

Active sonar is not just used to measure range - but target speed. Doppler shift tells you if the target is opening or closing the sonar. The amount of change in pitch tells you how great the range rate shift (relative speed) is?

It is not EASY do to ASW - but it is not impossible. A lot has been written about relative ASW that is very misleading: in particular that the Japanese could not do it. When they wanted to - when it was worth the effort - they could. They hated USS Wahoo - and when she was found once again in the Sea of Japan - they set out to get her - using the very things it is written they didn't know how to do and would doctrinally not do: use combined air and sea assets, prosecute the target long enough, coordinate information between commands and services, etc. ASW should be possible but not easy - and should be heavily related to unit experiene - which DOES seem to be the case.

[el cid again]

FYI everyone on a sonar ship or sub learns how to read sonar. The sound pervades the area and the vessel - you hear the outgoing ping and all the echos. You hear the doppler shift. You can come to understand what it means. In a skilled crew it is not even necessary to report - it is understood what each echo (or lack of it) means.

[ChezDaJez]

1) While a submarine IS indeed very vulnerable IF you hit it - a single hole in the pressure hull is often a big problem - they are not "easy to sink" because you cannot hit them.

And this is my point exactly in the game. DC attack accuracy is too great and weapon effect is too little. There are way too many direct hits on subs in the game... and when they are directly hit, the damage is generally less than what should be expected. This does not include those "hits" that produce comments such as "depth charge rattles sub."

2) We have never (in ANY form of WITP) used the REAL depths submarines used tactically. And the apparent "uniform standard" of test depth is NOT uniform in fact - because different nations define it differently. So we get better relative submarine survivability if we use the design depth - calculated from the test depth using national data. Since this ALSO gives us less lethality - it moves us toward solving the problem of submarines are too easy to sink.

Are you planning to use "test depth" to model submarine durability? If so, how will that decrease submarine sinkings? It's my understanding that the game already uses depth ratings to determine durability ratings.

But that is really beside the point. If you increase sub durability, you will make the sub harder to sink but that change, by itself, will not solve the problem. Durability really has nothing to do with the problem. The problem is that subs, in the game, are too easy to hit. How will you fix that? They should be harder to hit but when hit, should be more severely damaged. That is the crux of the matter. Until that is resolved, increasing durability will only mask the true problem.

I confirm that at deeper depths a pressure wave is potentially more dangerous. I don't think it is easy to get close enough however. The deeper a sub goes, the less likely the DC will be set for it. Below a certain depth it becomes IMPOSSIBLE to set for it (the exact depth varies with the DC - but you cannot set a DC for 100 fathoms if it has a 50 fathom limit).

Exactly my point... it's not easy to hit a submerged sub. And it doesn't matter how deep a WWII sub goes. Depth charges from any nation could reach it. The attacking vessel may set their charges too shallow but that isn't a physical limitation of the DC. Japanese DCs using the Type 3 model 1 depth charge pistol had 5 settings: 40, 80, 120, 160 and 200 meters. 200 meters is 656 feet. No US WWII fleet submarine was capable of operating at that depth. The Type 2 pistol was similar with the exception that it lacked the 200 meter setting. Still 160 meters equals 525 feet, again deeper than the test depth of a Balao class.

So let's talk ASW... a topic I am thoroughly familiar and comfortable with.

Your chance of knowing his bearing was much better than your chance of knowing his range - the opposite of radar - sonar bearings are good within a few degrees - but ranges get messed up by lots of things - not all of which were then understood

Bearing accuracy of WWII active sonars was on the order of 15-20 degrees. This was due to the smallness of the receiving head. Range (and we must remember it is slant range) was reasonable accurate at the distances of 1000-2000 yards it was being used.

You chance of knowing his bearing and range was much better than your chance of knowing his depth - almost no depth finding sonar existed - and depth was guessed based on doctrine, tactics, experience or mythology.

Determining an accurate depth is, and was, relatively straight forward. When a sonar "pinged", the transducer head could only pick up echoes within designed horizontal and vertical angles. As the ship moved towards the target, the target echo would be lost at some point. By comparing the last observed slant range with the known reception angle of the transducer head, a reasonalby accurate depth could be determined. It was a simple matter of triangulation to determine the spot on the surface under which the submarine was. You could also take the radar distance between two ships in contact and compare the slant ranges to the target of each and triangulate that way. There were several ways to do it that did not involve mythology. A good sonar operator could also determine a useful depth based on the target's propshaft RPMs and whether the propeller was producing compressed cavitation or not. If he knew themperature gradient of the water through bathythermography, he determine it very accurately.

quote:

ORIGINAL: m10bob

On somewhat a similar note, and also according to Clay Blair's SILENT VICTORY, one of the things which assisted allied subs in the Pacific till maybe early '43 was that Japanese DC's had a ridiculous pre-set depth of something like 40 feet(?), as they did not feel subs would be operating any lower when intercepted.
IIRC individual Japanese skippers had to correct this manually, (and against orders) to achieve success in other than shallow water.


Which may or may not be good analysis. See above about how OUR setting was too deep - that your best shot was at a sub just submerging - for which you MUST have a very shallow setting. It was too shallow for a sub at depth - but then so was everyone elses - and - again see above - the chance was essentially nil no matter who was shooting vs such a target.

Which is why the THEORY that a DC at depth is more fatal is not very germane: you can't set it that deep in most cases, and if you can, you won't guess WHICH of many possible depths to set it at (when he is deep - how deep?)

ASW is hard. Anyone who says different does not understand ASW. And we need to make it less lethal or our subs are just titular subs - not useful instruments.

Sorry, m10bob but your data is incorrect. You may be getting confused with Japanese aerial depth charges which were preset before takeoff and were almost universally set to 40 meters though they could be set deeper. Aerial DCs were set shallow as it was most likely that the sub would have been spotted visually and in the process of diving when an aerial attack was made.

Consider this... a WWII sub operating at periscope depth has a typical keel depth of approximately 60 feet depending upon class. Japanese depth charges, as I related earlier had multiple depth settings and could be set just prior to dropping... in the same manner US depth charges had variable depth settings.

The problem was that the Japanese did not realize how deep a US sub could go and so based their tactics on what they knew... the operating depths of their own submarines. Don't confuse this with the depth capability of the pistol exploders.

El Cid... the fact that a depth charge is more injurious to a sub at depth is a reality. A DC exploding 30 feet from a sub will cause less damage when the sub is near the surface than if that sub is at 400 feet. And at 400 feet, that sub has less time to deal with flooding damage than if near the surface due to the pressure of the water entering that sub.

Once attacked, subs typically dove as deep as they could and it was at those depths that the majority of DC attacks occurred. To say it is not germane shows a keen lack of understanding of submarine evasion techniques and ASW tactics in general. And as I have said, and the research bears out, both Japanese and US depth charges could be set below the maximum operating depth of the subs in question.

ASW can be hard, no question about it. But it is by no means impossible. Not then, not today.

Passive sonabouys were better than this sounds like: set off a noise (drop a DC) - and measure the time of the bounced noise from the target - from different sonabouys. Time = range. If you get several echos you have the exact position in a sense no active sonar ever does.

Active sonar is not just used to measure range - but target speed. Doppler shift tells you if the target is opening or closing the sonar. The amount of change in pitch tells you how great the range rate shift (relative speed) is?

It is not EASY do to ASW - but it is not impossible. A lot has been written about relative ASW that is very misleading: in particular that the Japanese could not do it. When they wanted to - when it was worth the effort - they could. They hated USS Wahoo - and when she was found once again in the Sea of Japan - they set out to get her - using the very things it is written they didn't know how to do and would doctrinally not do: use combined air and sea assets, prosecute the target long enough, coordinate information between commands and services, etc. ASW should be possible but not easy - and should be heavily related to unit experiene - which DOES seem to be the case.

Sonobuoys were routinely employed late in the war by aircraft, not ships. And they were seldom used in the Pacific. Plus most ASW aircraft had but one sonar "listener" with only 2 ears. Even if he were able to listen to two sonobuoys and measure the echo times accurately, he would still need to know the exact positions of the sonobuoys and the explosion.

And using a passive sonobuoy(s) to imitate an active sonar by exploding a charge to create a ping was, and is, extremely inaccurate. First, this could only work if the charge detonated right next to the buoy otherwise you induce a significant range error. Second, if you put the charge close enough to reduce the range error, you would destroy the buoy. Third, the operator could not listen to the buoy when the charge exploded... he would blow out his ears, assuming the sonobuoy wasn't destroyed in the process.

The US Navy never employed this "tactic" you describe. It simply didn't work. There were just too many intangibles, unknowns, and assumptions to be made.

An easier, and much more accurate method, was to listen passively to the submarine noise. If contact was held on multiple buoys, an operator could evaluate the difference in sound strength and come up with a reasonbly accurate AOP.

WWII sonar sets were incapable of displaying doppler values. An operator could hear the change in pitch between the outgoing ping and the received echo and evaluate whether up, down or no doppler but he had no means of measuring that change in pitch and therefore could not calculate a reasonable target speed without a target plot. In WWII. most operators relied on "turncounting" to determine a speed. That is he counted the number of propshaft revolutions he heard and applied a TPK (turns per knot) value. If the sub's prop was turning 100 RPM and the TPK was 10, the sub speed was 10kts.

You are correct in that the Japanese did have the ASW know-how to prosecute subs but their main failing was not in equipping their ASW vessels with radar. Fully 80% of Japanese ASW ships did not have radar. Japanese airborne ASW efforts were just beginning to become effective when the war ended. They had a very good MAD set with a detectable slant range of 280 meters... more than the equivalent Brit or US system had... and they had developed a 5-plane tactic for using it that the US adopted for a short period after the war.

FYI everyone on a sonar ship or sub learns how to read sonar. The sound pervades the area and the vessel - you hear the outgoing ping and all the echos. You hear the doppler shift. You can come to understand what it means. In a skilled crew it is not even necessary to report - it is understood what each echo (or lack of it) means.

I'ld certainly like to know what ships did that. Sonar, especially passive, is a highly perishable skill. I believe that there are plenty of former Navy men on this forum that would dispute this claim. Men on a ship can certainly hear the ping but there is no way they will hear the echo. And even if they did, they wouldn't know up doppler from down.

BTW, Cid... what ships did you serve on in the Navy? I seem to remember you saying that you were an ET. Is that correct?

Chez

[el cid again]

ORIGINAL: ChezDaJez

1) While a submarine IS indeed very vulnerable IF you hit it - a single hole in the pressure hull is often a big problem - they are not "easy to sink" because you cannot hit them.

And this is my point exactly in the game. DC attack accuracy is too great and weapon effect is too little. There are way too many direct hits on subs in the game... and when they are directly hit, the damage is generally less than what should be expected. This does not include those "hits" that produce comments such as "depth charge rattles sub."


REPLY: I think you are correct in a sense - only hits count - but I interpret "hit" for a DC as meaning "close enough to cause damage" - and if that is true I think the "hits" are too effective. I have gone over to a reduced damage system for DC and other AS weapons - and it seems not to have made very much difference - but it cannot have hurt survivability. My goal is to have damage inflicting attacks occur less often and be fatal less often. I don't know if GG meant a "hit" to include near misses or not - but I think of them that way.

2) We have never (in ANY form of WITP) used the REAL depths submarines used tactically. And the apparent "uniform standard" of test depth is NOT uniform in fact - because different nations define it differently. So we get better relative submarine survivability if we use the design depth - calculated from the test depth using national data. Since this ALSO gives us less lethality - it moves us toward solving the problem of submarines are too easy to sink.

Are you planning to use "test depth" to model submarine durability? If so, how will that decrease submarine sinkings? It's my understanding that the game already uses depth ratings to determine durability ratings.

REPLY: The SYSTEM indeed does use depth. But it is not the RIGHT depth. That is - different nations used different definitions of "operating depth" - and in combat submarines really used "test depth" - and even exceeded this and survived in numbers of cases. What I have done is find a way to have a uniform standard - actually "design depth" - which is just below true crush depth - and since we can figure this out on a uniform basis - it means that subs will be relatively better rated. Since it also is greater than operating depth, significantly so, it means there will be many fewer hits. US and Japan will get 50 per cent higher ratings. UK was to get 75 per cent - based on theory - but I just got better data (from the Dutch of all places - they ran the same subs) - and so they will get more but not exactly that percentage. The Dutch get just over twice as much. The Germans will get three times as much. This means that national and class differences will be better reflected in the chance of scoring ANY hits at all.

But that is really beside the point. If you increase sub durability, you will make the sub harder to sink but that change, by itself, will not solve the problem. Durability really has nothing to do with the problem. The problem is that subs, in the game, are too easy to hit. How will you fix that? They should be harder to hit but when hit, should be more severely damaged. That is the crux of the matter. Until that is resolved, increasing durability will only mask the true problem.

REPLY: OK - because the ASW algorithm uses depth data IN THE FORM of the durability rating - increasing it makes the sub harder to hit and more likely to survive. It is classic GG - very simple - even crude - but in the ball park. I don't agree with your position that a hit should do more damage - because for me a "hit" is only rarely a direct hit - it is "anything close enough to do damge" - which GG brilliantly covers with his die rolls - you can get a lot of damage or a little - you can cause special damage too - and that might cause still more damage (e.g. fires or flooding).

I confirm that at deeper depths a pressure wave is potentially more dangerous. I don't think it is easy to get close enough however. The deeper a sub goes, the less likely the DC will be set for it. Below a certain depth it becomes IMPOSSIBLE to set for it (the exact depth varies with the DC - but you cannot set a DC for 100 fathoms if it has a 50 fathom limit).

Exactly my point... it's not easy to hit a submerged sub. And it doesn't matter how deep a WWII sub goes. Depth charges from any nation could reach it. The attacking vessel may set their charges too shallow but that isn't a physical limitation of the DC. Japanese DCs using the Type 3 model 1 depth charge pistol had 5 settings: 40, 80, 120, 160 and 200 meters. 200 meters is 656 feet. No US WWII fleet submarine was capable of operating at that depth. The Type 2 pistol was similar with the exception that it lacked the 200 meter setting. Still 160 meters equals 525 feet, again deeper than the test depth of a Balao class.

REPLY: This is essentially incorrect data, and in several different ways. First - more than a few DC could not be set to work at anything like those depths. Second - German submarines had a defacto crush depth (based on enough data to be statistically valid) that was NEVER less than 200 meters - and sometimes was as great as 280 meters (and I have proposed to use 230 meters here - 750 feet - as a reasonable compromise). German operating depth was de facto about 250 feet - its theoretical design depth about 500 feet - and its actual practical depth was significantly higher than that in all cases. [The actual operating depth was 75 meters and design depth 150 meters, but the building standards were far too conservative - and never less than 200 meters according to comprehensive Allied post war analysis - usually somewhat more.] This is an exceptional case only applicable to RHS - other forms of WITP don't have die Erste Monsoon boats - so what matters for us - mostly - is two things: (1) many DC didn't work at all at great depths and even more important (2) even if they did they were almost never set right. Analysis shows that hits below a relatively shallow depth were so rare that they are zero if you count hits per 100 patterns.

So let's talk ASW... a topic I am thoroughly familiar and comfortable with.

Your chance of knowing his bearing was much better than your chance of knowing his range - the opposite of radar - sonar bearings are good within a few degrees - but ranges get messed up by lots of things - not all of which were then understood

Bearing accuracy of WWII active sonars was on the order of 15-20 degrees. This was due to the smallness of the receiving head. Range (and we must remember it is slant range) was reasonable accurate at the distances of 1000-2000 yards it was being used.

REPLY: OK - I am also comfortable here. I once got to see the second most primitive active sonar of all time. [The most primitive was when WWI sub chaser's had men pound on the hull with a sledgehammer and use a stopwatch to get the echo delay.] This was used by the Ethopian Navy - and was more or less a 1930s vintage US hydrophone (a T shaped device) modified with a conical attachment across which was strecthed a drum head - which they then hit with a rubber mallot. They too timed the echo with a stopwatch - but they could turn the hydrophone to get a better sense of the bearing! While it is true that many active sonars didn't give great readings - skilled operators should be trained to read ten times the scale markings. [In ECM I call 5 degree markings at half degree incriments - and I am always within 1 degree - if radar is tracking the same target - which I did to measure my error rate; in the case of old sonar I call it to 2 degrees and if we can calibrate with other means I will be within 3 or 4 degrees of true.] Range - on the other hand - is a matter of many factors - and it is not a strait line as radar is (almost). Sound ALWAYS bends. If ranges are typically 1000-2000 yards in that era - sonar is a fickel creature - and in ideal sound conditions it will be several times that - while in horrible ones it is more or less nil. At longer ranges the bending is a greater problem. As with radar the length of the pulse limits your accuracy - but the practical errors in sonar are ALWAYS several times that - sometimes many times that - while in radar they are only that.

You chance of knowing his bearing and range was much better than your chance of knowing his depth - almost no depth finding sonar existed - and depth was guessed based on doctrine, tactics, experience or mythology.

Determining an accurate depth is, and was, relatively straight forward. When a sonar "pinged", the transducer head could only pick up echoes within designed horizontal and vertical angles. As the ship moved towards the target, the target echo would be lost at some point. By comparing the last observed slant range with the known reception angle of the transducer head, a reasonalby accurate depth could be determined. It was a simple matter of triangulation to determine the spot on the surface under which the submarine was. You could also take the radar distance between two ships in contact and compare the slant ranges to the target of each and triangulate that way. There were several ways to do it that did not involve mythology. A good sonar operator could also determine a useful depth based on the target's propshaft RPMs and whether the propeller was producing compressed cavitation or not. If he knew themperature gradient of the water through bathythermography, he determine it very accurately.

REPLY: This indeed sounds like somethign you might be told in WWII - at least the first part. It is more or less technical mythology all by itself - given that it is not literally true - ever. You are thinking - and they thought of - sonar signals as "strait lines" - a sound analog for radar - but it isn't - and it cannot be due to the physics involved. The reason this is somewhat useful is that at very short ranges it is approximately true - but my focus is on the "approximately" - and the difference between "true" and "approximately true" is the error you will get ON TOP of whatever errors you make in measurement. It is worse than that makes it sound like too - because the actual angles change with water conditions - which are not just temperature - as you no doubt know (but failed to say). We may be able to agree because you used the term "reasonably accurate" - and because it is clear you are thinking of average conditions. The problem IRL is that average conditions are not typical - it is often a lot better or worse than average - and if it is better the ranges are no longer small enough these rules of thumb work so well - while if it is a lot worse you just don't have data to play with. You also used the qualifier "good operator" - and that makes you right - but a typical ASW ship had zero of these - and most of the rest only one - so maintaining a continuous watch (ASW needs to happen over days of time - not the brief things in WITP) - is not easy for most ships (stations, subs, planes, whoever has the sonar in question). I will stipulate the reason for lack of knowledge on the bridge is mostly lack of operator knowledge on the sonar - but that is the normal case - and the reason that the vast majority of ASW vessels that DID get a target never hit it. The inverse is probably why USS England only needed one pass to inflict fatal damage - every time. Those Ethopians could actually find a submarine with their horrible equipment - because they went out and practiced on various underwater targets. [I hate to think of taking on anything better than a Chinese Romeo - but that is another story - operator skill is more critical than equipment quality. Submarines were even detected in WWI by banging on the hull - albiet rarely.]

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[el cid again]

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Sorry, m10bob but your data is incorrect. You may be getting confused with Japanese aerial depth charges which were preset before takeoff and were almost universally set to 40 meters though they could be set deeper. Aerial DCs were set shallow as it was most likely that the sub would have been spotted visually and in the process of diving when an aerial attack was made.

Consider this... a WWII sub operating at periscope depth has a typical keel depth of approximately 60 feet depending upon class. Japanese depth charges, as I related earlier had multiple depth settings and could be set just prior to dropping... in the same manner US depth charges had variable depth settings.

The problem was that the Japanese did not realize how deep a US sub could go and so based their tactics on what they knew... the operating depths of their own submarines. Don't confuse this with the depth capability of the pistol exploders.

REPLY: This is widely reported - but not supported by the data. US and Japanese submarines were comparable - and comparable by age - so that a 1920s vintage boat is less able to dive than a 1940s era one. When we captured Japanese submarines in 1945, we "knew" there "was nothing we could learn" to such an extent we failed to test the guppy's before we scuttled them. Yet the German boats we DID test turned out to have a bad design, and Norman Friedman writes (US Submarines Since WWII) the Japanese boats were "based on superior hydrodynamic research." Our sub design for a post WWII boat was so hopeless it was not put into production. Most boats designed since look a lot more like the Japanese guppys. And NONE of our boats could dive like they could - although the very last mark of the Fleet boats got close.

You are right - Japanese DC had several settings - and mostly they were set wrong rather than they could not be set right. But few DC of the set fuse type (vice proxcimity fuse) could reach the actual operating depth of some submarines - and deep sinking DC were also the least likely to hit - because the time to sink meant the sub was no longer near the datum point. Deep set DC had a success rate approaching none at all.

El Cid... the fact that a depth charge is more injurious to a sub at depth is a reality. A DC exploding 30 feet from a sub will cause less damage when the sub is near the surface than if that sub is at 400 feet. And at 400 feet, that sub has less time to deal with flooding damage than if near the surface due to the pressure of the water entering that sub.

REPLY: This is quite true. The problem is - it is almost impossible to get within 10 meters of a deep submarine. It is either drifting or moving under power, if the latter it may be moving ahead or reverse and it may be turning port or starboard. A long sinking time = more time to move = more error IF you had the right location to begin with. This is more or less why DC are dropped in patterns: You fire a sort of circle around the datum point - or the calculated target location point given what you know/guess he is doing - and if it is big enough - you also drop one in the very center of the "circle" (which is not exactly a circle). You do that so no matter where he moves there is an area in which he is likely to be near one (or two) of your DC. But if his movement rate is fast enough - or (more likely) if you calculated wrong - the entire pattern is not close enough. Luck is a factor - he might move INTO your missed pattern for example - and maybe luck is as big a factor as science in most attacks. Even today: witness RN in 1982. Facing but one sub with most of the best ASW ships and aircraft in the fleet - they only localized it once - and failed to damage it even then. But they THOUGHT they had localized it about 200 times.

Once attacked, subs typically dove as deep as they could and it was at those depths that the majority of DC attacks occurred. To say it is not germane shows a keen lack of understanding of submarine evasion techniques and ASW tactics in general. And as I have said, and the research bears out, both Japanese and US depth charges could be set below the maximum operating depth of the subs in question.

ASW can be hard, no question about it. But it is by no means impossible. Not then, not today.

REPLY: I have been able to work with original as well as derived documents. What passes as common "knowledge" for WWII era ASW is often remarkably far from the truth: the idea that no submarine could dive below 200 meters being a great example - and one thing German sub captains exploited. In The Enemy Below the author - who knew somethign of the subject - has this exchange:

Junior officer: "The bottom is xyz feet - can he go that deep?"

Captain: "He would like us to think he can't."

When you "know" he cannot go that deep - and he does - you "know" he is "dead" - so you stop hunting. Pretty classic if you read German survivor accounts. Some German submarines substantially exceeded 900 feet - not without a bit of worry no doubt - and came back to tell us about it.

It may be we will not agree: if ASW was not truly nearly impossible, why did the best of NATO do so badly in 1982? And why is a 2007 era USNI Proceedings able to report it has become "routine" for "minor navy conventional submarines" to detect, localize and fire upon US carriers? We "didn't need" to keep ASW destroyers - and almost have got rid of the frigates - and we took the ASW out of the fixed wing ASW planes on carriers (they carry fuel and cargo now) - and reduced helos to only 4 - and put the few surviving patrol planes onto other WOT duties - they hunt things at night in the desert with infra red sensors - anything but ASW. A ship does not get the kind of practice it needs often enough to matter (hopefully there are exceptions -but I am not aware of any at all outside the sub force). ASW requires a lot of effort - it is expensive - unless the enemy is very stupid or very unlucky.

Passive sonabouys were better than this sounds like: set off a noise (drop a DC) - and measure the time of the bounced noise from the target - from different sonabouys. Time = range. If you get several echos you have the exact position in a sense no active sonar ever does.

Active sonar is not just used to measure range - but target speed. Doppler shift tells you if the target is opening or closing the sonar. The amount of change in pitch tells you how great the range rate shift (relative speed) is?

It is not EASY do to ASW - but it is not impossible. A lot has been written about relative ASW that is very misleading: in particular that the Japanese could not do it. When they wanted to - when it was worth the effort - they could. They hated USS Wahoo - and when she was found once again in the Sea of Japan - they set out to get her - using the very things it is written they didn't know how to do and would doctrinally not do: use combined air and sea assets, prosecute the target long enough, coordinate information between commands and services, etc. ASW should be possible but not easy - and should be heavily related to unit experiene - which DOES seem to be the case.

Sonobuoys were routinely employed late in the war by aircraft, not ships. And they were seldom used in the Pacific. Plus most ASW aircraft had but one sonar "listener" with only 2 ears. Even if he were able to listen to two sonobuoys and measure the echo times accurately, he would still need to know the exact positions of the sonobuoys and the explosion.

And using a passive sonobuoy(s) to imitate an active sonar by exploding a charge to create a ping was, and is, extremely inaccurate. First, this could only work if the charge detonated right next to the buoy otherwise you induce a significant range error. Second, if you put the charge close enough to reduce the range error, you would destroy the buoy. Third, the operator could not listen to the buoy when the charge exploded... he would blow out his ears, assuming the sonobuoy wasn't destroyed in the process.

The US Navy never employed this "tactic" you describe. It simply didn't work. There were just too many intangibles, unknowns, and assumptions to be made.

REPLY: Most of this I cannot discuss - it is illegal. But a few things I can say:

1) Blimps used sonabouys in PTO - they had no other sonar at all - but they did have MAD. Early in the war a variation of the B-18 also used MAD and sonabouys out of Panama. Since you don't know about this use in PTO - you may not be familiar with the actual tactics they used. This was later used as the basis for other tactics in the Cold War era - but I am required to refer interesed persons to unclassified materials - and may neither confirm nor deny any details. So I won't. But I didn't say anything that isn't true in principle - and wether or not it worked is not something we can talk about.

An easier, and much more accurate method, was to listen passively to the submarine noise. If contact was held on multiple buoys, an operator could evaluate the difference in sound strength and come up with a reasonbly accurate AOP.

WWII sonar sets were incapable of displaying doppler values. An operator could hear the change in pitch between the outgoing ping and the received echo and evaluate whether up, down or no doppler but he had no means of measuring that change in pitch and therefore could not calculate a reasonable target speed without a target plot. In WWII. most operators relied on "turncounting" to determine a speed. That is he counted the number of propshaft revolutions he heard and applied a TPK (turns per knot) value. If the sub's prop was turning 100 RPM and the TPK was 10, the sub speed was 10kts.

REPLY: I did not say that doppler was visually displayed. I confirm you can hear it. But THAT IS a way to measure it. Possibly - I am musician - it helps if you have some sense of what a pitch is? The amount of doppler tells you the range rate change. I once designed an early computer game [The Enemy Below] in which the player was the US DE operator. I gave the sonar simulator real doppler - and I gave the player keyboard controls as well as other controls. In one game a tester - who had many games of experience - lost all vistual display and non keyboard controls. Instead of stopping the test - he had finally got a good position to attack from - he made the run in - hit the drop key at the right moment - and was rewarded by the audio of a successful hit pattern. He had learned how to know the position of the submarine simply by listening to the pings and echos - with no display at all (not something I intended players to have to do - ever). Doppler is an idea - and you have ears and a brain - so at least in theory you can use the information if you hear it. I submit that is better than NOT using the data.

You are correct in that the Japanese did have the ASW know-how to prosecute subs but their main failing was not in equipping their ASW vessels with radar. Fully 80% of Japanese ASW ships did not have radar. Japanese airborne ASW efforts were just beginning to become effective when the war ended. They had a very good MAD set with a detectable slant range of 280 meters... more than the equivalent Brit or US system had... and they had developed a 5-plane tactic for using it that the US adopted for a short period after the war.

FYI everyone on a sonar ship or sub learns how to read sonar. The sound pervades the area and the vessel - you hear the outgoing ping and all the echos. You hear the doppler shift. You can come to understand what it means. In a skilled crew it is not even necessary to report - it is understood what each echo (or lack of it) means.

I'ld certainly like to know what ships did that. Sonar, especially passive, is a highly perishable skill. I believe that there are plenty of former Navy men on this forum that would dispute this claim. Men on a ship can certainly hear the ping but there is no way they will hear the echo. And even if they did, they wouldn't know up doppler from down.

BTW, Cid... what ships did you serve on in the Navy? I seem to remember you saying that you were an ET. Is that correct?

Chez
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REPLY: Once again mythology is working - no subject has more of it than the "lack of Japanese radar" - by 1944 it was SOP to fit an ASW ship - and many other ships - even merchant ships - with radar. These radars were often used in passive mode - as ESM - since by then the US had radar on everything - ESM operation gave a greater detection range than active operation - and the radars would fail less often (the active tubes had a very short life). This may have contributed to the perception of lack of radar. The senior surviving officer of Shinano - in a book of that title - a medical doctor (and a captain) - says the American use of radar was pervasive and routinely exploited - and I certainly confirm that was US SOP in the Cold War era. [I say we are "radioactive" and that we "radiate with practically everything practically all the time" as a way to get a sense of what we do]

You misunderstood my sonar - I meant ACTIVE sonar - you can not hear an echo of a ping never sent out. But ACTIVE sonar is very loud - it fills the sea and the ship - and the echo is loud enough to hear. It is not unusual for people to understand what they just heard before any report can be made. Things like "we just picked up a target" - "the target is closing range" - "the target is very close" - etc. are entirely obvious to anyone who has been there before.